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  • 1. Aaro, Sven
    et al.
    Sjöström, Håkan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Airborne and ground geophysics used for regional tectonic analysis2003In: IUGG 2003, Sapporo, Japan: No GAV.06/10P/A11-004, B260., 2003Conference paper (Refereed)
  • 2.
    Abadi, Mehrdad Sardar
    et al.
    Leibniz Inst Appl Geophys, LIAG, Rock Phys & Borehole Geophys, Hannover, Germany..
    Voeten, Dennis F. A. E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Kulagina, Elena, I
    Russian Acad Sci, Ufa Fed Res Ctr, Inst Geol, Ufa, Russia..
    Boulvain, Frederic
    Univ Liege, Dept Geol, Lab Petrol Sedimentaire, Bat B20, Liege, Belgium..
    Da Silva, Anne-Christine
    Univ Liege, Dept Geol, Lab Petrol Sedimentaire, Bat B20, Liege, Belgium..
    A comment on overlooked storm sensitivity of the carbonate factory recorded in the Mississippian Mobarak Formation (Alborz Mountains, Iran)2022In: Geological Journal, ISSN 0072-1050, E-ISSN 1099-1034, Vol. 57, no 10, p. 4388-4392Article in journal (Other academic)
    Abstract [en]

    New interpretations of depositional palaeoenvironments in the Mississippian (Lower Carboniferous) Mobarak Formation (Alborz Mountains, Iran) suggest a significant and persistent influence of storms. This deviates from previous conclusions that these deposits recorded mounds, patch reefs, and extensive lagoons deposited under stagnant environmental conditions. We here clarify and discuss the origin and nature of this misconception by explaining "unexpected" observations that are informed by outdated interpretations of the depositional environment of the Mobarak Formation. This evaluation offers the context required for appropriately interpreting and correlating Mississippian depositional records across the Alborz Basin.

  • 3.
    Abdelmaksoud, Ahmed
    et al.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates.;Assiut Univ, Dept Geol, Assiut, Egypt..
    Ali, Mohammed Y.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Al Suwaidi, Aisha
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Petroleum system of the fold-and-thrust belt of the United Arab Emirates: New insights based on 1D and 2D basin modeling2023In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 158, article id 106567Article in journal (Refereed)
    Abstract [en]

    The hydrocarbon potential of the fold-and-thrust belt (FTB) in the United Arab Emirates (UAE)-Oman mountains has received limited attention to date, leading to a poor understanding of the petroleum systems in this region. Despite the existence of hydrocarbon fields within the FTB, the source rock potential has not been adequately studied. This study aims to address this knowledge gap using 1D and 2D basin modeling approaches to evaluate the petroleum system of the FTB. In addition, gas chromatographs are also used to correlate hydrocarbon occurrences with their source rock. This study's findings identify the Silurian, Upper Cretaceous, Paleocene-Eocene, and Oligocene formations as the primary source rocks in the study area. Silurian shales, encountered in a well in the northern UAE, are currently considered overmature. The Cenozoic source rocks exhibit a spectrum of Total Organic Carbon (TOC) content, ranging from less than 1 to as high as 2 wt%, leading to variable degrees of expulsion efficiency. The maturity of these rocks varies based on their position in relation to the FTB and foredeep, with increasing maturity towards the north. The Upper Cretaceous sequences display low TOC and Hydrogen Index, indicating very low expulsion efficiency. The present-day distribution of maturity is largely influenced by Late Cretaceous and Oligocene-Miocene compressional events that affected the northern and northeastern Arabian Plate. This analysis shows that hydrocarbon expulsion from the Silurian source rocks was initiated during the Middle-Late Jurassic. These hydrocarbons are presumed to have migrated through Upper Permian, Jurassic, and Lower and middle Cretaceous reservoirs. Westward hydrocarbon migration, towards a regional bulge, may have also occurred following compressional events that resulted in lithospheric flexure and formation of the foreland basin. Notably, certain exceptions to migration towards the bulge include structural entrapment of hydrocarbons beneath the main frontal thrust zone of FTB and some structural traps beneath the Lower Fiqa Formation.

  • 4. Abouessa, A.
    et al.
    Morad, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    An integrated study of diagenesis and depositional facies in tidal sandstones: Hawaz Formation (middle Ordovician), Murzuq Basin, Libya2009In: Journal of Petroleum Geology, ISSN 0141-6421, E-ISSN 1747-5457, Vol. 32, no 1, p. 39-65Article in journal (Refereed)
  • 5. Adolphi, Florian
    et al.
    Muscheler, Raimund
    Svensson, Anders
    Aldahan, Ala
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Beer, Jurg
    Sjolte, Jesper
    Bjorck, Svante
    Matthes, Katja
    Thieblemont, Remi
    Persistent link between solar activity and Greenland climate during the Last Glacial Maximum2014In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 7, no 9, p. 662-666Article in journal (Refereed)
    Abstract [en]

    Changes in solar activity have previously been proposed to cause decadal- to millennial-scale fluctuations in both the modern and Holocene climates(1). Direct observational records of solar activity, such as sunspot numbers, exist for only the past few hundred years, so solar variability for earlier periods is typically reconstructed from measurements of cosmogenic radionuclides such as Be-10 and C-14 from ice cores and tree rings(2,3). Here we present a high-resolution Be-10 record from the ice core collected from central Greenland by the Greenland Ice Core Project (GRIP). The record spans from 22,500 to 10,000 years ago, and is based on new and compiled data(4-6). Using C-14 records(7,8) to control for climate-related influences on Be-10 deposition, we reconstruct centennial changes in solar activity. We find that during the Last Glacial Maximum, solar minima correlate with more negative delta O-18 values of ice and are accompanied by increased snow accumulation and sea-salt input over central Greenland. We suggest that solar minima could have induced changes in the stratosphere that favour the development of high-pressure blocking systems located to the south of Greenland, as has been found in observations and model simulations for recent climate(9,10). We conclude that the mechanism behind solar forcing of regional climate change may have been similar under both modern and Last Glacial Maximum climate conditions.

  • 6.
    Agbaje, Oluwatoosin B. A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Department of Earth and Environmental Sciences, Macquarie University, Sydney, Australia; Department of Biological Sciences, Macquarie University, Sydney, Australia.
    Brock, Glenn A.
    Department of Biological Sciences, Macquarie University, Sydney, Australia; State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an, 710069, China.
    Zhang, Zhifei
    State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an, 710069, China.
    Duru, Kingsley C.
    Department of Technology for Organic Synthesis, Ural Federal University, Yekaterinburg, Russia; Department of Biomedical Sciences, Macquarie University, Sydney, Australia.
    Liang, Yue
    State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an, 710069, China.
    George, Simon C.
    Department of Earth and Environmental Sciences, Macquarie University, Sydney, Australia.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an, 710069, China.
    Biomacromolecules in recent phosphate-shelled brachiopods: identification and characterization of chitin matrix2021In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 56, no 36, p. 19884-19898Article in journal (Refereed)
    Abstract [en]

    Phosphate-shelled brachiopods differ in filter-feeding lifestyle, with Lingula anatina an active infaunal burrower, and Discinisca tenuis a shallow marine epibenthic animal. The shells of these animals are built of organophosphatic constituents, the organic fibres/sheets reinforced with calcium phosphate to provide a sophisticated ultrastructural robustness. This investigation examined the nature of the organic fibres in order to improve understanding of how living organisms produce hierarchically structured biomaterials. Unlike powdered samples commonly used in previous studies, organic fibres were isolated for the first time and the shell fractions were purified, in order to study the content and nature of the biopolymer fibres. Biochemical methods including Calcofluor staining revealed a chitin matrix. Ultrastructural analysis, thermal gravimetric analysis, and spectroscopic analyses show that the core polysaccharide framework is composed of layers of β-chitin sheets and/or fibrils that are coated with a fibrous organic matrix. There is more chitin matrix in the L. anatina shells (26.6 wt.%) compared to the D. tenuis shells (12.9 wt.%). Taken together, the data show that the chitin matrix contributes to increased skeletal strength, making L. anatina highly adapted for life as an active burrower. In comparison, D. tenuis contains less chitin and lives as attached epibenthos in a shallow marine environment.

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  • 7.
    Agbaje, Oluwatoosin B. A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Department of Earth and Environmental Sciences and MQ Marine Research Centre, Macquarie University, Sydney, Australia; Department of Biological Sciences, Macquarie University, Sydney, Australia.
    George, Simon C.
    Department of Earth and Environmental Sciences and MQ Marine Research Centre, Macquarie University, Sydney, Australia.
    Zhang, Zhifei
    State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments, Department of Geology, Northwest University, Xi'an, China.
    Brock, Glenn A.
    Department of Biological Sciences, Macquarie University, Sydney, Australia; State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments, Department of Geology, Northwest University, Xi'an, China.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments, Department of Geology, Northwest University, Xi'an, China.
    Characterization of organophosphatic brachiopod shells: spectroscopic assessment of collagen matrix and biomineral components2020In: RSC Advances, E-ISSN 2046-2069, Vol. 10, p. 38456-38467Article in journal (Refereed)
    Abstract [en]

    The shells of linguloid brachiopods such as Lingula and Discinisca are inorganic–organic nanocomposites with a mineral phase of calcium phosphate (Ca-phosphate). Collagen, the main extracellular matrix in Ca-phosphatic vertebrate skeletons, has not previously been clearly resolved at the molecular level in organophosphatic brachiopods. Here, modern and recently-alive linguliform brachiopod shells of Lingula and Discinisca have been studied by microRaman spectroscopy, Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermal gravimetric analysis. For the first time, biomineralized collagen matrix and Ca-phosphate components were simultaneously identified, showing that the collagen matrix is an important moiety in organophosphatic brachiopod shells, in addition to prevalent chitin. Stabilized nanosized apatitic biominerals (up to ∼50 nm) permeate the framework of organic fibrils. There is a ∼2.5-fold higher wt% of carbonate (CO32−) in Lingula versus Discinisca shells. Both microRaman spectroscopy and infrared spectra show transient amorphous Ca-phosphate and octacalcium phosphate components. For the first time, trivalent moieties at ∼1660 cm−1 and divalent moieties at ∼1690 cm−1 in the amide I spectral region were identified. These are related to collagen cross-links that are abundant in mineralized tissues, and could be important features in the biostructural and mechanical properties of Ca-phosphate shell biominerals. This work provides a critical new understanding of organophosphatic brachiopod shells, which are some of the earliest examples of biomineralization in still-living animals that appeared in the Cambrian radiation.

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  • 8.
    Agic, Heda
    et al.
    Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA..
    Hogstrom, Anette E. S.
    UiT Arctic Univ Norway, Arctic Univ Museum Norway, Tromso, Norway..
    Jensen, Soren
    Univ Extremadura, Area Paleontol, Badajoz, Spain..
    Ebbestad, Jan Ove R.
    Uppsala University, Music and Museums, Museum of Evolution.
    Vickers-Rich, Patricia
    Monash Univ, Sch Earth Atmosphere & Environm, Clayton, Vic, Australia.;Swinburne Univ Technol, Sch Sci, Dept Chem & Biotechnol, Hawthorn, Vic, Australia..
    Hall, Michael
    Monash Univ, Sch Earth Atmosphere & Environm, Clayton, Vic, Australia..
    Matthews, Jack J.
    Oxford Univ Museum Nat Hist, Oxford, England..
    Meinhold, Guido
    TU Bergakad Freiberg, Inst Geol, Freiberg, Germany.;Univ Gottingen, Dept Sedimentol & Environm Geol, Gottingen, Germany..
    Hoyberget, Magne
    Rennesveien 14, Mandal, Norway..
    Taylor, Wendy L.
    Univ Cape Town, Dept Geol Sci, Rondebosch, South Africa..
    Late Ediacaran occurrences of the organic-walled microfossils Granomarginata and flask-shaped Lagoenaforma collaris gen. et sp. nov.2022In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 159, no 7, p. 1071-1092, article id PII S0016756821001096Article in journal (Refereed)
    Abstract [en]

    New occurrences of flask-shaped and envelope-bearing microfossils, including the predominantly Cambrian taxon Granomarginata, are reported from new localities, as well as from earlier in time (Ediacaran) than previously known. The stratigraphic range of Granomarginata extends into the Cambrian System, where it had a cosmopolitan distribution. This newly reported Ediacaran record includes areas from Norway (Baltica), Newfoundland (Avalonia) and Namibia (adjacent to the Kalahari Craton), and puts the oldest global occurrence of Granomarginata in the Indreelva Member (< 563 Ma) of the Stahpogieddi Formation on the Digermulen Peninsula, Arctic Norway. Although Granomarginata is rare within the assemblage, these new occurrences together with previously reported occurrences from India and Poland, suggest a potentially widespread palaeogeographic distribution of Granomarginata through the middle-late Ediacaran interval. A new flask-shaped microfossil Lagoenaforma collaris gen. et sp. nov. is also reported in horizons containing Granomarginata from the Stahpogieddi Formation in Norway and the Dabis Formation in Namibia, and flask-shaped fossils are also found in the Gibbett Hill Formation in Newfoundland. The Granomarginata-Lagoenaforma association, in addition to a low-diversity organic-walled microfossil assemblage, occurs in the strata postdating the Shuram carbon isotope excursion, and may eventually be of use in terminal Ediacaran biostratigraphy. These older occurrences of Granomarginata add to a growing record of body fossil taxa spanning the Ediacaran-Cambrian boundary.

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    FULLTEXT01
  • 9.
    Agic, Heda
    et al.
    Univ Durham, Dept Earth Sci, Durham, England..
    Jensen, Soren
    Univ Extremadura, Fac Ciencias, Area Paleontol, Badajoz, Spain..
    Meinhold, Guido
    TU Bergakad Freiberg, Inst Geol, Freiberg, Germany.;Univ Gottingen, Dept Sedimentol & Environm Geol, Gottingen, Germany..
    Hogstrom, Anette E. S.
    Arctic Univ Museum Norway, UiT The Arctic Univ Norway, Tromso, Norway..
    Ebbestad, Jan Ove R.
    Uppsala University, Music and Museums, Museum of Evolution.
    Hoyberget, Magne
    Palacios, Teodoro
    Univ Extremadura, Fac Ciencias, Area Paleontol, Badajoz, Spain..
    Taylor, Wendy L.
    Univ Cape Town, Dept Geol Sci, Rondebosch, South Africa..
    Life through an Ediacaran glaciation: Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway2024In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 635, article id 111956Article in journal (Refereed)
    Abstract [en]

    New organic-walled microfossil (OWM) assemblages are reported from upper Neoproterozoic glacial and interglacial siliciclastic deposits in Finnmark, northern Norway. A nearly continuous sedimentary succession of the Vestertana Group contains two glaciogenic units, the Smalfjorden and Mortensnes formations, interpreted as end-Cryogenian Marinoan and Ediacaran glaciations, respectively. We investigated the OWM record in the Nyborg, Mortensnes, and St ' ahpogieddi formations to assess the impact of a glacial interval on the diversity of microscopic eukaryotes. A modified acid-extraction technique was applied to recover OWM from the diamictite matrix. The upper Nyborg Formation contains morphologically complex Doushantuo-Pertatataka acritarchs (DPA), restricting the age of the Nyborg Formation to early-mid Ediacaran. DPA occur below the dolostones that record a negative carbon isotope excursion correlated with the Shuram anomaly and below a glacial diamictite. A decline in species richness and compositional change is observed in the Mortensnes glacial assemblage. DPA are replaced by bacterial filaments and cell aggregates. The overlying Indreelva Member, St ' ahpogieddi Formation contains Ediacara-type biota and palaeopascichnids, but only a depauperate OWM assemblage of leiosphaerids and flask-shaped microfossils characteristic of the late Ediacaran.The succession of assemblages in the Vestertana Group demonstrates a turnover from large eukaryotic OWM to a microbial community in the glacial interval, to a low diversity post-glacial assemblage during the rise of macroscopic life. We compared the Vestertana record to global DPA occurrences. Although one DPA assemblage zone postdates the Shuram excursion, no DPA occur above Ediacaran glacial diamictites in successions where those deposits are present. Considering this, and the community changes in the Vestertana succession, we suggest that DPA were affected by the onset of an Ediacaran glaciation. Lastly, we combined the biostratigraphic markers in the Vestertana Group to constrain the age of the Mortensnes diamictite.

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  • 10.
    Agić, Heda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton2016In: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 40, no 3, p. 343-356Article in journal (Refereed)
    Abstract [en]

    The Proterozoic-Phanerozoic transition records a general trend of decrease in phytoplankton cell size, in contrast tothe earlier and much larger Ediacaran acritarchs. Particularly minute, unornamented but sculptured organic-walledmicrofossils have been recovered from the lower Cambrian Lükati Formation in northern Estonia. The lack of anysignificant thermal alteration in the formation allowed for excellent preservation of fine microstructures on thesemicrofossils. Among the rich palynomorph assemblage in Lükati, a new species of tiny, spheroidal eukaryoticmicrofossil is recorded: Reticella corrugata gen. et sp. nov. It is characterised by a corrugated and flexible vesicle wallthat is densely perforated by nano-scale pores. Despite its unique morphology, the new species shares diagnosticcharacters with fossil and extant prasinophyte algae. R. corrugata is among the smallest microfossils with typicaleukaryotic morphology (conspicuous wall sculpture) and contributes to the diversity of the size class of smallacritarchs. Size, abundance, inferred prasinophyte affinity and eukaryotic wall sculpture make this new taxon alikely member of the early eukaryotic picoplankton.

  • 11.
    Agić, Heda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Fossil Focus: Acritarchs2016In: Palaeontology Online, Vol. 6, no 11, p. 1-13Article in journal (Other (popular science, discussion, etc.))
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  • 12.
    Agić, Heda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Microfossils of eukaryotic cysts through time: A study of Precambrian-Ordovician organic-walled microbiota2014Licentiate thesis, comprehensive summary (Other academic)
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    microfossils of eukaryotic cysts -licH.A.
  • 13.
    Agić, Heda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the most important events in the history of life is the evolution of the complex, eukaryotic cell. The eukaryotes are complex organisms with membrane-bound intracellular structures, and they include a variety of both single-celled and multicellular organisms: plants, animals, fungi and various protists. The evolutionary origin of this group may be studied by direct evidence of past life: fossils. The oldest traces of eukaryotes have appeared by 2.4 billion years ago (Ga), and have additionally diversified in the period around 1.8 Ga. The Mesoproterozoic Era (1.6-1 Ga) is characterised by the first evidence of the appearance complex unicellular microfossils, as well as innovative morphologies, and the evolution of sexual reproduction and multicellularity. For a better understanding of the early eukaryotic evolution and diversification patterns, a part of this thesis has focused on the microfossil records from various time periods and geographic locations. Examination of microfossil morphology, cell wall microstructure and biochemical properties, reflect their intracellular complexity and function, and allow reconstructions of their life cycle, as well as observing the evolutionary pattern of change from Mesoproterozoic, to Cambrian-Ordovician transition. Several case studies included assemblages deriving from Mesoproterozoic, Neoproterozoic and early Paleozoic time intervals that show disparate morphotypes and innovative features indicative of algal clades. The Mesoproterozoic Ruyang Group in northern China has yielded a diverse microfossil assemblage that provides important clues about the diversification of different eukaryotic groups. Furthermore these microfossils contributed an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga. In another part of this thesis, examination of wall microstructure and chemical properties via Raman spectroscopy has been used to assess the biological affinities of various Neoproterozoic problematic carbonaceous compression fossils. Studies on the early Phanerozoic (c. 545-485 Ma) assemblages from Estonia reconstructed patterns of the early radiations of phytoplankton and its evolutionary innovations. A continuing theme in this thesis has been using a combination of evidence of microfossils’ fine-scale morphology, ecology and chemical properties to determine their function in life, in addition to their systematic position.

    List of papers
    1. Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China
    Open this publication in new window or tab >>Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China
    2015 (English)In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 89, no 1, p. 28-50Article in journal (Refereed) Published
    Abstract [en]

    Light microscope and scanning electron microscope observations on new material of unicellularmicrofossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the MesoproterozoicRuyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellularcomplexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoicmicrofossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties ofresistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgalcysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development ofreproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst)stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates areproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolicallyexpensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these charactersand from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stemgroup of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera andShuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembranesystem and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biotareveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryoticevolution and the development of complex life cycles with sexual reproduction by 1200Ma.

    Place, publisher, year, edition, pages
    Cambridge Journals, 2015
    Keywords
    organic-walled microfossils; early eukaryotes; Mesoproterozoic; Dictyosphaera; Shuiyousphaeridium; algae; evolution; intracellular complexity
    National Category
    Geology
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology; Biology with specialization in Systematics
    Identifiers
    urn:nbn:se:uu:diva-247264 (URN)10.1017/jpa.2014.4 (DOI)000351478500003 ()
    Funder
    Swedish Research Council, 621-2009-4445
    Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2017-12-04Bibliographically approved
    2. Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
    Open this publication in new window or tab >>Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
    2017 (English)In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, p. 101-130Article in journal (Refereed) Published
    Abstract [en]

    Mesoproterozoic Era was an important time for the initial diversification of eukaryotic groups and the appearance of the first complex morphologies. While eukaryotes evolved around 2.4 Ga, the first microfossils with ornamentation and sculpture occur in the 1.8-1.6 Ga successions worldwide. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record a high diversity of such organic-walled microfossils. Recently, the depositional ages of this succession has been constrained to 1.75-1.40 Ga via   zircon U-Pb dating. This dating extends back the time of the first appearance of complex eukaryotic characters (e.g. processes, complex wall structure) in the fossil record. We have conducted a biostratigraphic investigation on of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope studies have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Fossil diversity is high in the upper Baicaoping Formation, declines in the middle and reaches its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota include a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera, Shuiyousphaeridium, and Tappania. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts among modern protists. These microfossils provide an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga.

    Keywords
    Mesoproterozoic, Ruyang Group, organic-walled microfossils, eukaryotic evolution, North China, Dictyosphaera.
    National Category
    Natural Sciences Geology
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology
    Identifiers
    urn:nbn:se:uu:diva-265216 (URN)10.1016/j.precamres.2017.04.042 (DOI)000404697200006 ()
    Projects
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Funder
    Swedish Research Council, 621-2009-4445
    Available from: 2015-10-25 Created: 2015-10-25 Last updated: 2018-02-22Bibliographically approved
    3. Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platforms
    Open this publication in new window or tab >>Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platforms
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Macroscopic, organic-walled fossils preserved as carbonaceous compressions and body fossils are commonly occurring in the Neoproterozoic-Cambrian successions worldwide. Most of these fossils, including studied here Chuaria, Tawuia, and Beltemelliformis, have been accepted as algae, and Sabellidites as an early metazoan. They possess limited characters for biological identification and differ in gross morphology of spherodial vs. tubular millimetre-sized specimens. Consequently, other methods than morphologic observations are needed to elucidate their affinities and, ultimately, phylogeny. Here we present a comparison of the Raman spectrographic signatures and new scanning electron microscope (SEM) observations on different carbonaceous compression and body fossils from the Khajpakh Formation (Siberian Platform), and Nekrasovo Formation (East European Platform), referred to the Tonian-Cryogenian transitional interval (c. 840-700 Ma) and the lowermost Cambrian stage, respectively. Data from the Raman spectroscopy of the walls of non-mineralised organisms reveal their chemical properties, and, in additions to microstructural characters, may be used to resolve the fossils’ phylogenetic affinities. To test the basic recognition of organic matter in studied photosynthetic organisms vs. animals, we have examined algal compression fossils and organically-preserved body-fossil. Differences in the Raman spectroscopic signature between various taxa have been observed. Vibrational absorption bands similar to those characteristic of α-chitin signature have been detected in the organic wall of Sabellidites, consistent with its metazoan identity. Distinct organic matter spectra of the macroalgae Chuaria, Tawuia and Beltanelliformis, and the possible early annelid Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes. Additionally, the recognition of the earliest metazoans among un-diagnostic tubular fossils by biochemical signatures and wall ultrastructure, could provide the minimum age of their origins.

    Keywords
    Neoproterozoic, Cambrian, tubular fossils, organic body fossils, Raman spectroscopy, SEM, East European Platform, Siberian Platform
    National Category
    Natural Sciences Geology
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology
    Identifiers
    urn:nbn:se:uu:diva-265206 (URN)
    Projects
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Funder
    Swedish Research Council, 621-2012-1669
    Available from: 2015-10-25 Created: 2015-10-25 Last updated: 2015-12-04
    4. Ecdysozoan-like sclerites among Ediacaran microfossils
    Open this publication in new window or tab >>Ecdysozoan-like sclerites among Ediacaran microfossils
    2015 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 152, no 6, p. 1145-1148Article in journal (Refereed) Published
    Abstract [en]

    We report the occurrence of organically preserved microfossils from the subsurface Ediacaran strata overlying the East European Platform in Poland, in the form of sclerites and cuticle fragments of larger organisms. They are morphologically similar to those known from Cambrian strata and associated with various metazoan fossils of recognized phyla. The Ediacaran age of the microfossils is evident from the stratigraphic position below the base of the Cambrian System and above the isotopically dated tuff layers at c. 551±4Ma. Within this strata interval, other characteristic Ediacaran microorganisms co-occur such as cyanobacteria, vendotaenids, microalgae, Ceratophyton,Valkyria and macroscopic annelidan Sabellidites. The recent contributions of organic sclerites in revealing the scope of the Cambrian explosion are therefore also potentially extendable back to the Ediacaran Period when animals first appear in the fossil record.

    Place, publisher, year, edition, pages
    Cambridge: Cambridge University Press, 2015
    Keywords
    Ediacaran metazoans; small carbonaceous fossils; Poland; organic preservation; refractory biopolymers
    National Category
    Geology
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology
    Identifiers
    urn:nbn:se:uu:diva-264156 (URN)10.1017/S001675681500045X (DOI)000367730400013 ()
    Funder
    Swedish Research Council, 621-2012-1669, 621-2011-4703
    Available from: 2015-10-06 Created: 2015-10-06 Last updated: 2017-12-01Bibliographically approved
    5. A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton
    Open this publication in new window or tab >>A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton
    2016 (English)In: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 40, no 3, p. 343-356Article in journal (Refereed) Published
    Abstract [en]

    The Proterozoic-Phanerozoic transition records a general trend of decrease in phytoplankton cell size, in contrast tothe earlier and much larger Ediacaran acritarchs. Particularly minute, unornamented but sculptured organic-walledmicrofossils have been recovered from the lower Cambrian Lükati Formation in northern Estonia. The lack of anysignificant thermal alteration in the formation allowed for excellent preservation of fine microstructures on thesemicrofossils. Among the rich palynomorph assemblage in Lükati, a new species of tiny, spheroidal eukaryoticmicrofossil is recorded: Reticella corrugata gen. et sp. nov. It is characterised by a corrugated and flexible vesicle wallthat is densely perforated by nano-scale pores. Despite its unique morphology, the new species shares diagnosticcharacters with fossil and extant prasinophyte algae. R. corrugata is among the smallest microfossils with typicaleukaryotic morphology (conspicuous wall sculpture) and contributes to the diversity of the size class of smallacritarchs. Size, abundance, inferred prasinophyte affinity and eukaryotic wall sculpture make this new taxon alikely member of the early eukaryotic picoplankton.

    Keywords
    Cambrian, Estonia, organic-walled microfossils, picoplankton, prasinophytes, small acritarchs
    National Category
    Geology Ecology
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology
    Identifiers
    urn:nbn:se:uu:diva-265208 (URN)10.1080/01916122.2015.1068879 (DOI)000386047200007 ()
    Projects
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Funder
    Swedish Research Council, 621-2012-1669
    Available from: 2015-10-25 Created: 2015-10-25 Last updated: 2020-01-17Bibliographically approved
    6. Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils
    Open this publication in new window or tab >>Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils
    2016 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, no 2, p. 278-294Article in journal (Refereed) Published
    Abstract [en]

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480 million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Paleozoic Era: novel morphologies appearing through the Cambrian and subsequently diversifying in the Ordovician. Well preserved specimens were extracted following a standard palynological method and studied by light transmitted microscopy. The galeate plexus acritarchs Caldariola, Priscogalea and Stelliferidium have revealed exceptionally preserved morphological elements and a rare structure among both fossil and extant protists – an opening with operculum (lid) in reproductive cysts, in addition to lavish vesicle ornamentation and sculpture. Analogous morphology is observed in the living dasycladalean alga Acetabularia (Chlorophyta), which possesses an intrinsic lid-forming apparatus used during organism’s reproductive stage. Based on the observations on the fossil material and studies on the Acetabularia lid-formation, we propose a model of operculum formation in the galeate plexus microorganisms. Due to strong morphological and ecological similarities between galeate fossils and dasycladalean cysts, and the antiquity of this algal order, galeates may be positioned within green algae, more specifically Dasycladales. Unique morphology of the operculum-bearing microbiota would have required a high degree of intracellular complexity for its development, suggesting that advanced intracellular machinery was present already in the early Paleozoic phytoplankton. Additionally, minute prasinophyte microfossils Reticella corrugata  are reported for the first time in the Upper Cambrian strata. 

    Keywords
    acritarchs, Baltica, cyst-formation, Dasycladales, Estonia, galeate plexus, microfossils, operculum, Ordovician, palaeobiology
    National Category
    Geology Botany
    Research subject
    Earth Science with specialization in Historical Geology and Palaeontology
    Identifiers
    urn:nbn:se:uu:diva-265207 (URN)10.1080/11035897.2015.1116603 (DOI)000379763500001 ()
    Projects
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Funder
    Swedish Research Council, 621-2012-1669Danish National Research Foundation, DNRF53
    Available from: 2015-10-25 Created: 2015-10-25 Last updated: 2017-12-01Bibliographically approved
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  • 14.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Is cyst formation in early eukaryotes a requirement for their preservation in the fossil record?2015In: Abstracts of the Astrobiology Science Conference 2015: Habitability, Habitable Worlds and Life: EARTH’S EARLY BIOSPHERE: LIFE ON AN “ALIEN” PLANET, 2015Conference paper (Refereed)
    Abstract [en]

    Most of the Archaean-Proterozoic fossil record consists of non-biomineralizing microorganisms or their signatures. Body fossils of bacteria and early eukaryotes are preserved in siliciclastics, shales and carbonates, and are usually studied by preparation of thin sections or extraction from the rock matrix via acid maceration.The first eukaryotic organic-walled microfossils (OWM) appear at least by 1.8 Ga and undergo morphological diversification and evolutionary radiation in the Mesoproterozoic. There are no preserved eukaryotic-grade microfossils except OWM until the onset of biomineralization much later in the Neoproterozoic, evident in the record of testate amoebae (VSM) and microfossils with scaly elements.OWM are a less conspicuous component of the fos-sil record than taxa with skeletal or shelly elements. Organic matter decays quickly upon death of the organism, due to autolytic enzymes or degradation via het-erotrophy. However, species producing vegetative cells, resting cysts, zygotes, or spores, show considerable resistance to autolysis. Case studies on extractable carbonaceous OWM indicate they are preserved due to complex refractory molecules in the structure of their sturdy vesicle walls. Living analogues across protistan clades utilise such sporopollenin-like compounds for the cyst wall construction during reproductive phase. Algaenan-containing trilaminar sheath structure (TLS) is secreted during aplanospore formation in extant chlorophyte alga Haematococcus. TLS has also been documented in Leiosphaeridia acritarchs from the Cambrian Lükati Formation in Estonia. Leiosphaeridia is a long ranging morphotype, dating as far back as 1.8 Ga. Presence of TLS in these fossils suggests their function as reproductive cyst. Dictyosphaera-Shuiyousphaeridium plexus from the Mesoproterozoic Ruyang Group, China, also exhibits cyst-like morphology and unique elements of wall reinforcement: internally secreted organic platelets.In addition to these early OWM, many Meso-Neoproterozoic taxa such as Tappania, Trachyhystrychosphaera and Kildinella contain cyst-like characters: 1) reproductive openings, 2) ornamentation, 3) occa-sionally preserved internal bodies and 4) acetolysis-resistant vesicle walls – properties observed among extant encysting protists.Ornamented (process-bearing) microfossils in par-ticular bear strong similarities with zygotes of living unicellular algae. Property of acetolysis-resistant vesicle is a result of sporopollenin-like macromolecules in the wall, synthesized most commonly by the autotrophic eukaryotes. Presence of such recalcitrant organic walls requires significant metabolic investment by the microorganism, which suggests a protective and/or reproductive function. This also allows for easier, and more detailed preservation in the rock record.One of the concerns arising from the studies on the early eukaryotic fossils is the bias towards encysting organisms. The eventual search for the fossil record on other planetary bodies could face the same challenges as the Precambrian palaeobiology: fossilisation and eventual detection might be problematic for any unicellular eukaryotic-grade organisms if they have not evolved reproduction via encystment, or cyst formation as means of coping with adverse environmental conditions.

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  • 15.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Raman spectra analysis and comparison of Neoproterozoic organic-walled mesofossils2012In: The 2012 Fermor Meeting of the Geological Society: The Neoproterozoic Era: Evolution, Glaciation, Oxygenation / [ed] Fairchild I., Condon D., Lenton T., Shields-Zhou G., Brasier M.D., London, 2012, Vol. 1, p. 86-Conference paper (Refereed)
    Abstract [en]

    Skeletal material first appears in the rock record in the terminal Ediacaran, leaving most of the Earth’s history only to minute organic fossils. Aside from abundant acritarchs (unicellular organic-walled phytoplankton) present from at least ~2.5 Ga, other Proterozoic organic fossils of complex (eukaryotic) organisms include fungi and macroscopic algae of still debated taxonomy. Often preserved as flattened carbonaceous filaments in several morphologies: (1) rounded, (2) stick-like elongate and (3) branching, these Neoproterozoic fossils, including Chuaria, Morania, Beltanelloides, Vendotaenia, possess limited characters and differ little in gross morphology. As a result, other methods are needed to elucidate their biological affinities and, ultimately, phylogeny.

    Here we present the comparison of the Raman spectra analysis of different macroalgal genera from Yakutia, Siberia, as well as that of a putative polychaete Sabellidites from the East European Platform, dated to the early Cryogenian (840-700 Ma) and lowermost Cambrian respectively.

    Data from the vibrational modes of organic molecules from the wall of unmineralised organisms reveal their chemistry and partially wall ultrastructure, presumably an indication of their relationships. Polyaromatic chain hydrocarbons and n-aliphatic pyrolysates suggest algal affinity for some of the Neoproterozoic organic problematica, yet most of the Raman spectra results are still difficult to fully identify, partially owing to the thermal maturity of the host rocks. However, there are clear differences between various groups, differentiating between parts of a single plexus (cf previous studies of Chuaria-Tawuia suggesting them to be components of a multicellular plant) and elements from other taxa. Additionally, the distinct organic matter spectra of Chuaria and Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes.

    As they are usually shallow-water and dependant on sunlight, the record of sturdy photosynthetic macroorganisms in the  Neoproterozoic strengthens the evidence that limits the extent of the harsh environmental conditions during the Cryogenian period, at least during the Kaigas and Sturtian glaciations.

  • 16.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platformsManuscript (preprint) (Other academic)
    Abstract [en]

    Macroscopic, organic-walled fossils preserved as carbonaceous compressions and body fossils are commonly occurring in the Neoproterozoic-Cambrian successions worldwide. Most of these fossils, including studied here Chuaria, Tawuia, and Beltemelliformis, have been accepted as algae, and Sabellidites as an early metazoan. They possess limited characters for biological identification and differ in gross morphology of spherodial vs. tubular millimetre-sized specimens. Consequently, other methods than morphologic observations are needed to elucidate their affinities and, ultimately, phylogeny. Here we present a comparison of the Raman spectrographic signatures and new scanning electron microscope (SEM) observations on different carbonaceous compression and body fossils from the Khajpakh Formation (Siberian Platform), and Nekrasovo Formation (East European Platform), referred to the Tonian-Cryogenian transitional interval (c. 840-700 Ma) and the lowermost Cambrian stage, respectively. Data from the Raman spectroscopy of the walls of non-mineralised organisms reveal their chemical properties, and, in additions to microstructural characters, may be used to resolve the fossils’ phylogenetic affinities. To test the basic recognition of organic matter in studied photosynthetic organisms vs. animals, we have examined algal compression fossils and organically-preserved body-fossil. Differences in the Raman spectroscopic signature between various taxa have been observed. Vibrational absorption bands similar to those characteristic of α-chitin signature have been detected in the organic wall of Sabellidites, consistent with its metazoan identity. Distinct organic matter spectra of the macroalgae Chuaria, Tawuia and Beltanelliformis, and the possible early annelid Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes. Additionally, the recognition of the earliest metazoans among un-diagnostic tubular fossils by biochemical signatures and wall ultrastructure, could provide the minimum age of their origins.

  • 17.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Canfield, Donald
    University of Southern Denmark.
    Cyst and operculum formation in Cambrian-Ordovician galeate acritarchs from Estonia: implications for the algal phylogeny and blooms in the early Paleozoic2014In: 4th International Palaeontological Congress Abstract Volume: The history of life: a view from the Southern Hemisphere, 2014, p. 913-Conference paper (Other academic)
    Abstract [en]

    Unicellular organic-walled microfossils have been recovered from the Cambrian Lükati Formation and the Tremadocian Varangu Formation exposed in northern Estonia. Due to a combination of main morphological and biochemical characters, mainly a) excystment opening, b) processes, c) acetolysis-  resistant vesicle wall, microfossils have been interpreted as reproductive cysts of green algae. Both microfossil assemblages reflect the evolutionary patterns though the early Palaeozoic: from the Cambrian radiation of morphologically innovative taxa to increase in diversity and more disparate Ordovician forms. Combined light transmitted and scanning electron microscopy on the Middle Cambrian to Tremadocian galeate plexus acritarchs CaldariolaPriscogalea and Stelliferidium, revealed exceptionally preserved morphological elements and rare structure among fossil and extant microbiota – an opening with operculum (lid) in reproductive cyst, in addition to lavish vesicle ornamentation and sculpture. Operculum formation model is reconstructed from fossils at different stages of operculum position and attachment. Comparative morphology shows strong similarity of galeates to the reproductive cysts of the extant algae of Dasycladales (Chlorophyta), where the lid covering the cyst opening is determined by an intrinsic lid-forming apparatus during the organism’s reproductive stage. Opercula in Cambro-Ordovician galeate acritarchs and Dasycladales may be considered a homologous character. Unique morphology of the operculum-bearing microbiota would have required a degree of intracellular sophistication for its development, suggesting advanced intracellular machinery present already in the early Palaeozoic phytoplankton. Additionally, a new species of minute, sphaeromorphic and aggregated eukaryotic microfossils is recorded. It possesses a vesicle wall with corrugated sculpture and perforated by nano-scale pores. These minute early Cambrian microfossils have diagnostic characters of prasinophyte algae.

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    fulltext
  • 18.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Canfield, Donald
    University of Southern Denmark .
    Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils2016In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, no 2, p. 278-294Article in journal (Refereed)
    Abstract [en]

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480 million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Paleozoic Era: novel morphologies appearing through the Cambrian and subsequently diversifying in the Ordovician. Well preserved specimens were extracted following a standard palynological method and studied by light transmitted microscopy. The galeate plexus acritarchs Caldariola, Priscogalea and Stelliferidium have revealed exceptionally preserved morphological elements and a rare structure among both fossil and extant protists – an opening with operculum (lid) in reproductive cysts, in addition to lavish vesicle ornamentation and sculpture. Analogous morphology is observed in the living dasycladalean alga Acetabularia (Chlorophyta), which possesses an intrinsic lid-forming apparatus used during organism’s reproductive stage. Based on the observations on the fossil material and studies on the Acetabularia lid-formation, we propose a model of operculum formation in the galeate plexus microorganisms. Due to strong morphological and ecological similarities between galeate fossils and dasycladalean cysts, and the antiquity of this algal order, galeates may be positioned within green algae, more specifically Dasycladales. Unique morphology of the operculum-bearing microbiota would have required a high degree of intracellular complexity for its development, suggesting that advanced intracellular machinery was present already in the early Paleozoic phytoplankton. Additionally, minute prasinophyte microfossils Reticella corrugata  are reported for the first time in the Upper Cambrian strata. 

  • 19.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China2015In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 89, no 1, p. 28-50Article in journal (Refereed)
    Abstract [en]

    Light microscope and scanning electron microscope observations on new material of unicellularmicrofossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the MesoproterozoicRuyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellularcomplexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoicmicrofossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties ofresistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgalcysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development ofreproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst)stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates areproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolicallyexpensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these charactersand from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stemgroup of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera andShuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembranesystem and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biotareveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryoticevolution and the development of complex life cycles with sexual reproduction by 1200Ma.

  • 20.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution2017In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, p. 101-130Article in journal (Refereed)
    Abstract [en]

    Mesoproterozoic Era was an important time for the initial diversification of eukaryotic groups and the appearance of the first complex morphologies. While eukaryotes evolved around 2.4 Ga, the first microfossils with ornamentation and sculpture occur in the 1.8-1.6 Ga successions worldwide. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record a high diversity of such organic-walled microfossils. Recently, the depositional ages of this succession has been constrained to 1.75-1.40 Ga via   zircon U-Pb dating. This dating extends back the time of the first appearance of complex eukaryotic characters (e.g. processes, complex wall structure) in the fossil record. We have conducted a biostratigraphic investigation on of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope studies have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Fossil diversity is high in the upper Baicaoping Formation, declines in the middle and reaches its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota include a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera, Shuiyousphaeridium, and Tappania. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts among modern protists. These microfossils provide an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga.

  • 21.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moczydłowska, Małgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Morphology of the Proterozoic eukaryotic microfossils as a reflection of their intracellular complexity2014In: 4th International Palaeontological Congress Abstract Volume: The history of life: a view fom the southern hemisphere / [ed] Esperanza CERDEÑO, 2014, p. 256-Conference paper (Refereed)
    Abstract [en]

    Mesoproterozoic is a time of increasing diversity of microscopic life and appearance of intricate new cell morphologies. First eukaryotes may have evolved around 2.4 Ga, but the first microbiota with intricate sculpture and ornamentation are found in the younger, 1.8.-1.6 Ga successions worldwide. Such microfossils were uncovered from the Ruyang Formation in Shanxi, China and Roper Group, Northern Territories, Australia, dating back to 1.6-1.0 Ga ago. Some of these unicellular organic-walled fossils share characters with Ediacaran and Phanerozoic fossils, as well as extant green microalgae. Key characters among some Precambrian acritarchs are acetolysis-resistant vesicle with multi-layered walls; vesicle ornamentation by diverse processes that are produced during cyst formation; and excystment openings for the release of gametes or daughter-cells. Combination of these morphological elements, also present in extant phytoplankton, reflects the fossils’ protective function as reproductive cysts, indicating that complex life cycles and reproduction were well under way in Mesoproterozoic. Several case studies of microfossil morphology likely induced by intrinsic eukaryotic mechanisms are presented.

    Distinctive vesicle wall composed of the primary layer reinforced by polygonal platelets in Mesoproterozoic taxa Dictyosphaera and Shuiyouisphaeridium, as well as the sophisticated vesicle-wall patterning on the fossil sphaeromorphs Valeria and younger Cerebrosphaera would have required a certain degree of complexity for their formation, as observed in the present day analogues among eukaryotic protists. This suggests the activity of the key eukaryotic organelles and cellular mechanisms and signalling for the cyst formation. Considering that Golgi apparatus and the endoplasmatic reticulum are the organelles regulating eukaryotic secretory pathway and synthesis of biopolymers used in cell-wall construction, they would have been required for the complex morphology observed in these Precambrian taxa. Therefore, the presence of GA and ER in the eukaryotic cell is inferred at the minimum age of 1.6-1.4 Ga. Similarly, morphology of acritarchs of the Cambrian galeate plexus, namely openings with opercula, is likely induced by the activity of the LFA organelle (lid-forming apparatus) as in the extant dasycladalean alga Acetabularia.

    Additionally, several new morphotypes from the Ruyang Formation are presented. These unicellular fossils bear a velutinous outer membrane surrounding an internal sphere, which suggests a protective function of a reproductive or a resting cyst.

    Cyst-like morphology varies in disparity, but its key features are consistent through Mesoproterozoic, Neoproterozoic and early Palaeozoic.

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  • 22.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Ward, L.
    Juarez Rivera, M.
    Kerrigan, Z.
    Petryshyn, V.A.
    Corsetti, F.A.
    Tripati, A.
    Lateral growth of Late Pleistocene stromatolites from Walker Lake (Nevada) and proxy constraints on environmental change2014In: 2014 GSA Annual Meeting in Vancouver, 2014Conference paper (Refereed)
    Abstract [en]

    Walker Lake, a terminal sodium bicarbonate lake in Western Nevada (Great Basin, USA) contains numerous carbonate structures, including stromatolites. The lake is a remnant of the larger Pleistocene Lake Lahontan system that has been isolated for the last ~12 ka. Stromatolites of unique macroscale morphology were collected at the ancient Lahontan shoreline during the 2014 International Geobiology Course.

    Initial observations of a stromatolite bed revealed a bowl-shaped carbonate framework composed of stacked, weakly laminated, vertical and horizontal petal-like structures with copious pore space. One laterally-oriented petal was taken off of the main structure and studied. Petrographical observations exhibit two types of alternating microfabrics and three transitions in microfabric. Both sparry crystal fans of calcite, and convex layers of fine micrite with occasional trapped crystals and fossils, were observed.

    Calibrated 14C ages (IntCal13) for the proximal and the distal end of the stromatolite are 35,540 YBP and 33,580 YBP, respectively. Clumped isotope (D47)-based estimates of temperature steadily increase throughout most of this interval, from the beginning of accretion, to the middle of the structure. By the distal end, values are at their peak, and at the tip temperatures decrease again. D47-temperatures correspond to microfabric, with textural changes associated with evidence for climatic fluctuations.

    We suggest the stromatolite formation may have been initiated during warmer intervals, induced by the chemical precipitation of calcite fans which served as a substrate for a biofilm growth. Microbial activity trapped the fine sediment and formed micrite. Colder conditions propagated fan precipitation. Microfabric alternation throughout the stromatolite records environmental change in the span of ca. 2000 years of Lake Lahontan history, likely in response to lake level fluctuations.

  • 23.
    Agić, Heda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Ward, Lewis
    California Institute of Technology.
    Juarez Rivera, Marisol
    University of California-Davis.
    Kerrigan, Zak
    University of Rhode Island.
    Petryshyn, Victoria A.
    University of California, Los Angeles.
    Corsetti, Frank A.
    University of Southern California.
    Tripati, Aradhna
    University of California, Los Angeles.
    Lateral growth of Late Pleistocene stromatolites from Walker Lake (Nevada) and proxy constrains on environmental change2014In: Geological Society of America Abstracts with Programs, Geological Society of America , 2014, p. 300-4-Conference paper (Other academic)
    Abstract [en]

    Walker Lake, a terminal sodium bicarbonate lake in Western Nevada (Great Basin, USA) contains numerous carbonate structures, including stromatolites. The lake is a remnant of the larger Pleistocene Lake Lahontan system that has been isolated for the last ~12 ka. Stromatolites of unique macroscale morphology were collected at the ancient Lahontan shoreline during the 2014 International Geobiology Course.

    Initial observations of a stromatolite bed revealed a bowl-shaped carbonate framework composed of stacked, weakly laminated, vertical and horizontal petal-like structures with copious pore space. One laterally-oriented petal was taken off of the main structure and studied. Petrographical observations exhibit two types of alternating microfabrics and three transitions in microfabric. Both sparry crystal fans of calcite, and convex layers of fine micrite with occasional trapped crystals and fossils, were observed.

    Calibrated 14C ages (IntCal13) for the proximal and the distal end of the stromatolite are 35,540 YBP and 33,580 YBP, respectively. Clumped isotope (D47)-based estimates of temperature steadily increase throughout most of this interval, from the beginning of accretion, to the middle of the structure. By the distal end, values are at their peak, and at the tip temperatures decrease again. D47-temperatures correspond to microfabric, with textural changes associated with evidence for climatic fluctuations.

    We suggest the stromatolite formation may have been initiated during warmer intervals, induced by the chemical precipitation of calcite fans which served as a substrate for a biofilm growth. Microbial activity trapped the fine sediment and formed micrite. Colder conditions propagated fan precipitation. Microfabric alternation throughout the stromatolite records environmental change in the span of ca. 2000 years of Lake Lahontan history, likely in response to lake level fluctuations.

  • 24. Ahl, Martin
    et al.
    Bergman, Stefan
    Bergström, Ulf
    Eliasson, Thomas
    Ripa, Magnus
    Weihed, Pär
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Geochemical classification of plutonic rocks in central and northern Sweden2001Report (Other academic)
  • 25.
    Ahlberg, K., Almgren, E., Wright, H.E., Ito, E.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Holocene stable-isotope stratigraphy at Lough Gur, County Limerick, Western Ireland2001In: The Holocene, Vol. 11, no 3, p. 375-380Article in journal (Refereed)
  • 26.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Follow the footprints and mind the gaps: a new look at the origin of tetrapods2019In: Earth and environmental science transactions of the Royal Society of Edinburgh, ISSN 1755-6910, E-ISSN 1755-6929, Vol. 109, no 1-2, p. 115-137Article in journal (Refereed)
    Abstract [en]

    The hypothesis that tetrapods evolved from elpistostegids during the Frasnian, in a predominantly aquatic context, has been challenged by the discovery of Middle Devonian tetrapod trackways predating the earliest body fossils of both elpistostegids and tetrapods. Here I present a new hypothesis based on an overview of the trace fossil and body fossil evidence. The trace fossils demonstrate that tetrapods were capable of performing subaerial lateral sequence walks before the end of the Middle Devonian. The derived morphological characters of elpistostegids and Devonian tetrapods are related to substrate locomotion, weight support and aerial vision, and thus to terrestrial competence, but the retention of lateral-line canals, gills and fin rays shows that they remained closely tied to the water. Elpistostegids and tetrapods both evolved no later than the beginning of the Middle Devonian. The earliest tetrapod records come from inland river basins, sabkha plains and ephemeral coastal lakes that preserve few, if any, body fossils; contemporary elpistostegids occur in deltas and the lower reaches of permanent rivers where body fossils are preserved. During the Frasnian, elpistostegids disappear and these riverine-deltaic environments are colonised by tetrapods. This replacement has, in the past, been misinterpreted as the origin of tetrapods.

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  • 27.
    Ahlberg, Per. E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Blom, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology, Palaeontology group.
    Clack, J. A.
    The axial skeleton of the Devonian Tetrapod Ichthyostega2003In: The Gross Symposium 2. Advances in Palaeoichthyology. Riga, Latvia., 2003, p. 7-8Conference paper (Refereed)
  • 28.
    Ahlberg, Per E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Brazeau, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Clément, Gaël
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Snitting, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    The virtual Eusthenopteron: inside the head of a Devonian lobe-fin with CT.2005Conference paper (Refereed)
  • 29.
    Ahlberg, Per E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Brazeau, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Clément, Gaël
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Snitting, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    The virtual Eusthenopteron: inside the head of a Devonian lobe-fin with CT. In A. Ivanov and G. Young (eds.), Middle Palaeozoic Vertebrates from Laurussia: Relationships with Siberia, Kazakhstan, Asia and Gondwana. Ichthyolith Issues Special Publication 9:3–4.2005Other (Other academic)
  • 30.
    Ahlberg, Per E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Clack, J. A.
    Blom, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology, Palaeontology group.
    The axial skeleton of the Devonian Tetrapod Ichthyostega.2003In: 51st symposium of vertebrate palaeontology and comparative anatomy, Oxford University Museum of Natural History, Oxford, 2003, p. 3-Conference paper (Refereed)
  • 31.
    Ahlberg, Per E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Clack, Jennifer A.
    Palaeontology: A firm step from water to land2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 440, no 7085, p. 747-749Article in journal (Refereed)
  • 32.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Gessner, Klaus
    Geol Survey Western Australia, 100 Plain St, East Perth, WA 6004, Australia.
    Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia2016In: Tectonophysics, Vol. 689, p. 56-66Article in journal (Refereed)
    Abstract [en]

    The Murchison domain forms the northwest part of the Youanmi Terrane, a tectonic unit within the Neoarchean Yilgarn Craton in Western Australia. In the Cue-Weld Range area the Murchison domain has experienced a complex magmatic and deformation history that resulted in a transposed array of greenstone belts that host significant iron, gold, and base metal deposits. In this study, we interpret the upper 2 s (about 6 km) of a deep crustal seismic profile TOGA-YU1, near the town of Cue, and correlate rock units and structures in outcrop with corresponding reflections. We performed 3D constant velocity ray-tracing and calculate the corresponding travel times for the reflectionsfor time domain pre-stack and post-stack seismic data. This allows us to link shallow reflections with mafic volcanic rocks of the Glen Group and basaltic rocks of the Polelle Group in outcrop. Based on our interpretation and published geological maps and data, we propose a model in which the local stratigraphy represents a refolded thrust system. To test our hypothesis, we applied 2D acoustic finite difference forward modeling. The corresponding synthetic data were processed in the same way as the acquired data. Comparisons between the acquired and the synthetic data show that the model is consistent with observations. We propose a new model for the subsurface of the Cue-Weld Range area and argue that some of the lithologies in the area are repeated structurally at different levels. Our approach highlights the benefit of imaging and modeling of deep seismic transects to resolve local structural complexity in Archean granite-greenstone terrains.

  • 33.
    Ahmed, Engy
    et al.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Sci Life Lab, Tomtebodavagen 23A, SE-17165 Solna, Sweden..
    Parducci, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Unneberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Ågren, Rasmus
    Chalmers Univ Technol, Dept Chem & Biol Engn, Sci Life Lab, SE-41296 Gothenburg, Sweden..
    Schenk, Frederik
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Rattray, Jayne E.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Univ Calgary, Biol Sci, 2500 Univ Dr NW, Calgary, AB, Canada..
    Han, Lu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics. Jilin Univ, Coll Life Sci, Ancient DNA Lab, Changchun, Jilin, Peoples R China..
    Muschitiello, Francesco
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Columbia Univ, Lamont Doherty Earth Observ, 61 Route 9NW, Palisades, NY USA..
    Pedersen, Mikkel W.
    Univ Cambridge, Dept Zool, Downing St, Cambridge CB2 3EJ, England..
    Smittenberg, Rienk H.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Yamoah, Kweku Afrifa
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Slotte, Tanja
    Stockholm Univ, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden.;Sci Life Lab, Tomtebodavagen 23A, SE-17165 Solna, Sweden..
    Wohlfarth, Barbara
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Archaeal community changes in Lateglacial lake sediments: Evidence from ancient DNA2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 181, p. 19-29Article in journal (Refereed)
    Abstract [en]

    The Lateglacial/early Holocene sediments from the ancient lake at Hasseldala Port, southern Sweden provide an important archive for the environmental and climatic shifts at the end of the last ice age and the transition into the present Interglacial. The existing multi-proxy data set highlights the complex interplay of physical and ecological changes in response to climatic shifts and lake status changes. Yet, it remains unclear how microorganisms, such as Archaea, which do not leave microscopic features in the sedimentary record, were affected by these climatic shifts. Here we present the metagenomic data set of Hasseldala Port with a special focus on the abundance and biodiversity of Archaea. This allows reconstructing for the first time the temporal succession of major Archaea groups between 13.9 and 10.8 ka BP by using ancient environmental DNA metagenomics and fossil archaeal cell membrane lipids. We then evaluate to which extent these findings reflect physical changes of the lake system, due to changes in lake-water summer temperature and seasonal lake-ice cover. We show that variations in archaeal composition and diversity were related to a variety of factors (e.g., changes in lake water temperature, duration of lake ice cover, rapid sediment infilling), which influenced bottom water conditions and the sediment-water interface. Methanogenic Archaea dominated during the Allerod and Younger Dryas pollen zones, when the ancient lake was likely stratified and anoxic for large parts of the year. The increase in archaeal diversity at the Younger Dryas/Holocene transition is explained by sediment infilling and formation of a mire/peatbog. (C) 2017 Elsevier Ltd. All rights reserved.

  • 34.
    Alakangas, Lena
    et al.
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Bark, Glenn
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Ericsson, Magnus
    Luleå tekniska universitet, Samhällsvetenskap.
    Martinsson, Olof
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Söderholm, Patrik
    Luleå tekniska universitet, Samhällsvetenskap.
    Wanhainen, Christina
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Norrbottens malm- och mineralresurs och dess potentiella betydelse för innovation, samhälle och miljö2014Report (Other academic)
    Abstract [sv]

    Gruvindustrins betydelse för samhällsutveckling och infrastruktur i Sverige och inte minst i Norrbottens län är mycket stor. De geologiska förutsättningarna att hitta nya brytvärda förekomster i Norrbotten är goda. Länet är tillsammans med Västerbotten en av Europas viktigaste regioner för utvinning av metaller. Det syns också i den nyligen framtagna regionala mineralstrategin för Norrbotten och Västerbotten. Visionen för den regionala mineralstrategin: ”Genom långsiktigt hållbart nyttjande av Norrbottens och Västerbottens läns mineralresurser har ytterligare tillväxt skapats i regionen och hela Sverige. Vi har utvecklat och stärkt vår ställning som ledande gruv- och mineralnation.”Eftersom framtidspotentialen för gruvnäringen är mycket god men okunnigheten hos både allmänhet och beslutsfattare om näringens betydelse för innovation och samhällsutveckling är stor, kopplat med en utbredd oro för miljöpåverkan, måste dessa viktiga framtidsfrågor belysas. Med finansiering från Länsstyrelsen i Norrbotten bedrevs därför under första hälften av 2014 en förstudie som syftade till att sammanfatta kunskapsläget om framtidens gruvindustri i Norrbotten. Resultaten av förstudien redovisas i den här rapporten. En viktig slutsats är att det under nästa strukturfondsperiod (med start 2015) behövs ett framtidsinriktat forskningsprogram för att belysa de möjligheter som finns. Denna förstudie utgör grund för en kommande ansökan till strukturfonderna. Kompetensen som finns vid Luleå tekniska universitet, Sveriges centrum för gruvrelaterad forskning och utbildning, bör användas för att studera troliga framtidsmöjligheter och hur de ska kunna användas för att få en så positiv utveckling som möjligt för länet. Projektet bör innehålla följande tre huvudinriktningar, som naturligtvis hör ihop:Vilka malm- och mineralresurser finns det potential för i Norrbotten, och vilka kommer sannolikt att exploateras i framtiden?Vad kommer den exploateringen att ha för betydelse för innovation och samhällsutveckling?Vad kommer den exploateringen att få för miljöeffekter och hur ska man göra för att minska miljöbelastningen?En annan slutsats är att nedlagda gruvområden inte måste ses som förstörd natur. Betydande mervärden som gruvturism skulle kunna skapas om vilja, kreativitet och beslutsamhet finns. Detta är ett givet utvecklingsområde där småföretag och entreprenörer kan göra stor insats om de politiska och myndighetsmässiga förutsättningarna finns. Dessa aspekter skulle också kunna belysas i det föreslagna forskningsprogrammet eller i ett eget projekt.

  • 35.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Possnert, G
    A high-resolution Be-10 profile from deep sea sediment covering the last 70 ka: Indication for globally synchronized environmental events1998In: QUATERNARY SCIENCE REVIEWS, ISSN 0277-3791, Vol. 17, no 11, p. 1023-1032Article in journal (Refereed)
    Abstract [en]

    We present a high-resolution Be-10 profile from deep sea sediments (sampled from Hole 502B in the Caribbean sea) that strongly resembles the 10Be record in ice core profiles, particularly the Vostok core from Antarctica. This high-resolution profile revea

  • 36.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Possnert, G
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Jonfysik.
    The Be-10 marine record of the last 3.5 Ma2000In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, ISSN 0168-583X, Vol. 172, p. 513-517Article in journal (Refereed)
    Abstract [en]

    We present in this study a Be-10 profile from a deep-sea sediment section extending to 3.5 Ma. The Be-10 concentration ranges at 2-14 x 10(8) atoms/g and shows a clear decay trend. The flux of Be-10 ranges at 1-5 x 10(6) atoms/cm(2) y and averages at appr

  • 37.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Possnert, G
    Johnsen, SJ
    Clausen, HB
    Isaksson, E
    Karlen, W
    Hansson, M
    Sixty year Be-10 record from Greenland and Antarctica1998In: PROCEEDINGS OF THE INDIAN ACADEMY OF SCIENCES-EARTH AND PLANETARY SCIENCES, ISSN 0253-4126, Vol. 107, no 2, p. 139-147Article in journal (Refereed)
    Abstract [en]

    We report in this study the distribution of Be-10 in the top 40 m of the Renland ice core (East Greenland) and in a 30 m long core from DML (Dronning Maud Land, Antarctica) for the period 1931-1988. The two sites show differences in Be-10 content, the Ant

  • 38.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Possnert, G
    Technology, Department of Materials Science.
    Peck, J
    King, J
    Colman, S
    Linking the Be-10 continental record of Lake Baikal to marine and ice archives of the last 50 ka: Implication for the global dust-aerosol input1999In: GEOPHYSICAL RESEARCH LETTERS, ISSN 0094-8276, Vol. 26, no 18, p. 2885-2888Article in journal (Refereed)
    Abstract [en]

    We present here a Be-10 profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the approximate to 40 ka Be-10 enhancement and a pattern that strongly marches those from the marine and

  • 39.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Possnert, G
    Scherer, R
    Shi, Ning
    Backman, J
    Boström, K
    Trace-element and major-element stratigraphy in quaternary sediments from the Arctic Ocean and implications for glacial termination2000In: JOURNAL OF SEDIMENTARY RESEARCH, ISSN 1073-130X, Vol. 70, no 5, p. 1095-1106Article in journal (Refereed)
    Abstract [en]

    The distribution patterns of major and trace elements in sediment cores from the Arctic Ocean, specifically the Yermak Plateau and the Nansen Basin, were evaluated as climate and environmental proxy records of the last 350 ka. The sediments are carbonate

  • 40.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. IONPHYSICS /QUATERNARY GEOLOGY.
    Possnert, G
    Technology, Department of Materials Science.
    Vintersved, I
    Atmospheric interactions at northern high latitudes from weekly Be-isotopes in surface air2001In: APPLIED RADIATION AND ISOTOPES, ISSN 0969-8043, Vol. 54, no 2, p. 345-353Article in journal (Refereed)
    Abstract [en]

    We present weekly Be-7 (from 1972 to 1995), and weekly/seasonal Be-10 (for 1994) data in surface air from ground level stations in Sweden with a coverage of most of the northern high latitudes (56 degrees -68 degrees N). Our Be data are regionally represe

  • 41.
    Aldahan, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Ye, HP
    Possnert, G
    Distribution of beryllium between solution and minerals (biotite and albite) under atmospheric conditions and variable pH1999In: CHEMICAL GEOLOGY, ISSN 0009-2541, Vol. 156, no 1-4, p. 209-229Article in journal (Refereed)
    Abstract [en]

    Biotite and albite grains having a size range from 20 to 124 mu m were suspended in Be-bearing solutions at pH 2 to 9 for periods of 30 min to 20 days. The amount of Be sorbed onto biotite is up to 40 times higher than onto albite under the same condition

  • 42.
    Aldahan, AA
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Koeberl, C
    Possnert, G
    Schultz, P
    Be-10 and chemistry of impactites and target materials from the Rio Cuarto crater field, Argentina: Evidence for surficial cratering and melting1997In: GFF, ISSN 1103-5897, Vol. 119, p. 67-72Article in journal (Refereed)
    Abstract [en]

    We report in this study on the distribution of the cosmogenic isotope Be-10 and major and trace elements in impactites (clast-rich melt and glasses) and target materials (soil and loess) from the Rio Cuarto crater field in the Pampas of Argentina. The Be-

  • 43.
    Aldahan, AA
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Ning, S
    Possnert, G
    Backman, J
    Bostrom, K
    Be-10 records from sediments of the Arctic Ocean covering the past 350 ka1997In: MARINE GEOLOGY, ISSN 0025-3227, Vol. 144, no 1-3, p. 147-162Article in journal (Refereed)
    Abstract [en]

    Records of Be-10, Be-9, mineralogy and grain size were obtained from two cores collected by the Polarstern Expedition 1991 in the southern Nansen Basin (Core 2213-6) and the Yermak Plateau (Core 2208-2). The accumulation of sediments examined started from

  • 44.
    Aldahan, Ala
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Geology.
    Mineral diagenesis and petrology of the Dala Sandstone, central Sweden1985Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The Dala Sandstone, of Proterozoic age, is the most extensive sedimentary unit in central Sweden. The rocks are quartz sandstones, lithic sandstones, feldspathic sandstones, arkoses and greywackes with intercalations of shales and siltstones less than 1 m thick. The Öje Basalt divides the sedimentary sequence into two parts. Dolerite dikes and sills of various compositions cut the sedimentary sequence, and in some parts the basalt. The clastic sediments were deposited in a dominantly continental environment. The detrital components of the sandstones are mainly quartz, feldspar and rock fragments. The most common diagenetic minerals are quartz, illite, chlorite, hematite, titanium minerals, calcite and feldspar. Diagenetic illite and chlorite were formed by alteration of detrital feldspars and biotite by authigenesis, and by aggradation crystallization of the fine-crystalline interstitial clay minerals. The sources of iron and titanium for hematite and titanium minerals, respectively, are mainly detrital biotite and ilmenite. The origin of authigenic quartz is mainly the silica produced from alteration of detrital grains, pressure solution of quartz, and replacement of detrital grains by calcite. Calcite and epidote are common as cement in sandstones close to dolerite. The diagenetic chlorite and most of the illite are Fe-rich and generally well crystallized. Their chemical composition and the crystallinity index of illite, as well as the general absence of diagenetic mixed-layer clay minerals (e.g. illite—smectite) and kaolinite, suggest their formation in the temperature range between 150 and 200°C and at maximum pressure of 1.5 kb.

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  • 45.
    Alessandrini, Cameron
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Radiogenic Dating and Microstructure Analysis of Shear Zones Found Within the Seve Nappe Complex in the Åre Region, Jämtland, Scandinavian Caledonides2017Independent thesis Advanced level (degree of Master (Two Years)), 180 HE creditsStudent thesis
    Abstract [en]

    The North Atlantic Caledonides are a continent-continent collision type orogeny found in WesternScandinavia, Svalbard, Greenland and the British Isles. They are thought to have formed as a result of a complex history consisting of repeated ocean opening and closure. The tectonostratigraphy of the Scandinavian Caledonides consists of four allochthons that overlay the crystalline, autochthonous basement. The allochthons are thought to have been transported hundreds of kilometers eastward during the Scandian collision.To investigate the complex history of the Scandinavian Caledonides, a scientific drilling initiative called the Collisional Orogeny in the Scandinavian Caledonides (COSC) project began in 2014. The first phase of the project was to drill a borehole to approximately 2500m depth, to sample a thick section of the Lower Seve Nappe of the Middle Allochthon, as well as the underlying thrust zone.The current hypothesis is that the Middle Seve Nappe has been juxtaposed with the Lower Seve Nappe while still in the subduction channel. Both Seve nappes were emplaced onto the underlying units somewhat later. To test this hypothesis, Rb-Sr dating and Ar-Ar dating has been conducted on white and dark mica found in samples taken from the shear zones. Rb-Sr dating yielded an age of 413 ± 12 Ma and Ar-Ar dating yielded an average age of 424.1± 2.9 Ma. Since the Rb-Sr and Ar-Ar ages overlap, it is interpreted that the crystallization age of the samples is recorded in both cases. Likely, the rocks cooled rather quickly, resulting in a negligible difference in Rb-Sr and Ar-Ar ages. Comparing these results to previous age dating work completed in the same area illustrate a complex subduction/exhumation history. At c. 455 Ma, the Middle and Lower Seve nappes were subducted beneath an island arc and peak pressure metamorphic conditions were reached. Shortly afterwards,exhumation of the subducted sheet began, as a result of the buoyancy of the subducted crust, as well as tectonic under pressure caused by wedge extraction. At c. 424 Ma, the Middle Seve was juxtaposed over the Lower Seve while still in the subduction channel, and at c. 424 - 421.2 Ma both the Middle and Lower Seve nappes were exhumed and transported eastward, where they were thrust above the underlying Särv Nappe and Lower Allochthon, creating the lower shear zone which is the focus of this study. Data from this study will help to establish a coherent model of mid-Palaeozoic mountain building, and provide insight on how this mountain chain, as well as its Himalaya-Tibet analogue have formed.

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  • 46.
    Alfvén, Linda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Structural and Engineering Geological Investigation of Fracture Zones and Their Effect on Tunnel Construction2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project was conducted in connection with the project, Stockholm’s future sewer pipeline, which is a planned sewer pipe that will run through a tunnel from western to southern Stockholm. This tunnel will pass under Lake Mälaren between Eolshäll and Smedslätten, where there are two faults indicated on the geological map, that could affect the tunnelling and create risks during the construction. Geophysical- and water-loss measurements along with core drilling have been carried out in the area. The objectives of this thesis are to create a structural and engineering geological understanding of the passage beneath Lake Mälaren based on drill core mapping, field work, data from previous investi-gations and 2D-models of the tunnel excavation both within and outside the indicated fault zone. The core mapping supports the existence of one fault zone, which is indicated on the geological map supported by water-losses at several places along the drill core as well as core losses. Field work indi-cated the existence of a conjugate fracture sets.The 2D-models present plastic behaviour of the rock in the fault zone as the worst case scenario during excavation with the highest deformation displacement. The excavation procedure and the tunnel form also play a significant role. Since this thesis highlights some significant risks and problems that can occur during tunnelling, its findings may be useful during the tunnel construction.

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  • 47.
    Alfvén, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ignea, Sorin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Characterization of Gas hydrates2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Gas hydrates are naturally occurring crystalline formations consisting of crystal structural “cages” which make up cavities where gas molecules can be trapped. Hydrates are formed under specific pressure and temperature conditions in the ground, which limits their presence to permafrost and deep sea continental margins. The interest for gas hydrates has grown bigger in the past time, mainly because of the potential as a new energy source but also because of the possibility of carbon dioxide (CO2) storage and its potential linkage to different geological hazards. Gas hydrates are still relatively poorly understood with many questions to be answered. Therefore research in this area is important. In our study we have been focusing on characterization of gas hydrate structures and their gas composition. By using the two different analytical methods X-ray powder diffraction (XRD) and gas chromatography. For this study to be successfully carried out we needed access to equipment and expertise which is only to be found in few places on Earth. Our lab work was therefore done at Pontifica Universidade Catolica do Rio Grande do Sul in Porto Alegre Brazil where a research project in gas hydrates is on going. Because of the research projects secrecy we do not know where our gas hydrate samples come from which mean we cannot link our results to any geographic area. The structural analysis shows structure I hydrate which is characterized by the presence of small gas molecules such as hydrocarbons. The results from the gas content validated that it is structure I since large concentrations of methane gas (CH4) and sulphur gas (H2S) were detected. The presence of these gases implies that the formation conditions are in a marine environment at the sulphate-methane transition zone (SMTZ).

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    Characterization of Gas hydrates
  • 48.
    Alhalabi, Wafa A.
    et al.
    Univ Sao Paulo, Dept Biol, FFCLRP, Ave Bandeirantes 3900, BR-14040901 Ribeirao Preto, SP, Brazil..
    Bardet, Nathalie
    CR2P Ctr Rech Paleontol Paris, Museum Natl Hist Nat, CP38,57 Rue Cuvier, F-75005 Paris, France..
    Sachs, Sven
    Nat Kundemuseum Bielefeld, Abt Geowissensch, Adenauerpl 2, D-33602 Bielefeld, Germany..
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Joude, Issam B.
    Morrison Hershfield, 2932 Baseline Rd, Ottawa, ON K2H 1B1, Canada..
    Yazbek, Muhammed K.
    Al Baath Univ, Fac Sci, Geol Dept, Damascus Aleppo Highway, Homs, Syria..
    Godoy, Pedro L.
    Univ Sao Paulo, Inst Biosci, Dept Zool, BR-05508090 Sao Paulo, SP, Brazil.;SUNY Stony Brook, Dept Anat Sci, Stony Brook, NY 11794 USA..
    Langer, Max C.
    Univ Sao Paulo, Dept Biol, FFCLRP, Ave Bandeirantes 3900, BR-14040901 Ribeirao Preto, SP, Brazil..
    Recovering lost time in Syria: New Late Cretaceous (Coniacian-Santonian) elasmosaurid remains from the Palmyrides mountain chain2024In: Cretaceous research (Print), ISSN 0195-6671, E-ISSN 1095-998X, Vol. 159, article id 105871Article in journal (Refereed)
    Abstract [en]

    Despite its relatively limited vertebrate fossil record, Syria currently records the largest number of documented Mesozoic marine reptile occurrences among the Middle Eastern countries. In particular, the phosphatic deposits of the Palmyrides mountain chain have yielded fossils of aquatic squamates, bothremydid and chelonioid marine turtles, as well as elasmosaurid plesiosaurs. Nevertheless, new discoveries have not been reported for the last two decades. Here, we describe the partial skeleton of an elasmosaurid plesiosaur from Syria, which comprises the middle and posterior cervical series, together with articulated pectoral, dorsal and anterior caudal parts of the vertebral column, with associated rib fragments. The fossil was excavated from Coniacian-Santonian phosphatic deposits of the Al Sawaneh el Charquieh mines, in the central part of the southwestern Palmyrides, about 200 km northeast of Damascus. The specimen can be assigned to Elasmosauridae based on the cervical centra morphology and, although incomplete, is significant because it not only represents likely the oldest, but also the currently most complete plesiosaur skeleton recovered from the Middle East. (c) 2024 Elsevier Ltd. All rights reserved.

  • 49.
    Ali, Moamen
    et al.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates.;Khalifa Univ Sci & Technol, RICH Ctr Res & Innovat CO 2 & H 2, POB 127788, Abu Dhabi, U Arab Emirates.;Assiut Univ, Dept Geol, Assiut, Egypt..
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Bosworth, William
    Apache Khalda Corp LDC, 11 St 281, Cairo, Egypt..
    Ligi, Marco
    CNR, Ist Sci Marine, Via Gobetti 101, I-40129 Bologna, Italy..
    Ball, Philip J.
    Keele Univ, Fac Nat Sci Geog Geol & Environm, William Smith Bldg, Newcastle Upon Tyne ST5 5BG, Northumberland, England..
    Decarlis, Alessandro
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates.;Khalifa Univ Sci & Technol, RICH Ctr Res & Innovat CO 2 & H 2, POB 127788, Abu Dhabi, U Arab Emirates..
    Geometry and kinematics of the Middle to Late Miocene salt tectonics, central Egyptian Red Sea margin2023In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 176, article id 104955Article in journal (Refereed)
    Abstract [en]

    The Red Sea basin includes a thick Middle to Late Miocene evaporitic succession that underwent halokinesis and caused intensive reshaping of the seafloor and the development of salt-tectonic structures. However, the ge-ometry and kinematics of these structures are still poorly understood. This study uses 2D and 3D seismic surveys and well data of the northern Egyptian Red Sea to systematically describe the distribution and morphology of salt structures, discuss their initiation, and construct a kinematic model for their origin. Our results indicate that the massive salt layer developed into five major NW-SE to NNE-SSW trending salt walls, characterized by relatively irregular crests and moderately dipping flanks. In addition, several symmetrical and asymmetrical folds and two categories of normal faults (subsalt and suprasalt) have been recognized. Based on our observations, salt mobilization in the study area started in the Late Miocene, during the precipitation of layered evaporites, and continued until the present day. In the northern Egyptian Red Sea, seismic interpretation indicates that hal-okinesis was triggered by a combination of thin-and thick-skinned systems, where the latter played a major role. The salt layer was welded during the Quaternary as several sags and grabens developed above the salt diapirs. Thick-skinned physical models are compatible with our observations, supporting the impact of basement faulting on Red Sea diapirism.

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  • 50.
    Allen, Rodney
    et al.
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Martinsson, OlofWeihed, PärUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Svecofennian Ore-Forming Environments Field Trip Volcanic-associated Zn-Cu-Au-Ag and magnetite-apatite, sediment-hosted Pb-Zn, and intrusion-associated Cu-Au deposits in northern Sweden2004Collection (editor) (Other academic)
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