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Morphology, internal structure and chemical composition of oxidized pyrite framboids from sediments of lake Baikal Siberia
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
2005 (English)In: Neues Jahrbuch für Mineralogie - Abhandlungen, ISSN 0077-7757, Vol. 181, no 2, 111-123 p.Article in journal (Refereed) Published
Abstract [en]

Scanning electron microscopy together with energy dispersive spectroscopy and electron microprobe analyses were used to study texture and chemical composition of oxidized pyrite framboids found in silty-clay horizons within the hemipelagic facies (upper 280 m) of 600-m-long BDP-98 sediment section from Lake Baikal. Since the framboids are sometimes extensively oxidized and loose their framboidal texture, they are often called herein with a general term "microspheroids". The microspheroids are usually 10 – 30 m in diameter, although some reach 60 m, and occur in clusters up to 2 mm large. Some of the microspheroids display framboidal textures on the surface while others are strongly oxidized and coated with goethite crusts. Gypsum crystals are often associated with the goethite-coated type of the microspheroids. Size distribution of the preserved pyrite framboids suggests diagenetic formation in anoxic zone of the sediment under the well oxygenated water column. The exceptionally large framboids suggest a low sedimentation rate at the cored site during glacial periods. Oxidation of the pyrite framboids can be related to diagenesis, which was associated with microbial activity and presence of oxidizing agents.

Place, publisher, year, edition, pages
2005. Vol. 181, no 2, 111-123 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-92129DOI: 10.1127/0077-7757/2005/0010OAI: oai:DiVA.org:uu-92129DiVA: diva2:165098
Available from: 2004-09-10 Created: 2004-09-10 Last updated: 2013-07-24Bibliographically approved
In thesis
1. Late Cenozoic Geoarchives from Lake Baikal, Siberia
Open this publication in new window or tab >>Late Cenozoic Geoarchives from Lake Baikal, Siberia
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Three long sediment cores (BDP-98 – 600 m, BDP-96 – 200 m and BDP-93 – 100 m) drilled in Lake Baikal (Siberia) have been studied with the aims of establishing an absolute chronology and reconstructing paleoclimatic and paleoenvironmental changes in the region. The location of the lake at relatively high latitude and continental interior and a thick continuous sedimentary archive that developed in a rift system tectonic setting provide unique material for this investigation. The cosmogenic isotope 10Be was used for dating and the results indicate time spans of 8 (+0.8\-0.6) Myr for BDP-98, 5.5 (±0.13) Myr for BDP-96 and >0.7 Myr for BDP-93. Two major sedimentary facies (deltaic and hemipelagic) are distinguished by textural geochemical and mineralogical data. Detrital mineral composition suggests negligible change in provenance during the period studied. Formation of authigenic minerals, such as framboidal pyrite, vivianite and siderite, reflects variable environmental conditions in the lake and climate change in the region. Biogenic silica content shows climatic influence, which is modified by the supply of detrital material and postdepositional alterations. 10Be dating, combined with lithological analysis of the sediments, makes it possible to place temporal constrains on climate cooling at the Miocene/Pliocene boundary (5 Myr ago) and at the Early/Late Pliocene boundary (3.6 Myr ago) as well as the beginning of the northern hemisphere glaciation at about 2.5–2.6 Myr ago. The regional east-west tectonic extension of south-east Asia, related to Tibetan Plateau uplift, was confined in the Baikal area to between about 7 and 5 Myr ago, with a rifting rate calculated at 7 mm year-1. Furthermore, the 10Be data suggest that geomagnetic field intensity strengthened around the Miocene/Pliocene boundary.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 64 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1013
Quaternary geology, Lake Baikal, Be-10 isotope, chronology, paleoclimate, tectonics, geomagnetic field, cosmic rays, Kvartärgeologi
National Category
urn:nbn:se:uu:diva-4552 (URN)91-554-6037-2 (ISBN)
Public defence
2004-10-01, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2004-09-10 Created: 2004-09-10Bibliographically approved

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