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Origin and timing of siderite cementation in Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. (Sedimentary Petrology)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. (Sedimentary Petrology)
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2006 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 23, no 4, 459-471 p.Article in journal (Refereed) Published
Abstract [en]

The origin and timing of siderite cementation have been constrained in relation to depositional facies and sequence stratigraphy of Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya. Optical microscope, backscattered electron imagery, and carbon and oxygen stable isotope analysis have revealed that siderite is of eo- and mesogenetic origin. Eogenetic siderite is Mg-poor with a mean composition Of (Fe91.7Mg1.5Ca0.3Mn6.5)CO3, and occurs in paraglacial, tide-dominated deltaic highstand systems tract (HST) sandstones, in paraglacial, foreshore to shoreface HST sandstones and in postglacial, Gilbert-type deltaic lowstand systems tract (LST) sandstones. This siderite is typically of meteoric water origin that influxed into the LST and HST sandstones during relative sea level fall and basinward shift of the strandline.Mesogenetic siderite, which engulfs and thus postdates quartz overgrowths and illite, is Mg-rich with a mean composition of (Fe72.2Mg21.7Ca0.8Mn5.3)CO3 and occurs in the paraglacial, tide-dominated deltaic HST sandstones, in paraglacial foreshore to shoreface HST sandstones, in glacial, tide-dominated estuarine transgressive systems tract (TST) sandstones, in postglacial, Gilbert-type deltaic LST sandstones, and in postglacial, shoreface TST sandstones. delta O-18(V-PDB) values of this siderite, which range between -22.6 and -13.8 parts per thousand, suggest that precipitation has occurred from evolved formation waters with delta O-18 values between -14.0 and +1.0 parts per thousand and was either meteoric, mixed marine-meteoric and/or marine in origin by assuming postdating quartz overgrowths and illite temperature between 80 and 130 degrees C.

Place, publisher, year, edition, pages
2006. Vol. 23, no 4, 459-471 p.
Keyword [en]
siderite, glaciogenic sandstone diagenesis, sequence stratigraphy, depositional facies, Upper Ordovician, the Murzuq basin, SW Libya
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-19754DOI: 10.1016/j.marpetgeo.2006.02.002ISI: 000239289400003OAI: oai:DiVA.org:uu-19754DiVA: diva2:47526
Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Diagenesis and Sequence Stratigraphy: Predictive Models for Reservoir Quality Evolution of Fluvial and Glaciogenic and Non-glaciogenic, Paralic Deposits
Open this publication in new window or tab >>Diagenesis and Sequence Stratigraphy: Predictive Models for Reservoir Quality Evolution of Fluvial and Glaciogenic and Non-glaciogenic, Paralic Deposits
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Development of a predictive model for the distribution of diagenetic alterations and related evolution of reservoir quality of sandstones was achieved by integrating the knowledge of diagenesis to sequence stratigraphy. This approach allows a better elucidation of the distribution of eogenetic alterations within sequence stratigraphy, because changes in the relative sea level induce changes to: (i) pore water chemistry, (ii) residence time of sediments under certain near-surface geochemical conditions, (iii) variations in the detrital composition, and (iv) amounts and type of organic matter.

This thesis revealed that eogenetic alterations, which are linked to sequence stratigraphy and have an impact on reservoir quality evolution, include formation of: (i) pseudomatrix and mechanically infiltrated clays in fluvial sandstones of the lowstand and highstand systems tracts (LST and HST, respectively), (ii) kaolinite in tide-dominated deltaic and foreshore-shoreface sandstones of HST, Gilbert-type deltaic sandstones of LST and fluvial deltaic sandstones of LST, (iii) kaolinite and mechanically infiltrated clays in sandstones lying below sequence boundary, (iv) K-feldspar overgrowths in fluvial deltaic LST, (v) glaucony towards the top of fluvial deltaic LST immediately below and at transgressive surface (TS) and in foreshore and shoreface transgressive systems tracts (TST) below parasequence boundaries (PB) and maximum flooding surface (MFS), (vi) framboidal pyrite and extensive cementation by calcite and dolomite in foreshore and shoreface and tide-dominated deltaic TST, and shoreface and tidal flat HST bioclastic-rich arenites particularly in the vicinity of PB, TS and MFS, (vii) pervasive cementation by iron oxide in shoreface-offshore and shoreface sandstones of TST immediately below the MFS, (viii) zeolites and palygroskite in shoreface sandstones of TST and HST, particularly above PB, and (ix) cementation by siderite in Gilbert-type deltaic sandstones of LST, tide-dominated deltaic and foreshore-shoreface sandstones of HST and in tide-dominated deltaic sandstones of TST, particularly at MFS. Moreover, this thesis revealed that the distribution of eogenetic alterations strongly control, and thus provide information for constraining the distribution patterns of mesogenetic alterations, such as illitization of mechanically infiltrated clays and dickitization of kaolinite, and hence of related reservoir quality evolution of sandstones during progressive burial.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 127
Keyword
Earth sciences, Siliciclastic diagenesis, Sequence stratigraphy, Glacial and non-glacial, Fluvial, Paralic and shallow marine, Geovetenskap
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-6179 (URN)91-554-6415-7 (ISBN)
Public defence
2005-12-12, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2013-05-15Bibliographically approved

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