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Distribution of diagenetic alterations in glaciogenic sandstones within a depositional facies and sequence stratigraphic framework: Evidence from the Upper Ordovician of 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)
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: Sedimentary Geology, ISSN 0037-0738, E-ISSN 1879-0968, Vol. 190, no 1-4, 323-351 p.Article in journal (Refereed) Published
Abstract [en]

The spatial and temporal distribution of diagenetic alterations has been constrained in relationship to depositional facies and sequence stratigraphy of the Upper Ordovician glaciogenic quartzarenite sandstones in the Murzuq Basin, SW Libya, which were deposited during the Haritanian glaciation when the basin was laying along the continental margin of Gondwana. Eogenetic alterations encountered include: (i) replacement of detrital silicates, mud matrix and pseudomatrix by kaolinite in paraglacial, tidedominated deltaic, in foreshore to shoreface (highstand systems tract; HST) and in post-glacial, Gilbert-type deltaic (lowstand systems tract; LST) sandstones, particularly below the sequence boundaries (SB). Kaolinite fort-nation is attributed to the influx of meteoric water during relative sea level fall and basinward shift of the shoreline. (ii) Cementation by calcite (61 80VPD,3 = - 3.1 parts per thousand to + 1.1 parts per thousand and delta C-13(VPDB)=+ 1.7 parts per thousand to +3.5 parts per thousand) and Mg-rich siderite in the paraglacial, tide-dominated deltaic and foreshore to shoreface HST sandstones, in the glacial, tide-dominated estuarine (transgressive systems tract; TST) sandstones and in the postglacial, shoreface TST sandstones is interpreted to have occurred from marine pore-waters. (iii) Cementation by Mg-poor siderite, which occurs in the post-glacial, Gilbert-type deltaic LST sandstones and in the paraglacial, tide-dominated deltaic and foreshore to shoreface HST sandstones, is interpreted to have occurred from meteoric waters during relative sea level fall and basinward shift of the shoreline. (iv) Pervasive cementation by iron oxides has occurred in the glacial, shoreface-offshore TST sandstones and postglacial, shoreface TST sandstones immediately below the maximum flooding surfaces (NUS), which was presumably enhanced by prolonged residence time of the sediments under oxic diagenetic conditions at the seafloor. (v) Formation of grain-coating infiltrated clays mainly in the glacial, fluvial incised-valley LST sandstones and in the post-glacial, Gilbert-type deltaic LST sandstones as well as, less commonly, in the paraglacial, foreshore to shoreface HST sandstones and in the tide-dominated deltaic HST sandstones below the SBs.Mesogenetic alterations include mainly the formation of abundant quartz overgrowths in the glacial, fluvial incised-valley LST sandstones, post-glacial, Gilbert-type deltaic LST sandstones and glacial, shoreface TST sandstones, in which early carbonate cements are lacking. Illite, chlorite and albitized feldspars, which occur in small amounts, are most common in the glacial, tidedominated estuarine TST sandstones and paraglacial, shoreface HST sandstones. This study demonstrates that the spatial and temporal distribution of diagenetic alterations and their impact on reservoir-quality evolution in glacial, paraglacial and post-glacial sandstones can be better elucidated when linked to the depositional facies and sequence stratigraphic framework.

Place, publisher, year, edition, pages
2006. Vol. 190, no 1-4, 323-351 p.
Keyword [en]
sequence stratigraphy, depositional facies, glaciogenic sandstones diagenesis, Upper Ordovician, the Murzuq Basin, SW Libya
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-93822DOI: 10.1016/j.sedgeo.2006.05.020ISI: 000239749900019OAI: oai:DiVA.org:uu-93822DiVA: diva2:167423
Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2011-06-22Bibliographically 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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