Organic geochemistry across the Permian-Triassic transition at the Idrijca Valley, Western Slovenia

Details

Serval ID
serval:BIB_F8FFF3AFC96B
Type
Article: article from journal or magazin.
Collection
Publications
Title
Organic geochemistry across the Permian-Triassic transition at the Idrijca Valley, Western Slovenia
Journal
Applied Geochemistry
Author(s)
Schwab V.F., Spangenberg J.E.
ISSN-L
0883-2927
Publication state
Published
Issued date
2004
Peer-reviewed
Oui
Volume
19
Pages
55-72
Language
english
Abstract
Bulk and molecular stable C isotopic compositions and biomarker
distributions provide evidence for a diverse community of algal and
bacterial organisms in the sedimentary organic matter of a carbonate
section throughout the Permian-Triassic (P/Tr) transition at the Idrijca
Valley, Western Slovenia. The input of algae and bacteria in all the
Upper Permian and Lower Scythian samples is represented by the
predominance of C-15-C-22 n-alkanes, odd C-number alkylcyclohexanes,
C-27 steranes and substantial contents Of C-21-C-30 acyclic isoprenoids.
The occurrence of odd long-chain n-alkanes (C-22-C-30) and C29 steranes
in all the samples indicate a contribution of continental material. The
decrease of C-org and C-carb contents, increase of Rock-Eval oxygen
indices, and C-13-enrichment of the kerogen suggest a decrease in anoxia
of the uppermost Permian bottom water. The predominance of odd C-number
alkylcycloalkanes, C-27 steranes, and C-17 n-alkanes with delta(13)C
values similar to-30parts per thousand, and C-13-enrichment of the
kerogens in the lowermost Scythian samples are evidence of greater algal
productivity. This increased productivity was probably sustained by a
high nutrient availability and changes of dissolved CO2 speciation
associated to the earliest Triassic transgression. A decrease Of Corg
content in the uppermost Scythian samples, associated to a
C-13-depletetion in the carbonates (up to 4parts per thousand) and
individual n-alkanes (up to 3.4parts per thousand) compared to the Upper
Permian samples, indicate lowering of the primary productivity (algae,
cyanobacteria) and/or higher degradation of the organic matter. (C) 2003
Elsevier Ltd. All rights reserved.
Create date
26/09/2012 14:11
Last modification date
20/08/2019 16:24
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