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Mg-rich ferric illite in marine transgressive and highstand systems tracts: Examples from the Paleoproterozoic Semri Group, central India

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Title Mg-rich ferric illite in marine transgressive and highstand systems tracts: Examples from the Paleoproterozoic Semri Group, central India
 
Creator BANERJEE, S
JEEVARIKUMAR, S
ERIKSSON, PG
 
Subject sequence stratigraphy
vindhyan supergroup
southwestern oregon
chorhat sandstone
glaucony
origin
shelf
basin
sedimentation
stratification
ferric illite
semri group
paleoproterozoic
detrital k-feldspar dissolution
marine mg
epeiric shelf
tst and hst
low sedimentation rate
 
Description This paper focusses upon two glauconitic sandstones in the Paleoproterozoic Deoland Formation and Chorhat Sandstone, both belonging to the Semri Group, central India. In both the cases glauconitic minerals occur in sandstones deposited in the marine realm, within a transgressive systems tract (TST) for the former unit and within a highstand systems tract (HST) for the latter. The proportion of glauconitic minerals increases in the paleo-offshore direction. Petrography reveals selective early glauconitization of detrital K-feldspars along their fringes, cleavages and the fractures created by volume expansion during progressive alteration, leading to the generation of peloids with small relics of the precursors. XRD and mineral chemistry reveal a structure typical of glauconite, and more akin to Mg-rich ferric illite. The mineral chemistry of the glauconitic mineral phases remains the same whether the glauconitization process was incipient or at an advanced stage. These findings contrast with the previously held belief that ferric illite is confined to terrestrial or marginal marine sediments, and concurs with recent observations that the mineral can form in the open sea, but with high Mg. Since there are no ferro-magnesian minerals in association with these Vindhyan glauconitic sandstones, the seawater appears to be the only source for the Mg and Fe required. The general low rate of sedimentation on Proterozoic open shelves would have permitted ferric illite formation even within a HST, as represented by the Chorhat Sandstone. (C) 2007
 
Publisher ELSEVIER SCIENCE BV
 
Date 2011-07-25T20:02:16Z
2011-12-26T12:51:54Z
2011-12-27T05:38:41Z
2011-07-25T20:02:16Z
2011-12-26T12:51:54Z
2011-12-27T05:38:41Z
2008
 
Type Article
 
Identifier PRECAMBRIAN RESEARCH, 162(1-2), 212-226
0301-9268
http://dx.doi.org/10.1016/j.precamres.2007.07.018
http://dspace.library.iitb.ac.in/xmlui/handle/10054/6770
http://hdl.handle.net/10054/6770
 
Language en