About This Item
Share This Item
Abstract
Journal of Sedimentary Research, Section
A: Sedimentary Petrology and Processes
Vol. 65A (1995)No.
1. (January), Pages 170-177
Geochemistry of Carbonate Cements in Surficial Alluvial Conglomerates and
their Paleoclimatic Implications, Sultanate of Oman
Stephen J. Burns, Albert Matter
ABSTRACT
Early diagenetic carbonate cements are a common feature of Quaternary alluvial
conglomerates in Oman. Cements are formed in the vadose and, more commonly,
phreatic zones from near-surface groundwaters. In drainage areas underlain
by the Semail Ophiolite, groundwaters have Mg2+/Ca2+
ratios greater than two, and cements are often dolomite or high-magnesium
calcite in addition to low-magnesium calcite. In drainage areas underlain
by limestone, groundwaters have Mg2+/Ca2+ ratios
of around one or less and cement mineralogy is nearly always low-magnesium
calcite. The oxygen and carbon stable isotopic ratios of the cements vary
widely, from -10.6
to + 3.0
PDB and from -10.0
to + 0.7
PDB, respectively. Cement d18O values
principally reflect variation in rainfall d18
over a time scale of several thousand years. Rainfall and cement d18O
values probably are inversely correlated with the mount of rainfall, which
is related to the frequency and intensity of the Indian Ocean monsoon.
Thus, cement d18O is potentially
a proxy indicator of relative rainfall and monsoon activity. For each of
three sampling areas, d13C is positively
correlated to d18O. Cement d13C
values are also related to rainfall amount because rainfall controls the
plant population. Greater plant respiration of isotopically depleted CO2
to shallow groundwaters and burial of organic material in conglomerate
deposits results in lower cement d13C
values compared to periods of lesser plant activity.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
| Watermarked PDF Document: $14 |
Watermarked Document – A Watermarked Document is branded with the name of the original licensed customer to discourage unauthorized users from sharing the document outside the user's organization. The PDF is no longer restricted to one machine, but can be circulated to others in the same company or department. A Watermarked Document also can be printed for hard copy distribution internally but is not authorized for outside distribution nor posting on the internet. Users will not be able to cut-and-paste text or images from one document to another.
|
| Open PDF Document: $24 |
Open Document – An Open Document is a fully functional PDF that can be circulated (a digital copy or hard-copy printed documents) outside the purchasing organization. Purchase of an Open Document does NOT constitute license for republication in any form, nor does it allow web posting without prior written permission from AAPG/Datapages ([email protected]).
|
GIS Map Publishing Program
