--> Abstract: Geochemical Attributes and Early Diagenesis of Neritic Cool-Water Carbonates: Central Southern Australian Margin, by John M. Rivers, Noel P. James, and T. Kurtis Kyser; #90039 (2005)

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Geochemical Attributes and Early Diagenesis of Neritic Cool-Water Carbonates: Central Southern Australian Margin

John M. Rivers, Noel P. James, and T. Kurtis Kyser
Queen's University, Kingston, ON

The southern Australian continental margin (CSAM) is the largest area of active cool-water carbonate deposition on the globe. Cool-water carbonates (CWCs) differ from their warm-water counterparts in that they form in waters with an average temperature of less than 20°C, have a characteristic biota which excludes zooxanthellate corals and green algae, and are dominantly of calcitic mineralogy. While the sedimentological attributes of modern CWC deposits are reasonably well understood, their early diagenetic pathways remain largely unstudied. It is fundamental to understand the processes that occur at or near the sea floor before sediment is buried because the product of such change directly controls subsequent diagenetic pathways, and hence reservoir potential. Techniques including thin-section petrography, X-ray diffractometry, SEM, EDX, microprobe, gas-source and inductively coupled-mass spectrometry have been employed to characterize samples of seafloor sediment collected across the CSAM. These optical and chemical analyses reveal distinct assemblages of carbonate sediment. Through 14C-dating, these assemblages have been categorized as (i) relatively pristine Holocene sediment (0-5 ky); (ii) sediment deposited and stranded during the last major transgression (5-18 ky); and (iii) iron-stained relict sediment deposited near or before the 25 k highstand. Here, a multiple-proxy approach is used to deconvolute geochemical alteration due to meteoric and seafloor diagenesis from primary oceanographic geochemical signals. This research allows us to broadly address how the sedimentology and geochemistry of the modern CWC environment relates to the rock record.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005