Geological Society of America

T183 Sigma Gamma Epsilon Student Research (Posters)

Tuesday, 24 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

ANATOMY OF A PROGRADING LOWER TRIASSIC GIANT OOID-MICROBIAL CARBONATE SHELF MARGIN, NANPANJIANG BASIN, SOUTH CHINA

Paper number: T183-24
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Stephanie J. White Presenting Author
University of Alabama, Tuscaloosa, AL
Paul Enos
University of Kansas, Lawrence, KS
Marcello Minzoni
The University of Alabama, Tuscaloosa, AL
Souvik Bhattacharjee
University of Kansas, Lawrence, KS
Daniel Lehrmann
Trinity University, San Antonio, TX
Xiaowei Li
Stanford University, Stanford, CA
Brian M. Kelley
ExxonMobil Upstream Research Company, Houston, TX
Kimberly V. Lau
University of Wyoming, Laramie, WY
Meiyi Yu
Guizhou University, Guiyang, Guizhou
Jonathan Payne
Stanford University, Stanford, CA

Abstract

Continuous exposures of the Lower Triassic (Induan) margin of the Yangtze Platform at Zhenfeng, south China, reveal the architecture and evolution of a well-preserved oolitic-microbial carbonate system that developed after the end-Permian mass extinction and associated oceanographic perturbations. Detailed facies mapping along a faulted syncline that exposes a continuous transect through the platform interior, margin, and slope is integrated with δ¹⁶O and δ¹³C chemostratigraphy and analysis of concentration of redox-sensitive trace elements (e.g. V, Mo, Cr, U, I) to assess controls on carbonate factory type, facies distribution, and large-scale geometries of the platform margin and slope.

In the aftermath of the extinction that wiped out most of the calcifying metazoans, high rates of carbonate sediment production at the shelf margin and upper slope was maintained by microbialites and, principally, by abiotic production of giant ooids and early marine cements. Sediment production in the platform interior was dominated by carbonate mud, possibly abiotic, and a sparse, mostly molluscan fauna. Downslope reworking of this sediment, especially ooids, contributed to the development of steep (up to 15^o), prograding clinoforms, consisting of gravity-flow deposits, including, rarely, matrix-poor breccia. By the end of the Induan the shelf margin had prograded several kilometers and had attained a relief of approximately 400 meters above a sediment-starved basin.

Preserved geometries and facies architecture of the Induan Yangtze Platform at Zhenfeng demonstrate that active carbonate sediment production occurred even in the near-total absence of calcifying metazoans and algae and that accumulation rates of the combined giant-ooids and microbial factories were sufficient to keep up with subsidence and even to prograde several kilometers. These observations should improve interpretations of analogous carbonate reservoirs, such as the Jurassic Smackover Formation of the Gulf of Mexico, and general understanding of the controls on carbonate factories and their impact on facies architecture and large-scale geometry of carbonate systems.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-338153

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.