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AAPG Bulletin

Abstract

AAPG Bulletin, V. 91, No. 3 (March 2007), P. 287-320.

Copyright copy2007. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/10160606065

Impact of differential tectonic subsidence on isolated carbonate-platform evolution: Triassic of the Nanpanjiang Basin, south China

Daniel J. Lehrmann,1 Pei Donghong,2 Paul Enos,3 Marcello Minzoni,4 Brooks B. Ellwood,5 Michael J. Orchard,6 Zhang Jiyan,7 Wei Jiayong,8 Pete Dillett,9 Jon Koenig,10 Kelley Steffen,11 Dominic Druke,12 Jordayna Druke,13 Benjamin Kessel,14 Trent Newkirk15

1Department of Geology, University of Wisconsin–Oshkosh, 800 Algoma Boulevard, Oshkosh, Wisconsin 54901; [email protected]
2Department of Geology, University of Kansas, Lawrence, Kansas 66045; present address: University of Nevada–Reno, Reno, Nevada 89557
3Department of Geology, University of Kansas, Lawrence, Kansas 66045
4Department of Geology, University of Kansas, Lawrence, Kansas 66045
5Louisiana State University, Baton Rouge, Louisiana 70803
6Geological Survey of Canada, Vancouver, British Columbia, Canada, V6B 5J3
7Geological Survey of Guangxi, Guilin, Guangxi, People's Republic of China
8Guizhou Bureau of Geology, Guiyang, Guizhou, People's Republic of China
9Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Chevron North America Exploration and Production, McKittrick, California 93251
10Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Anadarko Petroleum Corporation, Houston, Texas 77251
11Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: ExxonMobil Upstream Research Company, Houston, Texas 77252
12Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Shell Exploration and Production Company, Houston, Texas 77079
13Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Hess Corporation, Houston, Texas 77002
14Department of Geology, University of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Anadarko Petroleum Corporation, Houston, Texas 77251
15Department of Geology, Univer sity of Wisconsin–Oshkosh, Oshkosh, Wisconsin 54901; present address: Newmont Mining Company, Elko, Nevada 89803

ABSTRACT

The Nanpanjiang Basin of south China contains four exceptionally well-exposed, isolated Triassic carbonate platforms. Detailed mapping of two-dimensional transects and description of stratigraphic sections allow the reconstruction of facies architecture, sequence stratigraphy, and evolution of the platforms. Biostratigraphy, magnetic-susceptibility profiles, and volcanic-ash horizons allow chronostratigraphic correlation and, thus, a basinwide evaluation of mechanisms controlling platform evolution.

A comparison of platform architecture demonstrates that southerly platforms have substantially greater thickness, backstepping geometry, pinnacle development, and earlier drowning that resulted from greater tectonic subsidence proximal to a probable convergent margin along the southern perimeter of the basin. Felsic volcanics thicken southward and contributed to the termination of the southernmost platform, indicating the development of a volcanic arc along the southern margin of the South China tectonic block. The northernmost isolated platform had greater longevity and lesser accumulation and lacks backstepping and pinnacle phases of development. Basin-margin intertonguing relationships, or lack thereof, demonstrate that earlier siliciclastic influx into the basin to the south and concurrent starved-basin conditions to the north impacted the evolution of platform-margin geometries.

Comparative analysis of platform evolution shows that the timing and rates of tectonic subsidence controlled the timing of platform termination by drowning, backstep geometries, pinnacle development, and overall platform thickness. The timing of siliciclastic basin fill dictated differences in platform-margin geometries such as slope angle, relief above basin floor, and the presence or absence of basinward platform progradation. Despite the dramatic differences in platform architecture, eustatic sea level fluctuations imparted a basinwide sequence-stratigraphic signal.

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