Comparative Analysis of the Western and Eastern Architecture of the Northern Margin of the Great Bank of Guizhou, Guizhou Province, South China
Kelley, Brian; Lehrmann, Daniel; Yu, Meiyi; Lau, Kimberly V.; Watford, Dylana; Shultz, James; Payne, Jonathan; Minzoni, Marcello
Carbonate platform development is controlled by several factors including carbonate factory type, basin topography, tectonics, climate, and siliciclastic flux. Because of its exceptional exposure, preservation, and temporal setting, the Late Permian to Late Triassic Great Bank of Guizhou (GBG) provides an outstanding opportunity to evaluate controls on platform architecture. The GBG is dissected by two synclines which expose the northern margin of the platform in cross section in both the western and eastern sectors. In this study, we combined satellite image analysis and field mapping to constrain the architecture of the northern margin of the GBG in the eastern sector near the town of Xiliang, Guizhou Province, south China, for comparison with the well-studied western sector near the town of Bianyang.
Our findings indicate significant differences in the architecture of the eastern and western sectors of the GBG, despite similarities in carbonate factory type and the general tectonic and climatic settings. In both the western and eastern sectors, the architecture evolved from a low-relief bank with oolite shoal margins in the Induan (early Early Triassic) to a steep platform profile in the Olenekian (late Early Triassic) and finally to a steep platform containing a Tubiphytes reef margin and slope in the earliest Middle Triassic. In both areas, the transition to a steep platform geometry preceded the appearance of organic boundstone, indicating that the margin was instead stabilized by early-marine cementation. During the Middle Triassic, however, the margin architectures diverged when siliciclastic turbidites from an eastern source began to onlap the Early Triassic carbonates of the prograded slope in the eastern sector. Following siliciclastic flux, platform carbonates prograded over the siliciclastic turbidites in the late Middle Triassic, resulting in two distinct intervals of carbonate slope progradation. In the western sector siliciclastic input was minimal. While the architecture of the eastern sector is dominated by two pulses of margin progradation, the western sector developed an aggrading erosional escarpment and bypass margin with greater syndepositional relief.
A comparison of the architecture of the northern GBG margin in the western and eastern sectors indicates that the timing and volume of siliciclastic influx played a significant role in determining the platform-margin architecture of the GBG.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013