Controls on Seismic-Scale Geometries and Sequence-Stratigraphic Architecture of Mixed Carbonate-Siliciclastic Systems: Example from the Triassic Nanpanjang Basin, South China
Marcello Minzoni, Daniel J. Lehrmann, Paul Enos, Jiayong Wei, Meiyi Yu, Jonathan Payne, Xiaowei Li, Brian Kelley, "Controls on Seismic-Scale Geometries and Sequence-Stratigraphic Architecture of Mixed Carbonate-Siliciclastic Systems: Example from the Triassic Nanpanjang Basin, South China", Sequence Stratigraphy: The Future Defined, Bruce Hart, Norman C. Rosen, Dorene West, Anthony D’Agostino, Carlo Messina, Michael Hoffman, Richard Wild
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Comparative analysis of platform evolution recorded along multiple 2D platform-to-basin transects of the Triassic Yangtze carbonate shelf and several isolated platforms in the Triassic Nanpanjiang basin, south China, indicates that laterally variable tectonic subsidence, rate of basinal clastic deposition at the toe of slope, antecedent topography, and changes of carbonate factory type controlled the evolution, large-scale sequence stratigraphic architecture, and geometry of the platform margin and slope. Lateral and temporal changes in these parameters, and their various combinations during the Middle and early Late Triassic, were responsible for the remarkable vertical and along-strike variability in the observed platform architecture and slope profile.
Timing and rates of subsidence largely controlled along-strike variability, timing of drowning, back-step geometries, and pinnacle development. Antecedent topography and timing of clastic basin fill dictated differences in platform-margin stability and geometries such as slope angle, relief above basin floor, development of collapse scars, and progradation at basin margins. Changes in slope profile through the Early and Middle Triassic reflect changes in carbonate-factory type and evolving seawater chemistry following the end-Permian extinction. Eustasy, in contrast, had very little influence on platform morphology and large-scale architecture.
Process-based depositional models derived from the Nanpanjiang basin of south China present an important analog for understanding, quantifying, and predicting facies distribution and architectural styles at the basin scale in other systems, particularly in areas of active tectonism and temporal variations in oceanic conditions, such as, for example, the prolific Tertiary carbonates reservoir province of southeast Asia.