2019 AAPG Annual Convention and Exhibition:

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The Conversion of Tectonic and Climatic Forcings Into Stratigraphic Signals of Sediment Supply and Provenance

Abstract

Understanding how environmental forcings (e.g., tectonics, climate) are transformed by erosional landscapes into sedimentary signals is a critical component of efforts to invert the stratigraphic record and predict sediment characteristics ahead of drilling reservoir targets in frontier or under-explored basins. Previous research has largely focused on sediment supply (Qs) and grain size as the de facto sedimentary signals of changing forcing mechanisms. We consider the paired response of sediment provenance (Pv) and Qs to demonstrate that the same change in environmental forcing may have a different expression in the sedimentary record. Specifically, while Qs reflects integrated denudation across an erosional catchment, Pv is controlled by spatially variable erosion that occurs in transient landscapes. Increased Pv from proximal sediment sources is associated with upstream knickpoint migration that accompanies an increase in uplift rate or a decrease in precipitation. Pv from distal sediment sources increases when bedrock channels incise to produce lower gradient profiles associated with a decrease in uplift rate or an increase in precipitation. The peak Pv response is typically more rapid for changes in uplift rate whereas the peak Qs response is more rapid for changes in precipitation. These and other differences between the Qs and Pv signals may allow for a refined differentiation of the timing and mechanism of the forcing mechanism than possible via analysis of either signal alone. Correspondingly, our results also suggest that knowledge of external conditions may be useful in predicting sediment characteristics (e.g., Qs, Pv, and grain size) in the basin sink. Ultimately, the differential response of Qs and Pv to the same external forcing reflects distinct geomorphic processes that operate on different time scales. Future efforts to integrate multiple sedimentary signals may thus yield a clearer picture of the complex relationship between external forcings and resulting stratigraphy.