PALEO-GEOMORPHOLOGICAL RESTORATION OF SOURCE-TO-SINK SYSTEMS: AN EXAMPLE FROM THE HUILU LOW UPLIFT IN THE PEARL RIVER MOUTH BASIN, SOUTH CHINA SEA

Understanding the relationships between paleotopography, geologic structures, and sedimentary systems is critical to robust source-to-sink (S2S) analysis, but few methods exist to precisely and reliably reconstruct ancient systems, particularly in fault-controlled settings. Using an assumption of a balanced source-to-sink system, we propose a new method to restore and analyze paleo-geomorphological elements of ancient systems. The method is based on hierarchical division and mass balance of large S2S systems and can be used to reconstruct differential denudation, compaction, and settlement in one workflow. The steps involved include (1) identifying the catchment area and the limits of denuded and downlapping strata associated with each drainage in the S2S system using high-resolution 3D seismic data, (2) structural restoration of any late-stage deformation, (3) recovery of denuded volumes where strata are eroded, and (4) calculation of the denuded volume for each catchment using the BQART model. We apply the technique to an example from the Paleogene Wenchang Formation in Huilu low uplift, Pearl River Mouth Basin, South China Sea, where six small-scale drainages systems are documented, linking the local source region to its adjacent sink. Three of the drainages have large catchment areas and gentle gradients (＜8°) and limited changes in sedimentary facies. The other half are examples of drainages with relatively small catchments and steep gradients (＞8°) that are tied to the development of abnormal fan delta systems. The reconstruction of paleogeomorphology based on S2S linkage corrects what appears to be incompatible facies given the modern gentle slope. This method and examples provide guidance for the analysis of the tectonic and sedimentary evolution of these systems, and for the reconstruction of ancient landscapes.