Comparing siliciclastic content of ramp to rimmed carbonate slope deposits during relative sea level highstand



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The Delaware Basin of west Texas is a world-class example of the reciprocal sedimentation model, which postulates that clastic sediment is delivered past exposed shelf to basins during relative sea level lowstands, whereas carbonate is produced on shelf and shed to basins during relative sea level highstands. However, visible volumes of siliciclastics are present in various highstand slope and basin carbonate deposits observed in the region, yet are absent in others. Shelf geometry may be a control on volume of siliciclastics delivered to the basin during highstands. Rimmed platforms appear more efficient at trapping sand and silt on-shelf than carbonate ramps, based on a higher Remaining Residue Fraction (RRF) occurring in slope and basinal carbonate deposits coeval to a rimmed platform. Detailed, measured sections of similar environmental facies coeval to both rimmed and ramp settings were assessed both proximally and distally within the Bell Canyon Formation (Guadalupian; rimmed) and Bone Spring Limestone/Cutoff Formation (Leonardian; ramp) to analyze the RRF weight percent. The proximal section coeval to the carbonate ramp has a significantly higher RRF weight percentage (22.77%) and grain-size (17.6 μm D50) than the other three sections (3.59%-6.50%; 8.37-11.2 μm D50). It also has more, and larger, detrital quartz grains than any other section. Therefore, coeval shelf geometry likely played a role in limiting detrital quartz grains from reaching the similar environment in the rimmed system. Additionally, greater transport distance from the shelf likely limited detrital quartz grains from reaching the more distal sections.



Delaware Basin, Reciprocal sedimentation, Carbonate, Siliciclastic, Mixed system