Water Depths of the Mississippi River Delta Clinoform Break: Implications for Generating a Global Inventory of Post-LGM Relative Sea Level Rise Estimates

Abstract

A detailed analysis of 320 bathymetric transects quantifies the relationship between sea-level elevation and the Mississippi River Delta's clinoform break, i.e., the marine zone boundary between the sub-horizontal topset and basinward dipping foreset. Two distinct types of clinoform morphologies were observed. The first type, Type A, was found to be most common at mouths of distributary channels. Here, the change in seafloor slope at these clinoform breaks was abrupt, occurring over a distance of 1 ± 0.4 km with water depths of 3 ± 2 m. Type B, the second type, was typical at interdistributary areas. In the interdistributaries, the seafloor slope change was gradual, occurring over a horizontal distance of 3.4 ± 1.6 km with deeper water depths of 7 ± 4 m. The modern relationships between clinoform break and relative-sea-level (RSL) elevation at the Mississippi River Delta should apply to shelf-margin deltas formed during the last glacioeustatic lowstand. Given that lowstand deltas were constructed offshore of major rivers in many areas, it may be possible to apply the relationships shown here to the present-day elevation of intact lowstand clinoform breaks to generate a global inventory of post-glacial RSL rise estimates against which numerical models can be informed.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017