Falling Stage Fluvial Deposition: A Source-to-Sink Perspective from Late Quaternary River Systems of the Texas Coastal Plain and Shelf

Mike Blum
Louisiana State University, Baton Rouge, LA

Research on large rivers systems of the Texas coastal plain and shelf demonstrate that fluvial deposition is common to the long and complex falling stages of 100 kyr glacio-eustatic cycles. This paper discusses how fluvial deposits from the last glacial period falling stage and lowstand can be traced directly from the mixed bedrock-alluvial valleys of the erosional continental interior to coastal plain incised valleys, and correlated to fluvial deposits within cross-shelf incised valleys that have been identified by seismic data.

Falling stage to lowstand fluvial deposition discussed herein are important for a number of reasons. First, their position deep within the valley fills makes preservation of falling stage to lowstand deposits in the stratigraphic record likely, and falling stage to lowstand sandbodies may comprise the bulk of reservoir-quality sands within many coastal plain and cross-shelf incised-valley fills. Second, the dimensions (widths and depths) of incised valleys directly reflects the scale and number of falling stage to lowstand channelbelts, and their degree of lateral vs. vertical amalgamation. Third, falling stage to lowstand channelbelts provide the critical link between erosional processes operating in continental interior source regions, and sinks within depositional basins for the 80% of the middle to late Pleistocene that is glacially-dominated, with sea levels significantly lower than present, and shorelines in mid-shelf or farther basinward positions.