Nueces River Delta Plain of Pleistocene Beaumont Formation, Corpus Christi Region, Texas

Abstract

The surface of the Beaumont Formation in the Corpus Christi region of Texas preserves a relict depositional pattern laid down by a Pleistocene Nueces River during an interglacial or high sea-level stage like the present. The depositional pattern can be interpreted either as (1) that of a small meandering stream, similar to the present Nueces, undergoing numerous course changes (avulsions) and terminating in a small delta, or (2) that of a large multi-active distributary delta, similar to the present Mississippi River. Hydrologic considerations and comparisons with the contemporaneous Trinity, Brazos, and Colorado delta plains, some of their Holocene successors, and the Holocene Rio Grande and Mississippi deltas seem to rule out the second hypothesis. The sediments directly underlying the delta plain are largely fine grained--about 75 percent clay and about 25 percent very fine to fine sand. Both the areal extent and the assignment of the delta plain to the Beaumont Formation are controversial. Early mappers depicted it as larger in area. Most recent workers have assigned it to the Montgomery Formation (upper Lissie) or its equivalents. Depositional patterns, local surface gradient changes, and air photo patterns are of greater utility in correlation than similarity of regional gradients and soil types upon which previous correlations were based. A consequence of this assignment is the contemporaneity of the Beaumont-age delta plain and the relict Ingleside barrier offshore from it.