A Facies Model for Shallow Coastal Ponds and Its Bearing from a Proposed Mid-Holocene Highstand Within the Northwestern Gulf of Mexico

Alexander R. Simms¹, Niranjan Aryal¹, and Yusuke Yokoyama^2
1Boone Pickens School of Geology, Oklahoma State University, Stillwater, OK
²Department of Earth and Planetary Sciences, University of Tokyo, Tokyo, Japan

The deposits from small lakes and ponds along the margins of estuaries and lagoons contain valuable records of paleo-sea level, past storm frequencies, and climatic change. Critical to their use in such studies is an understanding of their evolution and resulting facies patterns. Using aerial photos, surveyed elevation profiles, and vibracores, we describe the geomorphic/stratigraphic evolution of ponds whose floors range in elevation from -0.5 to +2.0 m above sea level on the margins of Baffin Bay in southern Texas. These ponds are in various stages of evolution providing an excellent opportunity to study their evolution and resulting facies patterns. We see a three-stage evolution of 1) dune blowout and creation of freshwater pond, 2) creation of a pathway to the open bay via headward eroding gullies, and 3) open communication with the bay via a small tidal inlet. Each of these stages of evolution has a unique sedimentary facies associated with it. In particular, we suggest that the percentage of carbonate and gypsum within the greater than 63 micron fraction can be used as a proxy for estuarine influence. Combined with elevation and age control, the sedimentary facies from these ponds are used to evaluate a proposed mid-Holocene sea-level highstand. Facies from these ponds suggests sea-level did not reach above -1.2 m until sometime after 4.8 ka.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas