ABSTRACT

Matagorda Bay, one of the larger bays of the Texas Gulf Coast, lies in an interdelta position between the Colorado-Brazos River Delta and that formed by the Guadalupe and San Antonio Rivers. These deltaic deposits form a large portion of the Eunice-Oberlin Pleistocene plains.

The purpose of this investigation was to study and describe the Recent marine sediments of the bay floor and to determine the Recent-Pleistocene contact. The sediment samples were collected via piston coring tube along an east-west traverse across the Bay. The contact was determined from the sediment cores, jet-hole operations, and data from boring.

The Recent sediments can be divided into three main zones, A, B, and C. Zone A, the uppermost deposit, varies from a few inches in thickness, on the western shore where the Pleistocene is exposed, to about 2 feet in thickness. Zone B extends down to the Pleistocene contact and may attain a thickness of 40 or more feet. Zone C represents the oldest of the Recent deposits, and is found as a fill in the old Pleistocene channels.

Apparently the Pleistocene surface has been extensively entrenched, perhaps to a depth of over 78 feet below the present sea level.