About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 48 (1964)

Issue: 4. (April)

First Page: 537

Last Page: 538

Title: Foraminifers from the Eagle Ford-Austin Contact, Northeast Texas: ABSTRACT

Author(s): C. L. McNulty, Jr.

Article Type: Meeting abstract


Relations of the Eagle Ford shale and overlying Austin chalk (Turonian-Coniacian) have been of recurrent interest for many years. Since the work of L. W. Stephenson, the formations have been considered more or less disconformable in northeast Texas. This paper reports foraminiferal data that bear upon the question.

Samples were collected across well exposed contacts at thirteen localities that extend from Austin, Texas, in the south to Honey Grove, Texas, in the northeast, an outcrop distance of approximately 400 miles.

Samples from the Eagle Ford shale are marked by a paucity of specimens, a low number of species, extreme rarity of benthonic forms, and consequent dominance of planktonics which consist mainly of Praeglobotruncana gautierensis. Exceptions to the foregoing occur at the south in the vicinity of Austin, Texas, where foraminiferal number increases to about 25/gram and benthonic components remain essentially unchanged, and at the extreme north, relatively near-shore position, where benthonics become dominant but foraminiferal number remains very low.

Samples from the Austin chalk are marked by high number of specimens, high number of species, dominance of planktonics, and a quantitatively minor but comparatively striking and diverse benthonic fauna. Exceptions to the foregoing are infrequent and sporadic. Lenticulina kansasensis is widely present at the Austin base and can serve as a marker.

From consideration of the foraminifers and regional stratigraphy, it is inferred that uppermost Eagle Ford sediments were deposited on a deeper and somewhat toxic sea floor. Some information suggests that contemporaneous

End_Page 537------------------------------

Austin-type sediments were accumulating upon an offshore bench or line of prominences. It is inferred that lowermost Austin sediments were deposited upon an offshore, relatively shallow and high-energy floor of likely high temperature and chlorinity.

End_of_Article - Last_Page 538------------

Copyright 1997 American Association of Petroleum Geologists