About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 60 (1976)

Issue: 11. (November)

First Page: 2058

Last Page: 2062

Title: Globotruncana fornicata Zone of Upper Austin Group (Cretaceous), Northeast Texas: GEOLOGIC NOTES

Author(s): C. L. McNulty, Jr. (2)


The Globotruncana fornicata Zone is present in the upper part of the Austin Group at many localities in northeast Texas, where it contains several faunal changes. These include successively the extinction of Globotruncana concavata (Brotzen), the extinction of Citharina texana (Cushman), the appearance of Pseudogaudryinella capitosa (Cushman) and Pseudoclavulina clavata (Cushman), the appearance of Planoglobulina glabrata (Cushman), Loxostomoides cushmani (Wickenden), and Bolivinoides delicatula Cushman, and the appearance of Globotruncana elevata (Brotzen) s.l. Gaudryina austinana Cushman and G. ellisorae Cushman disappear within the zone but at relative positions that vary geographically.

The zone is about 50 ft (15.2 m) thick and confined essentially to the Burditt Marl of the Austin Group in Travis County (Austin area). It is present in the uppermost 35 ft (10.7 m) of the Austin in Dallas County. In Fannin County it includes the upper part of the Brownstown and the Gober, more than 400 ft (122 m) of section, although the distribution of Rugoglobigerina there causes some doubt of zonal interpretation.

Correlations of upper Austin rocks in northeast Texas implied by the G. fornicata Zone agree generally with those inferred from ammonite zonation. However, the planktonic foraminiferal framework results in different correlations to type sections in Europe.

As expanded, the G. fornicata Zone is applicable to all lithofacies in northeast Texas and provides a basis for definition of a provincial stage boundary.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Protected Document: $10
Internal PDF Document: $14
Open PDF Document: $24

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].