Page 341 - Carbonate Facies in Geologic History

328 The Rise of Rudists; Middle Cretaceous Facies in Mexico and the Middle East

Table XI-I. Middle Cretaceous correlations in Mexico and Texas
Stage Central Mexico North Mexico Texas
Buda 1st.
Cuesta del
Cenomanian Del Rio
Cura shale

Albian

Otates La Pei'ia
Aptian Pine Island
shale shale

El Abra Formation and the intervening basinal limestone, the Tamaulipas (Ta-
bleXI-1). A northern shelf area marked by the outcropping Aurora Limestone
exists in Coahuila and Chihuahua.
Inasmuch as one of the great older oil fields of the world exists along the edges
of the Faja de Oro or Golden Lane platform, lying south of Tampico, the facies of
these rocks have been much studied by both Mexican and U.S.A. geologists in the
last 20 years, in hopes that the vast early production of the Mexican fields can be
extended into offshore areas around the margins of the Gulf. The offshore exten-
sion of the Golden Lane by Petroleos Mexicanos and the gas fields of the Stuart
City-Edwards Reef trend in south Texas have encouraged this study.
Facies have been described by Wilson et aI. (1955) on the El Doctor bank;
Barnetche and Hling (1956) on the Poza Rica field; Griffith et aI. (1969) on the
Cuesta El Abra and Deep Edwards reef trend; Bonet (1952) on the Golden Lane;
Becerra (1970) on Poza Rica; Carrasco (1971) on the Actopan platform; Rose
(1963), Keith (1963), and Bonet (1963) on the Golden Lane, Cuesta El Abra, and
Edwards trends, and Coogan et al. (1972) on Golden Lane and Poza Rica. The
following basic microfacies types are recognized in these strata. Despite some
differences in terminology, agreement is general about the definition of the rock
types and their environmental meaning. The outline below lists them in order of
facies progression from basin to shelf.
Basinal and basin margin (Standard Facies belts 1 and 3) (plate III).
Tamaulipas limestone of eastern Mexico; marginal slope facies of Carrasco, termed
planktonic micrite by Griffith et al. (1969). In northern Mexico the thicker-bedded facies is
included in the basinal Aurora and the thin-bedded, rhythmic Cenomanian facies of the
Cuesta del Cura Formation.
Pelagic lime mudstone and wackestone. Dark to light gray, evenly bedded with stylolitic
contacts along clay seams and organic films. Many dark chert layers are present. Thin (10-