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GEOREF RECORD

Absence of clay diagenesis in Cretaceous-Tertiary marine shales, Campos Basin, Brazil

S. M. Couto Anjos
Absence of clay diagenesis in Cretaceous-Tertiary marine shales, Campos Basin, Brazil
Clays and Clay Minerals (August 1986) 34 (4): 424-434

Abstract

In these shales which underlie the continental shelf off SE Brazil, mixed-layer illite/smectite (I/S) has remained randomly interstratified to depths of 3500 m and = or <100 degrees C, in contrast to the typical pattern of shale diagenesis in, for example, the Gulf Coast area. Clay minerals in samples from a Gulf Coast well off the Texas shore are I/S (montmorillonite-type), discrete illite, chlorite and minor kaolinite, whereas those from the Campos basin are kaolinite, clay-size biotite and I/S (nontronite-type). Kaolinite is abundant in the Campos basin well; and the variation in its abundance with depth seems to reflect variations in sea-level stands. The original composition of the I/S (nontronite-type) was probably the main factor controlling the lack of illitization in the shales of the Campos formation.


ISSN: 0009-8604
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 34
Serial Issue: 4
Title: Absence of clay diagenesis in Cretaceous-Tertiary marine shales, Campos Basin, Brazil
Author(s): Anjos, S. M. Couto
Affiliation: Pet. Brasil, S.A., Rio de Janeiro, Brazil
Pages: 424-434
Published: 198608
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 28
Accession Number: 1987-007577
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
S34°00'00" - N05°15'00", W74°00'00" - W34°00'00"
Source Note: John Hower Memorial Issue
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1987
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