Skip to Main Content
Book Chapter

Facies Characterization and Architecture of a Muddy Shelf-Sandstone Complex: Mancos B Interval of Upper Cretaceous Mancos Shale, Northwest Colorado-Northeast Utah

By
Rex D. Cole
Rex D. Cole
Unocal Corporation Science and Technology Division Brea, California 92621
Search for other works by this author on:
Robert G. Young
Robert G. Young
Consulting Geologist Grand Junction, Colorado 81506
Search for other works by this author on:
Published:
January 01, 1991

Abstract

The Mancos B interval of the Upper Cretaceous Mancos Shale is represented by up to 372 m of thinly interstratified clays tone, siltstone, and very fine- to fine-grained sandstone deposited offshore, below storm-wave base, in the Western Interior Seaway. The Mancos B is best developed along Douglas Creek Arch in western Colorado and eastern Utah, where it is a major producer of natural gas and a minor producer of oil.

Combined stratigraphic and sedimentologic data suggest that the Mancos B is a regressive prodelta-plume complex genetically related to deltaic systems active along the western shoreline of the seaway. In outcrop and subsurface cores, the Mancos B is characterized by lenticular, cyclic, upward-coarsening parasequences, ranging in thickness from 2 to 32 m, and composed of five main lithofacies: silty claystone, sandstone-claystone, sandy siltstone, bioturbated muddy sandstone, and sandy dolomite (as beds and concretions). Sedimentary structures include horizontal lamination, wavy lamination, lenticular bedding, flaser bedding, ripple lamination, and horizontal lamination. Paleocurrent measurements indicate an average sediment-transport direction to the southeast (111°). Trace fossils are characteristic of the Cruziana ichnofacies. Lateral lithofacies variations in Mancos B parasequences are characterized by transitions from bioturbated muddy sandstone lithofacies into sandstone-claystone lithofacies then into sandy siltstone or silty claystone lithofacies. Horizons of sandy dolomite lithofacies cap most parasequences and represent periods of low sedimentation.

You do not currently have access to this article.

Figures & Tables

Contents

Concepts in Sedimentology and Paleontology

The Three-Dimensional Facies Architecture of Terrigenous Clastic Sediments and its Implications for Hydrocarbon Discovery and Recovery

Andrew D. Miall
Andrew D. Miall
Geology Department, University of Toronto, Toronto, Ontario M5S 3B1, Canada
Search for other works by this author on:
Noel Tyler
Noel Tyler
Bureau of Economic Geology, The University of Texas at Austin, Austin, Texas 78713-7508 U.S.A.
Search for other works by this author on:
SEPM Society for Sedimentary Geology
Volume
3
ISBN electronic:
9781565762268
Publication date:
January 01, 1991

GeoRef

References

Related

Citing Books via

A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal