About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


AAPG Bulletin, V. 87, No. 5 (May 2003),

P. 781-815.

Copyright copy2003. The American Association of Petroleum Geologists. All rights reserved.

Regional sequence stratigraphic setting and reservoir geology of Morrow incised-valley sandstones (lower Pennsylvanian), eastern Colorado and western Kansas

David W. Bowen,1 Paul Weimer2

1Department of Earth Sciences, Montana State University, 895 Technology Blvd. South #103, Bozeman, Montana, 59718; email: [email protected]
2Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado, 80309-0399; email: [email protected]


David Bowen received his B.S. degree from Hobart College in 1978, his M.S. degree from Montana State University in 1980, and his Ph.D. from the University of Colorado in 2001. He is a consulting petroleum geologist with Savant Resources LLC and is an associate research professor at Montana State University. His current work focuses on the application of stratigraphy to exploration and exploitation problems in the western United States. His research interests include sequence stratigraphy, basin analysis, and the study of incised-valley-fill systems. David will be an AAPG Distinguished Lecturer in 2003–2004.

Paul Weimer holds the Bruce D. Benson Endowed Chair in the Department of Geological Sciences at the University of Colorado, Boulder and serves as director of the Energy and Minerals Applied Research Center. He is the current treasurer of the AAPG. In 2004, he will give the Society of Exploration Geophysicists Distinguished Instructor Short Course.


We thank AAPG reviewers James Coleman, Jr., William Goff, and James Rogers for their insightful reviews and AAPG Editor John Lorenz for his insight and help. An earlier version of the manuscript benefited from the reviews of Andy Pulham, Mary Kraus, Jack Edwards, and Roy Kligfield. We thank several of our colleagues for many lively discussions concerning the Morrow sandstone: Lee Krystinik, Beverly Blakeney-DeJarnett, Al Scott, Steve Gillis, Paul Dowden, Ross Mathews, Stuart Strife, and Dick Castle are especially noted. We thank Jay Austin and John Roesink for their help in drafting figures.


Oil and gas exploration for the lower Pennsylvanian Morrow Formation of eastern Colorado, western Kansas, and northwestern Oklahoma provides a subsurface data set that transects the entire range of lowstand depositional systems from incised-valley-fill systems to deep-water basin-floor systems in one composite depositional sequence. One compound incised-valley fill that is a part of this system contains three facies tracts with unique reservoir characteristics: (1) the updip facies tract is dominated by amalgamated fluvial channel sandstones, (2) the transition facies tract consists of fluvial channel sandstones interbedded with finer grained estuarine sandstones, and (3) the downdip facies tract consists of ribbonlike fluvial channel sandstones isolated in estuarine shale.

A 175-mi-long (283-km-long) longitudinal cross section through one trunk of the incised-valley-fill drainage shows that internal valley-fill strata change significantly as a function of the interplay of varying depositional systems down gradient in the valley. Key contrasts in reservoir performance are documented as a function of changes in reservoir characteristics, trap controls, and trap configurations from updip to downdip in this valley-fill drainage.

The strata of the Morrow Formation were deposited in a cratonic basin during a period in the Earth's history when the climate was cooler than today. High-frequency changes of sea level across an extremely low-gradient depositional surface controlled erosion and deposition. These facies tracts reflect the response of valley-fill sedimentary processes to high-frequency relative sea level changes resulting from glacio-eustasy. The resultant valley-fill systems have many characteristics in common with published valley-fill models, but have significant differences as well.

Pay-Per-View Purchase Options

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

Watermarked 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].