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Integrated Outcrop to Seismic Calibration of Depositional Sequences in the Upper Cretaceous Mesaverde Group, Rock Springs Uplift, Southwestern Wyoming

DEVLIN, WILLIAM J., KURT W. RUDOLPH, VICTOR D. RAHMANIAN, YOW-YUH CHEN, CHARLES E. PFLUM, and RAY C. WRIGHT, Exxon Production Research Co., Houston, TX

An integrated study of Upper Cretaceous strata in the Rock Springs uplift has established a detailed sequence stratigraphic framework in outcrop, biofacies, and well-log and seismic data sets. Third- and fourth-order sequences, component systems tracts, and attendant depositional facies are documented.

The physical stratigraphy from the outcrop is tied into the subsurface by correlation of measured sections with well logs from nearby coreholes. Physical surfaces (e.g., sequence boundaries, transgressive surfaces, surfaces of maximum flooding) and stratal stacking patterns identified in outcrop have direct counterparts in the well logs. Constructed well-log sections carry the sequence framework further basinward in the subsurface. Biofacies data delineate the third-order depositional cyclicity by indicating relative proximity to the paleoshoreline and paleobathymetric estimates.

Seismic data was acquired from the location of the outcrops into the Washakie basin, allowing for the direct integration and calibration of these data as well. Outcrop and well logs were tied to the seismic using synthetic seismograms. Reflection terminations on the seismic data are associated with both the third- and fourth-order physical surfaces identified in the outcrop and wells. Sequence boundaries exhibit truncation, toplap, and downlap, and maximum flooding surfaces are demonstrated to be downlap surfaces. Internal reflection geometry within sequences consists of low-angle, basinward-dipping clinoforms. Nonmarine strata exhibit shingled reflections in dip section and channelized to subhorizontal geometry in strike sections (in braided fluvial and coastal plain facies, respecti ely). Integration of all data bases thoroughly documents the sequence framework and provides compelling support for sequence stratigraphic methodology and interpretation in each individual data set.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)