ABSTRACT: Structural Control on Distribution of Sedimentary Facies in the Pennsylvanian Minturn Formation of North-Central Colorado

Karen J. Houck

Field study of individual sediment packages in the middle portion of the Pennsylvanian Minturn Formation of north-central Colorado has yielded evidence for structural influences on sedimentation in the area. The study area is thought to have been located south of an echelon offset in the fault zone bounding the eastern margin of the Central Colorado basin. Paleocurrent measurements show that drainages in nonmarine units and deltas and turbidites in marine units were repeatedly oriented southward throughout several shoaling-upward cycles of deposition. These trends are interpreted to be the result of a monoclinal ramp extending south from the offset zone through the study area and terminating in the southern part of the area. Mapping of individual sediment packages shows t at drainages and sites of delta and turbidite accumulation were repeatedly established near traces of two modern north-south-trending faults. Also, the packages thicken and become more completely preserved near the fault traces. These trends are interpreted to be the result of active movement on the faults during deposition of the study interval. The resulting fault-bounded blocks, delineated by facies and thickness changes, are similar in structural style to those identified by other workers in other parts of the basin.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990