Book Description

Field study of the middle part of the Pennsylvanian Minturn Formation in the McCoy-Bond area of north-central Colorado has yielded evidence for structural influences on sedimentation. The McCoy-Bond area was probably located near an en echelon offset in the fault zone bounding the eastern margin of the basin. Paleocurrent measurements show that sediment transport in nonmarine drainages and in marine deltas and turbidites was consistently to the south during several transgressive-regressive intervals. These trends may have been controlled by a topographic low that extended south from the offset zone to a termination in the southern part of the area. Mapping of sediment packages shows that drainages and sites of delta and turbidite accumulation were repeatedly established near the traces of two north-south- oriented faults. The sediment packages also thicken and are more completely preserved closer to the fault traces. These trends suggest that these faults were active during middle Minturn deposition. Individual fault blocks delineated by facies and thickness changes are similar in structural style to the Vail-McCoy trough, the Avon-Edwards high, and the Eagle sub-basin defined by other workers and illustrate the control of structure on sedimentation in the central Colorado basin.