Charles J. Stuart¹, Robert G. Hickman²

(1) Consultant, Park City, UT
(2) Structural Solutions, Sugar Land, TX

ABSTRACT: Tertiary Linked Extensional and Compressional Faults and Sedimentation in the Krishna-Godavari Basin, India

The Krishna-Godavari basin covers an area in excess of 40K km2, in onshore and offshore parts of east-central India. A zone of arcuate normal faults cuts Tertiary deltaic shelf margin and upper slope sediments that prograded across the rifted margin of the Indian plate. Normal faults converge basinward and form a decollement near the top of the Cretaceous section extending downslope into a linked complex of thrust faults and folds (toe-thrust complex). This complex is thrust over nearly undeformed basinal sediments. Mud-cored diapirs pierce fault-related structures mostly along the margins of toe-thrust complexes.

At least two episodes of toe-thrust formation occurred: the first culminating in the Eocene, and the second in the late Miocene or Pliocene. Younger normal faults sole-out and converge into a decollement at a shallower depth than Eocene faults.

Tertiary deltaic sediments prograded across syn-rift half-grabens filled with Cretaceous sediments. The steep depositional slope prevented extensive progradation and maintained a narrow shelf 30-40km wide. During highstands, shelfal and delta plain sediments primarily aggraded. During lowstands, sediments bypassed the narrow shelf and were funneled through canyons as mass flows and turbidity currents onto lower parts of the slope and the basin plain. This resulted in development of at least 6 unconformity bounded depositional sequences. Slope deposition was influenced by the rugose bathymetry produced by listric faults and toe thrusts. Sand-prone sediments probably accumulated in lows between actively growing toe-thrust folds and thinned over structural highs.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado