Connally, Thomas C.¹, Donald A. Rodgers²
(1) Landmark Graphics, Austin, TX
(2) Landmark Graphics, Houston, TX

ABSTRACT: Reactivated Forced Folds on the Arabian Peninsula

Producing fields and major structures of central Saudi Arabia and Kuwait are folds that are generally asymmetric with one shallow dipping limb and one steeply dipping limb. These structures were formed during the Carboniferous “Hercynian” orogeny and have been reactivated in the early Triassic, late Cretaceous and early Miocene. The “Hercynian” orogeny was a major structural event on the Arabian Peninsula and removed over 3000 feet of section from Khurais, the Summan Platform and other structural highs.
Present-day surface expression of Arabian structures is present at Ghawar, Dammam, and Khurais, where early Miocene Zagros uplift reactivated Cretaceous and older faults. The present structural forms in the subsurface and outcrop suggest that latest reactivation of these structures was due to compressional stresses because the fold axes are inclined toward the downthrown side of the faults. Published seismic, clay models, and comparison to analogous structures in America indicate that the present shape of the folds was produced by drape over high-angle reverse faults in the basement with the hanging wall moving toward the basins.
Conventional models of the “Hercynian” orogeny on the Arabian Peninsula suggest that the folding was produced by basement-involved high-angle normal faults. Clear evidence of later compressional reactivation suggests that the original “Hercynian” folding was also along high-angle reverse faults in the basement because it would be mechanically difficult to change the dip of basement faulting in order to produce the present structures. A compressional “Hercynian” origin for these folds in Arabia also predicts the presence of upturned Devonian rocks on the downthrown side of the fault, and an accumulation of eroded pre-Permian rocks in the early Permian Unayzah Formation on both sides of the fold.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.