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Tectonic Comparisons of Caucasus and California Cordillera

Michael E. Mulhern

Many parallels exist between the Caucasus region, shaped as the Eurasian and Arabian-African plates converged during the Cenozoic Alpine orogeny, and California, where the North American and Pacific plates interact. Since the Paleozoic, both areas have experienced repeated plate collision, subduction, terrane accretion, and mineralization.

The Forecaucasian platform hosts many large oil and gas fields in molasse-filled foredeeps of high heat flow. Production is from Permian to Pliocene tight anticlines on reverse faults, diapiric structures, shoestring sands of the prolific Maikop series, and Tertiary fanglomerates and sand lenses. Although not an exact parallel, this production suggests potential in Paleozoic and Mesozoic marine and Tertiary fanglomeratic, tuffaceous, and fluvial sediments in basins of the sparsely drilled Basin and Range.

The Greater Caucasus, like the Sierra Nevada, show Paleozoic-Mesozoic geosynclinal sedimentation, subduction, and granitic magmatism. The former have undergone much folding, thrusting, and Quaternary volcanism. Jurassic bituminous limestone is exposed, a source for the petroliferous Transcaucasian Intermontane depression. The latter is filled with thick Mesozoic-Cenozoic flysch and molasse and, like California's Great Valley forearc basin, orogenic terrane and permeable soils favor enology. Sources also include Eocene and Miocene diatomaceous and bituminous clays. Reservoirs include prolific Pliocene sands, Eocene olistostromes, fractured tuffaceous rocks, and Cretaceous-Miocene sandstones in anticlines and stratigraphic traps. Migration to basin flanks was aided by compression.

The Lesser Caucasus, a continuation of the main ophiolite foldbelt of Turkey, shares a subduction and accretionary history with the Franciscan melange. This microplate was obducted to Eurasia as the prong-shaped Arabian plate moved it and other microplates of the east Mediterranean in several directions (the Turkish microplate dextrally along the North Anatolian transform fault) and deformed wide areas.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.