--> ABSTRACT: Central Caldera Collapse Complex--Implications for Extensional Tectonics for Basin and Range Province, by Leonid R. Koff; #91040 (2010)

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Central Caldera Collapse Complex--Implications for Extensional Tectonics for Basin and Range Province

Leonid R. Koff

The concentric patterns observed on the Earth's surface have been a point of intense controversy for many geoscientists. Pronounced concentric features have been widely observed on the Moon and other planets in the solar system. Serious observation of such concentric patterns on the Earth has been possible only since the advent of satellite technology. Concentric patterns on the Earth's surface have been ascribed to a variety of phenomena. According to traditional theory, the processes producing concentric patterns include volcanic and plutonic activity in the mantle and crust, and meteorite impact cratering. Prior to satellite observations, concentric patterns on the Earth were believed to have been eroded by natural processes. Now, however, geographic, topographic, and eomorphologic studies are being used to identify and map concentric patterns on the Earth's surface with a high rate of success.

The Basin and Range Province, being one of the youngest tectonically rejuvenated terrains, does exhibit a series of concentric patterns that are identifiable on a computerized, shaded, relief map. The concentric patterns in the Nevada and Utah portions of the Basin and Range coincide with the track of crustal plutonism and volcanism dating from the Cretaceous, and described in detail by G. P. Eaton in 1979. This observation implies a genetic relationship between plutonism and detected concentric patterns.

Numerous geotectonic and economic implications are associated with observed concentric patterns. These patterns appear to be centers of crustal extension and rifting. A gravitational collapse of the overlying sedimentary strata into the spreading centers results in observed thrusting, block faulting, and segmentation, resulting in megacaldera-like concentric rims. Most of the gravitational thrusting and imbrication is achieved by sedimentary plate movements on a low-angle detachment zone. This low-angle detachment zone, described by B. Wernicke in 1981, may be rooted in the lower crust.

The economic implications for mineral and hydrocarbon exploration are enormous in this province. Many researchers have identified an association of mineral accumulations and oil production with areas where concentric rims intersect with each other, or with straight lineaments.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.