Emplacement mechanisms and trapping potential of gravity-driven allochthons
Gravity-slide blocks of Paleozoic carbonate detached from the Snake River Range show evidence of episodic emplacement into the Salt Lake group (Mio-Pliocene) in the Palisades reservoir area near Alpine, Wyoming. The allochthons lie in a large graben system created by the Grand Valley listric normal fault, a reactivated thrust that soles into a ramp in the underlying Absaroka thrust. In the Alpine 7 1/2-min quadrangle, one of the detached blocks is 2 1/2 mi (4 km) by 1 mi (1.6 km) in map view and contains the Ferry Peak thrust as well as other Laramide structures. Structures and formations of the Alpine allochthon may be matched to those in the range to restore approximate predetachment position. Very low-angle westward translation at or near the surface moved the blocks across the Grand Valley fault into the graben. The current location and attitude of these allochthons are due to subsequent movement and rotation on the Grand Valley fault. The allochthons occur at different stratigraphic levels in the Salt Lake group, each level corresponding to the time of a specific emplacement event. Catastrophic emplacement of a fractured allochthon, a potential reservoir, into a lacustrine or other source rock depocenter creates a unique and potentially predictable type of petroleum occurrence. Paleogeographic reconstruction may explain anomalous occurrence of discrete allochthons in structurally low areas where it can be shown that a gravitational potential existed for detachment and sliding. The resulting trap would consist of allochthons encased in autochthonous source rock.
- Research Organization:
- Univ. of New Orleans, Lakefront, LA
- OSTI ID:
- 5718460
- Report Number(s):
- CONF-850322-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 69:2; Conference: American Association of Petroleum Geologists annual meeting, New Orleans, LA, USA, 25 Mar 1985
- Country of Publication:
- United States
- Language:
- English
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