Affiliation:
1. Volcano Science Center, U.S. Geological Survey, Menlo Park, California 94025, USA
Abstract
Abstract
In Mono Basin, California, USA, a near-circular ring fracture 12 km in diameter was proposed by R.W. Kistler in 1966 to have originated as the protoclastic margin of the Cretaceous Aeolian Buttes pluton, to have been reactivated in the middle Pleistocene, and to have influenced the arcuate trend of the chain of 30 young (62–0.7 ka) rhyolite domes called the Mono Craters. In view of the frequency and recency of explosive eruptions along the Mono chain, and because many geophysicists accepted the ring fracture model, we assembled evidence to test its plausibility. The shear zone interpreted as the margin of the Aeolian Buttes pluton by Kistler is 50–400 m wide but is exposed only along a 7-km-long set of four southwesterly outcrops that subtend only a 70° sector of the proposed ring. The southeast end of the exposed shear zone is largely within the older June Lake pluton, and at its northwest end, the contact of the Aeolian Buttes pluton with a much older one crosses the shear zone obliquely. Conflicting attitudes of shear structures are hard to reconcile with intrusive protoclasis. Also inconsistent with the margin of the ovoid intrusion proposed by Kistler, unsheared salients of the pluton extend ∼1 km north of its postulated circular outline at Williams Butte, where there is no fault or other structure to define the northern half of the hypothetical ring. The shear zone may represent regional Cretaceous transpression rather than the margin of a single intrusion. There is no evidence for the Aeolian Buttes pluton along the aqueduct tunnel beneath the Mono chain, nor is there evidence for a fault that could have influenced its vent pattern. The apparently arcuate chain actually consists of three linear segments that reflect Quaternary tectonic influence and not Cretaceous inheritance. A rhyolitic magma reservoir under the central segment of the Mono chain has erupted many times in the late Holocene and as recently as 700 years ago. The ring fracture idea, however, prompted several geophysical investigations that sought a much broader magma body, but none identified a low-density or low-velocity anomaly beneath the purported 12-km-wide ring, which we conclude does not exist.
Publisher
Geological Society of America
Reference54 articles.
1. Nature of the magma chamber underlying the Mono Craters area, eastern California, as determined from teleseismic travel time residuals;Achauer;Journal of Geophysical Research,1986
2. Other potential eruption centers in California: Long Valley–Mono Lake, Coso, and Clear Lake volcanic fields;Bailey,1982
3. Geologic map of Long Valley caldera, Mono-Inyo Craters volcanic chain, and vicinity, eastern California: U.S;Bailey;Geological Survey Map I-1933,1989
4. Volcanism, structure, and geochronology of Long Valley caldera, Mono County, California;Bailey;Journal of Geophysical Research: Solid Earth and Planets,1976
5. Excursion 13B: Long Valley Caldera and Mono–Inyo Craters Volcanic Chain, Eastern California;Bailey;New Mexico Bureau of Mines & Mineral Resources Memoir,1989
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