Smith, Roger Stanley Uhr (1976) Late-Quaternary pluvial and tectonic history of Panamint Valley, Inyo and San Bernardino counties, California. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06242009-141311
Panamint Valley was filled to overflowing on five, possibly six, separate instances, fed largely by runoff from the Sierra Nevada discharged through Owens and Searles lakes. These high water levels are best represented by uplifted lake terraces and associated deposits at Pleasant Canyon on the, west face of the Panamint Range, where shorelines at five, possibly six, levels have formed with respect to the level of Wingate Pass, (present elevation 1977 ±1 feet) into Death Valley. The level of this sill seems to have been tectonically stable, but was permanently raised about 50 feet by a mudflow which poured into the pass during a long-lasting lake stage, herein named Gale Stage. Paired Gale-Stage shorelines, attributed to lake stands stabilized at pre- and post-mudflow sill levels are found throughout Panamint Valley. The lower shoreline is 1.26 times older than the higher, more prominent shoreline, based on 1.26 times greater tectonic deformation at most localities. On the rising range block at Pleasant Canyon, the higher shoreline seems superposed on the lower to form a composite shoreline at 2177±10 feet elevation. Shoreline elevations at Pleasant Canyon (and probable uplift they experienced) are: 2410±10 feet (480±25 feet); 2298±10 (368±25); 2265±10 (335±25); 2177±10 (247±25 to 200±11); 2127±10 (150±11); and 2040±40? (63±41?). If the long-term uplift rate has been constant, the age of each shoreline should be proportional to its height above its sill level. Relatively steady deformation rates throughout Panamint Valley are suggested by the constant proportion (1.26:1.00) of deformation between the older (lower) and younger (higher) Gale-Stage shorelines.
A radiocarbon age of 31,150±1400 B.P. on snail shells establishes a minimum age for the shoreline at 2127 feet. Extrapolation using steady uplift rates indicates the following youngest-possible ages (in thousands of years) for the other uplifted shorelines: 2410 ft: 100±17; 2298 ft: 77±14; 2265 ft: 70±13; 2177 ft: 52 to 42±7; and 2040 ft?,: 14±10?. The probable age of each lake stage is about 20 per cent greater than its youngest possible age, a judgement based on correlation with the stages of Searles Lake (G.I. Smith, 1968).
The higher, younger Gale-Stage shoreline is prominent throughout Panamint Valley. Differential tectonic deformation of this feature amounts to about 370 feet, as established by a maximum elevation of 2190±10 feet on the central Panamint Range to a minimum of 1820±20 at Panamint Valley's north end. Deformation involves differential north- south warping of crustal block on both sides of the Panamint Valley and Ash Hill fault zones, which respectively define the east and west margins of Panamint Valley.
Right-lateral displacement of Quaternary features along the Panamint Valley fault zone exceeds their vertical, offset. Sixty feet of right-lateral offset have occurred since desiccation of the last, low lake to occupy Panamint Valley (15,000±5,000 B.P.), and cumulative offset of a sheet of monolithologic (landslide?) breccia of Plio-Pleistocene age from its probable source in Wildrose Canyon may total 10,000 to 15,000 feet.
Panamint Valley is abruptly and massively closed at its north end, where valley-floor deposits appear to underthrust Mesozoic plutonic rocks of Hunter Mountain along a northwest-trending zone which may represent the northwestward continuation of the Panamint Valley fault zone. Along the middle part of this reach of the zone, poorly-sorted (talus?) rubble of sound crystalline boulders underlies a 50 to 100-foot-thick zone of crushed crystalline rock which dips 17 to 35 degrees to the northeast beneath unshattered crystalline rocks. Thrusting may reflect a response to regional northwest-southeast right-lateral shear, possibly imposed upon classical Basin-Range bounding faults. The complex pattern of warping and faulting throughout the rest of Panamint Valley is also consistent with right-lateral shear, and the valley itself may have originated as a right-lateral "pull apart".
The unusually large volume of deposits along the 2177-foot shoreline suggests correlation with the Sierra Nevada Tahoe glaciation, which is distinguished by unusually large moraines. The small volume of 2127-foot shoreline deposits suggests correlation with the Tenaya glaciation, whose moraines are small. Thus the queried 2040-foot shoreline could represent the Tioga glaciation and the 2410-foot shoreline the Mono Basin glaciation. The 2265 and 2298-foot shorelines may represent early Tahoe events, suggesting that the Tahoe may be divided into early and late phases. Tentative ages of glaciations, based on correlation with pluvial events in Panamint Valley, are (in thousands of years B.P.): Mono Basin: 120±20; Tahoe (early): 92±15 to 78±15; Tahoe (late): 65±13 to 48±10; Tenaya: 38±6; Tioga?: 23±10?.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Geological and Planetary Sciences|
|Major Option:||Geological and Planetary Sciences|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||3 August 1975|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||24 Jun 2009|
|Last Modified:||26 Dec 2012 02:53|
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