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Caliente Range and environs furnishes what is believed to be the best Miocene record for California. Approximately 180 molluscan and echinoderm faunas representing 47 nearly consecutive horizons from that of Turritella inezana var. hoffmani upward to well above that of Astrodapsis tumidus have been obtained from a Miocene succession locally about 13,800 feet in thickness. At Caliente Mountain a homoclinal section exposes, upward, successively about 1,100 feet of upper Oligocene(?), 4,500 feet of Vaqueros (lower Miocene), 4,700 feet of Temblor (middle Miocene), and 4,600 feet of Monterey (upper Miocene) strata. The marine Miocene series locally grades on the one hand to fine facies yielding foraminifers, and on the other to coarse continental facies yielding terrestrial ve tebrates. The district lies at the junction of the three largest Miocene provinces of the state, linking their histories.
The area discussed formed the pivotal part of a peculiarly long, narrow, and deep upper Oligocene and Miocene trough about 300 miles in length and 20 in width which seemingly extended from the Santa Cruz region southeast to Caliente Range. At this latter place the trough forked, sending a branch east into what is now the San Emigdio foothill region of southern San Joaquin Basin, with the original strike continuing southeast to intersect and die out in Ventura Basin. A thick marine succession along the axis of the trough grades on the flanks to thin wedges separated by unconformities that appear and grow strandward. Near its heads the succession locally passes into continental deposits with similar areal relations.
The trough was pinched out and strongly deformed and eroded by post-Miocene diastrophism. Its strata were steeply tilted, locally overturned and overthrust, and in places largely removed. Thrusts, erosion, slides, and alluvial debris have obliterated or hidden stretches near its mouth, both heads, and intermittently between these points.
Evidence secured in Caliente Range and environs, in combination with state-wide data, suggests the following history. In the lower Oligocene California seems to have been completely emergent, with continental deposits being locally laid down near the present coast. In the upper Oligocene the sea invaded the state as a narrow inlet occupying the newly initiated Caliente trough, continental deposition continuing in most former areas of that nature. The marine Miocene of California is a transgressive series, essentially conformable basinward, but revealing, strandward, the occurrence of two oscillations which respectively inaugurate and divide its upper third. It comprises three
nearly equal major natural divisions, the Vaqueros, Temblor, and Monterey stages, which approximate lower, middle, and upper Miocene. Each of these has a more or less distinctive epeirogenic history, fauna, and average physical aspect.
The sea transgressed throughout the Vaqueros stage, hesitated without receding, and then advanced more widely during the Temblor. Moderate regression accompanying diastrophism of locally prominent to locally imperceptible intensity and a widespread quickening of vulcanism then caused strandward unconformity. In early lower Monterey (Briones) time the sea again advanced widely. Its boundaries remained more or less static during the late lower Monterey (Cierbo). Moderate regression and diastrophism then again caused strandward unconformity. In upper Monterey (Neroly) time the sea once more advanced, reaching its widest extent during the epoch. The Miocene series records progressively cooler waters, the tropical Vaqueros fauna giving way to the subtropical fauna of the Temblor, and this n turn to the slightly hardier fauna of the Monterey. Each fauna changed relatively slowly during its stage, with hardier forms of the succeeding dynasty encroaching as an admixture in open, cooler waters, and then gave way to a new fauna with relative rapidity during a short transitional interval corresponding to one of the epeirogenic movements that divide the Miocene series of California into approximately equal thirds as regards major physical and coincident faunal units.
Wide regression resulting in almost or quite complete emergence of California separates the Miocene series from the markedly different and more restricted Pliocene series.
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