Geology of Garner Valley and vicinity

Abstract

Garner Valley is a broad alluviated upland valley bordered by dissected alluvial fans and ringed by high ranges underlain by crystalline basement (Fig. 1). The valley floor at 1300 - 1400 m (4250 - 4600 ft) is paralleled to the north by the jagged spine of the Desert Divide of the southern San Jacinto Mountains at altitudes of 1800 - 2400 m (5900 - 7900 ft), and to the south by the gentler bulk of Thomas Mountain, at 1500 - 2076 m (4900 - 6811 ft). All three physiographic units are elongate northwest - southeast, paralleling both some of the old igneous structure and the Cenozoic San Jacinto fault system. The valley is drained westward through the fault-controlled steep-sided canyon of the South Fork of the San Jacinto River. Hemet Dam was constructed across the upper reaches of this canyon in the 1890's to provide water for irrigation in the San Jacinto Valley; Lake Hemet has been developed into a popular recreational facility since then.

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