Ravenna Quadrangle (with index map of photographs): Supplement 2 from "Geology of the Ravenna quadrangle" (Thesis)

Description

The Vasquez Series, composed of coarse fanglomerates, finer sandstones, and lavas, represents sub-areal deposition in the form of a series of rapidly coalescing alluvial fans. These fans were formed in a basin entirely local in character (confined to the Ravenna and Lang Quadrangles) which was probably caused by faulting, either in late Oligocene or very early Miocene time. The sediments are early or early middle Miocene in age, are very well consolidated, poorly sorted, and broadly stratified. They occur associated with intrusions of quartz diorite, syenite, and anorthosite, contacting these formations either depositionally or by means of faults. The lavas are of both intrusive and extrusive origin. The extrusive type is both vesicular and amygdaloidal, while the intrusive type is massive. The section is broken by two major fault systems. The older of these, trending northwest-southeast, is represented by normal faults, whose movement is primarily vertical, while the younger system, trending nearly at right angles to the other, consists of steep strike-slip faults.

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