|
Map Satellite This area, which lies immediately to the southwest of the San Andreas Fault, has an unusual outcrop of rocks in the late Cretaceous sediments exposed in the cliff face. These rocks match a similar formation on the northeast side of the fault, at Eagles Rest Peak which is located some 560 kilometers (350 miles) to the southeast.
The sediments contain a quartz-plagioclase arkose and distinctive mafic conglomerates--anorthosite gabbro, quartz diorite-quartz gabbro, and dense, dark, fine-grained volcanic and diabasic rocks. These unusual mafic debris require a special source, of which an ophiolitic oceanic crust is the best qualified. The nearest possible source is found in the area of Eagles Rest Peak where similar materials are present. Dating of the materials from the two localities gives a wide but grossly similar range.
Integrity: The area is now a private campground and the sediments are virtually undisturbed.
Use: Private
Ref: Ross, D. C., C. M. Wentworth and E. H. McKee, 1973. Cretaceous Mafic Conglomerate Near Gualala Offset 350 Wiles by San Andreas Fault from Oceanic Crustal Source Near Eagles Rest Peak, California. Jour. Res. U. S. Geol. Sur. 1 (l), pp. 45-52.
September 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman
|
