Geologic Map of the Whittier Hills: Supplement 1 from "Geology of the Whittier Hills, Whittier, California" (Thesis)

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This report is an attempt to unravel the structure of the very complicated western portion of the Puente Hills known as the Whittier Hills. The only comprehensive published study of it was made by English in 1926.(1) Of the Whittier Hills portion he said, "The Whittier Hills, comprising the area west of La Habra Canyon, show some of the most complicated structure to be found within this district. Steep irregular dips, numerous faults, unconformities, and lithologic variations in the different formations and members make the structure, as well as the stratigraphy, difficult to work out."(2) The mode of approach has been that of a very detailed examination in which every attitude available has been recorded. The petrographic interests have been sacrificed to permit a closer structural analysis of a larger area. Some semblance of order has thus been obtained for most of the area. The situation briefly is this: a section of upper Puente shale and part of the Repetto siltstone and conglomerate have been folded and faulted into apparently unrelated blocks. Included in these structures are one hundred mappable lithologic units, twenty-five different faults, and nine major folds. The most westerly portion of the Whittier Fault disappears in the area, and thereby presents the problem of determining its westward extension. The area has two distinct oil-producing fields and has been mapped by many oil companies in exploration for others. The folds mapped may thus be of interest from an economic point of view. 1. English, Walter A., Geology and Oil Resources of the Puente Hills Region, So. Calif., U.S.G.S. Bulletin 768 1926 2. Ibid, p.58

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