Geologic Report on a Portion of the Lang Quadrangle

Abstract

The area investigated in the Lang Quadrangle, California includes about seven square miles with desert vegetation and a maximum relief of about 1000 feet. The area consists of two formations separated by an angular unconformity of about 30 degrees, the Escondido tentatively placed in middle Miocene, and the Mint Canyon, either upper middle Miocene or lower upper Miocene. The Escondido formation consists of alternate beds of sandstones and shales and lava flows. The Mint Canyon formation is a series of sandstones, conglomerates, and coarse terrace gravels all of terrestial origin. The Escondido formation is folded into a tight pitching syncline with minor folds on it southern flank. A great deal of faulting has complicated the otherwise simple structure. The Mint Canyon formation is warped into a broad syncline and anticline which are almost exclusively depositional in origin. A great deal of minor faulting may be seen in this formation not to be correlated with that in the Escondido except in a few cases. The historical geology has been summarized on page 35. The economic deposits are unimportant and of no economic significance.