Geology of a part of the Rosamond Hills area, Kern County, California

Abstract

An erosion surface of low relief was developed on the granitic complex of the Rosamond Hills area during the early part of the Tertiary period. Sometime during the Miocene epoch, faulting and volcanic activity formed a series of shallow lakes in which pyroclastic debris accumulated to a maximum depth of 900 feet to form the lower part of the Rosamond series. Deformation and volcanic activity culminated with the elevation of a mountain range of considerable relief, the outpouring of a comparatively large amount of rhyolite, and the ejection of much pyroclastic debris. A series of alluvial fans or bajada de posits with inercalated layers of pyroclastic debris accumulated along the margin of this mountain range to a maximum thickness of about 500 feet to form the upper part of the Rosamond series. The area was subsequently tilted southward, and erosion removed the Rosamond series from the tilted block except for a narrow strip along its sou thern margin. Hillocks formed by erosion of this strip of Rosamond rocks constitute the Rosamond Hills. Recent faulting along the southern margin of the Hills has probably helped to form Rosamond Lake.