Arkosic alluvium derived from the Transverse Ranges and Tehachapi Mountains and deposited in the closed basin of the Antelope Valley, California, can be subdivided into eight mappable units. The six oldest units range in age from less than 0.5 m.y. through early Holocene and form widespread fill terraces and fans that extend over several thousand km2 of the valley floor. In contrast, the two youngest units, which consist of late Holocene and modern floodplain and channel sediments, are thin and of limited areal extent. The youngest of the six older deposits can be physically traced into nearly all drainages along both mountain ranges, which suggests nearly synchronous deposition across the region during latest Pleistocene to early Holocene time. These deposits appear to interfinger with and overlie pluvial lake deposits. The five older deposits can be recognized and correlated based on a combination of several factors such as similarity of soils, in situ shear-wave velocities, and degree of primary surface dissection. This evidence suggests that principal alluviation was regionally synchronous during the middle and late Pleistocene as well.
The existence of a pervasive and uniform sequence of apparently synchronous deposits throughout the region suggests that major aggradational and degradational episodes are controlled by regional climatic fluctuations. The existence of buried soils that require long periods of time for their formation further supports a climatic control of alluviation by suggesting that principal alluvial deposition is rapid and episodic. Finally, sedimentological evidence that indicates a change in hydrologic conditions during principal alluviation and an apparent correlation among major units in the Antelope Valley to those in the eastern San Joaquin Valley strongly suggest that aggradational episodes occur during major glacial to interglacial climatic transitions.