QUANTIFICATION OF CENOZOIC UPLIFT OF THE SIERRA NEVADA FROM SEDIMENTARY STRUCTURE OF THE CENTRAL VALLEY OF CALIFORNIA

Cenozoic tilting of the Sierra Nevada block was originally proposed by G.K. Gilbert in 1883, but still remains controversial. Most studies testing the hypothesis have employed geomorphological methods and tilted stratigraphic markers in the Sierra Nevada block, but these results have been challenged. A limited number of studies have used dips of sedimentary strata in the Central Valley, but not in a geographically systematic fashion. In this study I have produced cross sections from the middle of the Central Valley to the east side of the Sierra Nevada crest along the entire length of the range. The cross sections contain strong evidence in favor of Cenozoic tilting in the form of ancient shorelines that are as much as 2 km below sea level. Tilted strata in the Central Valley are consistent with the tilts of correlative stratigraphic markers on the Sierra Nevada block. For the northern Sierra Nevada, the data show only one major episode of tilting that began at ~4 Ma and ended 2 to 1 Ma. The southern end of the range, however has been continuously tilting since the Eocene, with a marked increase in the tilt rate at ~4 Ma, and has continued to increase to the present. Basin sediment deposition rates match closely with inferred tilt rate variations. This tilt history corresponds very well to the history of fluvial incision rates in the Sierra Nevada inferred from geomorphic evidence by Beeson and McCoy (2022). The temporal and spatial pattern of tilting since 10 Ma matches the spatial and temporal distribution of convective downwelling of dense lithosphere under the southern San Joaquin Valley, providing a tectonic mechanism for the late Cenozoic topographic rejuvenation of the Sierra Nevada.