The non-equilibrium landscape of the southern Sierra Nevada, California

Abstract

The paleoelevation of the Sierra Nevada, California, is important to our understanding of the Cenozoic geodynamic evolution of the North America-Pacific plate boundary, and the current debate is fueled by data that argue for conflicting elevation histories. The non-equilibrium or transient landscape of the Sierra Nevada contains information about both past and present controls on the topography of the range. Using geomorphology and thermochronometry, two parts of the landscape of different geodynamic significance and age can be identified: (1) a long-lived, slowly eroding low-relief highland or relict landscape, which we relate to a period of lower relief and elevation from 80-32 Ma; and (2) younger, rapidly-incising river gorges created by at least two stages of elevation and relief increase since 32 Ma. Our data argue for moderate range elevation of ~1500 m at the cessation of arc magmatism in Late Cretaceous time, followed by two events at between 32 and 3.5 Ma and since 3.5 Ma that increased the range elevation to the 4000 m observed elevation today.

Tectonic geomorphology of the southern Sierra Nevada Mountains (California): Evidence for uplift and basin formation

“…This two-phase uplift history is seen throughout the Sierra from the Kern River to the American River (Cecil et al, 2006). Late Cretaceous elevations were high enough to generate a rain shadow (Poage and Chamberlain, 2002) with an estimated crest elevation range of b1500 m (Clark et al, 2005). The second uplift phase in the late Cenozoic started between 5 and 10 Ma (Huber, 1981;Graham et al, 1988;Unruh, 1991;Wakabayashi andSawyer, 2001 Clark et al, 2005) and was dominated by westward tilting.…”

Quantifying the slip rates, spatial distribution and evolution of active normal faults from geomorphic analysis: Field examples from an oblique-extensional graben, southern Turkey

“…As published estimates of landscape response times to tectonic perturbation are typically of the order of 1-3 Myr (Whittaker et al, 2007b, and can be longer (e.g. Clark et al, 2005;Pelletier, 2007), this implies that "young" extensional basins (drained by sediment-starved bedrock catchments) are the most fertile targets for further investigation. Given the number of normal fault-bounded grabens for which some geological and structural data do exist, but where tectonic rates over time periods of ∼10 6 years are poorly constrained (e.g., much of the Western Anatolian Extensional Province), we believe this approach could be applied widely to many extensional systems.…”

Cosmogenic nuclide-based investigation of spatial erosion and hillslope channel coupling in the transient foreland of the Swiss Alps

“…They can not be used to identify channels through which the knickpoints have already passed. The abrupt jumps in slope area plots or inflections in the stream-long profile that normally mark knickpoints (i.e., (Clark et al, 2005) no longer appear after the knickpoint has migrated to the headwaters. The knickzones in the Fontanne basin have already migrated through many of the subcatchments.…”