Constraining the Uplift of the Southeastern Sierra Nevada, CA using
Multi-Mineral Detrital Thermochronology from Active Catchments
Abstract
Most thermochronological studies aimed at constraining exhumation rates
rely on bedrock datasets. Often, they involve the analysis of samples
collected along an elevation profile in terrains with high relief.
However, there are several limitations to this approach, most
importantly access to an appropriately steep traverse and sufficient
relief to overcome uncertainties, and to have a broad enough range in
closure ages as a function of elevation. Detrital thermochronology
offers an alternative approach which can mitigate these challenges
through coordinated dating of modern river sediments using multiple
thermochronologic methods. Modern detrital sediments from active
catchments provide an excellent source of material, typically rich in
rock-forming and accessory minerals. Detrital thermochronologic data for
material in sedimentary basins has been used widely to infer exhumation
histories of sedimentary source terrains, reconstruct paleorelief, and
evaluate spatial and temporal variations in erosion rates; however,
there have been comparably fewer studies that apply this technique to
evaluate regional exhumation patterns using detrital samples from active
catchments. Based on the approach presented in Gallagher and Parra,
(2020), we are exploring the capability of detrital thermochronologic
data to infer regional exhumation patterns in the southeastern Sierra
Nevada, CA. Here the uplift history remains debated and the potential
mechanism of uplift has yet to be thoroughly constrained. Many
catchments along the eastern side of the Sierra Nevada exhibit
advantageous characteristics for detrital thermochronologic studies,
including steep topography and high relief (that make it more difficult
to sample bedrock), limited lithologic variability (which minimizes
point-source biasing), relatively simple geologic structure, and
relatively easy access to detrital sampling localities. Additionally,
the dominant source of the southeastern Sierra Nevada catchments, the
igneous units of the Sierra Nevada batholith, include abundant
rock-forming minerals for 40Ar/39Ar thermochronology (hornblende,
biotite, and sometimes muscovite) as well as abundant accessory minerals
for (U-Th)/Pb geochronology(zircon), (U-Th)/Pb thermochronology
(apatite), and (U-Th)/He thermochronology (zircon and apatite).
Collectively, detrital thermochronological data from these minerals can
elucidate much of the post-crystallization thermal history of the
eastern flank of the Sierra Nevada. Preliminary results of this
technique demonstrate the potential of this cost- and labor-efficient
approach for exhumation history studies.