Geomorphic constraints on the incision history of the lower Kern River, southern Sierra Nevada, California

Abstract

Stream profile analysis of the lower Kern River and its tributaries help to constrain the landscape response to late Cenozoic tectonics in the southern Sierra Nevada of California. In this study, we identify two relict landscapes that have been offset from the Kern Plateau by periodic displacement along the southern Sierra Nevada fault system starting ca. 20 Ma. These remnants provide context from which to evaluate existing models of rock uplift and exhumation in the region. Reconstructed channel profiles on the relict landscapes indicate a slow incision rate of ~0.07 mm/yr throughout most of the Miocene. An increase in incision ca. 6 Ma resulted in the formation of the Kern Canyon. This increase in incision likely occurred in response to east-west delamination of a lithospheric root beneath the southern Sierra Nevada and is reflected in a pulse of vertical incision (~0.11 mm/yr) that has propagated upstream at a rate of ~7.3 mm/yr to its current position near Isabella Lake. Another two pulses of rapid incision were likely generated by increased rock uplift associated with the northward migration of the delamination hinge after 1 Ma. Incision rates of 0.58-1.2 mm/yr have propagated up the lower Kern River resulting in formation of the Kern River gorge. These new constraints on the incision history of the lower Kern River provide further corroborating evidence for existing models of late Cenozoic mantle delamination and associated epeirogenic processes that have helped shape the landscape of the southern Sierra Nevada.

Arrested development: Erosional equilibrium in the southern Sierra Nevada, California, maintained by feedbacks between channel incision and hillslope sediment production

“…1), which has been a nexus of research on mountain landscape evolution for more than a century (Lindgren, 1911;Hake, 1928;Panzer, 1933;Matthes, 1960;Wahrhaftig, 1965;Huber, 1981;Unruh, 1991;Small and Anderson, 1995;Stock et al 2004;Cassell et al, 2009;Gabet, 2014). Previous researchers have produced vast sets of geologic, geomorphic, geodetic, and isotopic data (House et al, 1997;Clark et al, 2005;Mulch et al, 2006;Cassel et al, 2009;McPhillips and Brandon, 2010;Hurst et al, 2012;Gabet, 2014;Hammond et al, 2016) that have helped constrain uplift, erosion, weathering, and river incision (House et al, 1998;Riebe et al, 2000;Granger et al, 2001;Wakabayashi and Sawyer, 2001; Riebe et al, 2001b;Stock et al, 2005;Dixon et al, 2009a;Riebe et al, 2015) across much of the mountain range and over timescales ranging from a few years to tens of millions of years (Saleeby et al, 2003;Stock et al, 2004;Hammond et al, 2016, Hunsaker andNeary, 2012;Wakabayashi, 2013;Sousa et al, 2016;Wheeler et al, 2016;Krugh and Foreshee, 2018). Most importantly for our study, many studies in the region have used cosmogenic nuclides to quantify both physical and chemical erosion rates (Granger et al, 1996;Small et al, 1997;Riebe et al, ...…”

Diverse Styles of Lithospheric Dripping: Synthesizing Gravitational Instability Models, Continental Tectonics, and Geologic Observations

“…(2012) lend support to the general idea of “gradual convective removal of the lithosphere” beneath the western U.S. by inverting the profiles of major drainage systems. River profile analysis (Krugh & Foreshee, 2018), uplifted marine deposits (Göğüş et al., 2017; Schildgen et al., 2012), and paleoelevation studies (Garzione et al., 2006, 2014; Hoke & Garzione, 2008; Sundell et al., 2019) show how quantitative landscape analyses can be used to test or refine hypotheses related to lithospheric dripping.…”

Late Cenozoic structure and tectonics of the southern Sierra Nevada–San Joaquin Basin transition, California

“…Deepening of the large west-flowing river channels may be linked to the ca. 10 Ma breakoff of the Sierran microplate from the Nevadaplano and west tilting (Unruh, 1991;Stock et al, 2005;Busby and Putirka, 2009) and to Pliocene epeirogenic uplift driven by mantle lithosphere delamination (Stock et al, 2004;Figueroa and Knott, 2010;Saleeby et al, 2013a;Krugh and Foreshee, 2018). In contrast, the southern ~100 km of the block diagram reveals much more local relief than regions to the north regardless of its lower position on the regional southward topographic gradient.…”

“…At the position of the arch topographic axis, proximal to the cover strata-basement contact, the uplift model predicts ~1000 m of surface and rock uplift. Regional surface uplift of the eastern and axial Sierra basement forced the deepening of major river channels and their proximal side creeks mainly in the Pliocene (Stock et al, 2004;Figueroa and Knott, 2010;Krugh and Foreshee, 2018) but drove very little erosion of the regional low-relief upland surface (Clark et al, 2005;Stock et al, 2005). In contrast, feebly-to non-lithified Neogene strata of the Kern arch and adjacent western Sierra were vigorously eroded by fluvial activity dispersed across the low-relief surface as the region rose in the Quaternary.…”