Pace of landscape evolution in the Sierra Nevada, California, revealed by cosmogenic dating of cave sediments

Abstract

We report 26 Al/ 10 Be based ages of Sierra Nevada caves that constrain detailed late Pliocene and Quaternary river incision histories for five river canyons. Rapid incision of ϳ0.2 mm/yr from 2.7 to ca. 1.5 Ma slowed markedly to ϳ0.03 mm/yr thereafter, likely reflecting the combined effects of a transient erosional response to Pliocene rock uplift and periodic mantling of riverbeds with glacially derived sediment in the late Quaternary. While ϳ400 m of incision has occurred in the past 2.7 m.y., outpacing interfluve erosion and thereby increasing the local relief, canyons as deep as 1.6 km existed prior to that time. These new erosion rates strengthen the case for tectonically driven late Cenozoic uplift.

Transient thermal regimes in the Sierra Nevada and Baja California extinct outer arcs following the cessation of Farallon subduction

“…Furthermore, we show that lateral heating of the eastern the SN and PB blocks following the cessation of subduction resulted in thermal expansion and related flexural bending of the extinct outer arc blocks. The observed westward tilts of the SN block [Unruh, 1991;Wakabayashi and Sawyer, 2001;Stock et al, 2004] and the PB blocks [Ague and Brandon, 1992;Dickinson and Butler, 1998] can be linked to these thermal and mechanical events.…”

“…[49] Geomorphologic studies in SN show that this region has been tilting westward as a single block in the last 10-12 Ma with total uplift of 1.5-2.5 km at the eastern edge; most of the uplift occurring in the last 3 -5 Ma [Unruh, 1991;Wakabayashi and Sawyer, 2001;Stock et al, 2004;Clark et al, 2005]. In addition to its previous elevation as a volcanic arc [Bateman and Wahrhaftig, 1966;House et al, 2001], tilted uplift started approximately with the cessation of subduction and lead to exposure of a huge granitic belt [Bateman and Wahrhaftig, 1966;Hay, 1976;Crough and Thompson, 1977].…”

Geomorphology and paleohydrology of Hurricane Crawl Cave, Sequoia National Park, California

“…Geochronologic data from HCC were published in Stock et al (2004Stock et al ( , 2005aStock et al ( , 2005b. Paleomagnetic orientations of fine-grained sediments throughout the cave consistently indicated deposition during times of normal magnetic polarity.…”

“…The cave was discovered by national park staff and cavers from the San Francisco Bay area in 1986 (Despain, 1999;Stock 1999). The cave has varied morphologies that imply a varied and complex history.…”

“…Hydrologic research has identified the causes of unique aquifer behavior at Big Spring and Lilburn Cave (Abu-Jaber et al, 2001;Urzendowski, 1993), the relationships between surface and groundwater systems (Tinsley, et al, 1981;Tobin and Schwartz, 2012), and the importance of karst aquifers to river flow (Despain and Stock, 2005;Tobin and Schwartz., Submitted). Geomorphic histories of caves in the basin have provided insight into cave geomorphology (Despain and Stock, 2005;Despain et al, in review), geochronology (Stock et al, 2005b), and the history of regional mountain uplift and canyon incision (Stock et al, 2004;Stock et al, 2005a). These previous works have primarily focused on the two longest cave systems in the river basin, Lilburn Cave and Crystal Cave, with some additional work on large springs not associated with extensive cave passages.…”