Stable isotope constraints on the elevation history of the Sierra Nevada Mountains, California

Abstract

Research on the uplift history of the Sierra Nevada mountain range has yielded seemingly confl icting results. Some studies argue for substantial uplift within the past 3-5 m.y.; others suggest that high elevations may have existed since the Cretaceous. The rain shadow across the Sierra Nevada is associated with a strong isotopic gradient, with lower δ 18 O values in precipitation on the leeward side of the range. Reconstruction of the δ 18 O value of meteoric water as a monitor of paleoelevation has focused mainly on the leeward side of the Sierras, but interpretation of the results of these studies may be complicated by shifts in global climate and regional moisture sources. We address these concerns by analyzing the δ 18 O value of tooth enamel bioapatite from contemporaneous mammalian fossils on either side of the present Sierra range. By sampling across the range, δ 18 O differences induced by a rain shadow can be isolated from other complicating factors. Our results indicate that the Sierra rain shadow has existed since at least 16 Ma, which is an important constraint on models for the tectonic evolution of the western United States. Unfortunately, temporal resolution for localities is too coarse to differentiate between glacial and interglacial localities during the past 2 m.y., so we cannot evaluate if there was a latest Cenozoic pulse of uplift or elevation loss.

Eocene-Early Miocene paleotopography of the Sierra Nevada-Great Basin-Nevadaplano based on widespread ash-flow tuffs and paleovalleys

“…8; Wolfe et al, 1997;Horton and Chamberlain, 2006;Mulch et al, 2006;Crowley et al, 2008;Cassel et al, 2009aCassel et al, , 2009bCassel et al, , 2010Hren et al, 2010), although Molnar (2010) contested the signifi cance of the isotopic data. Based on estimates of crustal thickness and analogy to the Altiplano of the Andes, Best et al (2009) interpreted a paleodivide at an elevation of ~4 km.…”

Rise and fall of the Nevadaplano

“…This widespread peneplain stood high, judging from stable isotope palaeoelevation studies (Horton et al 2004;Horton and Chamberlain 2006;Mulch et al 2006;Crowley et al 2008). Its surface was covered in late Miocene time by a series of lahars, trachyandesites, basaltic lava flows, and associated volcanogenic sediments that extended EW across the ranges for , 200 km; this hinterland was then normal-faulted, uplifted, and dissected by more recent erosion (Jayko 2009;Van Buer et al 2009).…”

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

“…A similar pattern of elevation change was claimed by Wolfe et al (1997) using palaeobotanical data. Crowley et al (2008) analysed oxygen isotopes in mammalian tooth enamel and concluded that a Sierran rain-shadow had existed since at least 16 Ma. Kent-Corson et al (2006) conclude there is a growing body of evidence for a migration of high surface elevation from the northern to the southern Great Basin from the late Eocene to the Miocene.…”