Atmospheric flow deflection in the late Cenozoic Sierra Nevada

Abstract

Given the intimate links between topography, tectonics, climate, and biodiversity, considerable effort has been devoted to developing robust climate and elevation histories of orogens. In particular, quantitative geochemical reconstructions using stable oxygen and hydrogen isotopes have been applied to many of the world's mountain belts. Recent advances in atmospheric modeling have suggested that such stable isotope records from leeward sites can be affected by the complicating role that sufficiently elevated topography such as the southern (High) Sierra plays in diverting atmospheric circulation. While such “terrain blocking” effects are a hallmark feature of modern atmospheric circulation in the Sierra, their evolution remains poorly constrained. In order to examine the history of these terrain blocking effects, we developed stable isotope records from three late Cenozoic sedimentary basins in the Eastern Sierra and Basin and Range: 1) Authigenic clay minerals in the Mio-Pliocene Verdi Basin (VB) near present-day Reno, Nevada, 2) Fluvial and lacustrine carbonates from the Plio-Pleistocene Coso Basin (CB) in the southern Owens Valley, and 3) Miocene to Holocene pedogenic, fluvial and lacustrine carbonates of Fish Lake Valley (FLV). Whereas both the VB and CB are proximal to the Sierra crest, FLV is a distal leeward site east of the White and Inyo Mountains in the Basin and Range. The CB oxygen isotope record exhibits an increase of 1-2‰ over the last 6 Myr while VB and FLV show no significant change. These results suggest that terrain blocking around the southern Sierra initiated prior to the late Cenozoic, though it may have been modestly enhanced during the last 6 Ma.