Covariance of structural and stratigraphic trends: Evidence for anticlockwise rotation within the Walker Lane belt Death Valley region, California and Nevada

Abstract

Large‐magnitude relative rotations of range‐scale structural blocks are inferred to be products of crustal extension in the Death Valley region, in California and Nevada. Reconstructions of the extended terrain restore pre‐Tertiary contractile structures with currently diverse trends into a relatively simple, north‐northeast trending thrust belt. We interpret trends of major contractile structures throughout the Death Valley region as characteristically discordant to, and thus geometrically independent from, stratigraphic trends. We compare trends of pre‐Tertiary contractile structures with paleoflow orientations in Lower Cambrian strata throughout the extended terrain. Significant differences between mean paleoflow orientations are consistent in magnitude and sense with differences observed in the structural trends. Available evidence does not support interpretation of paleoflow data from apparently rotated areas as representing an original paleogeography distinct from that of adjacent areas. Facies variations are present within the contractile structures. We interpret the strong covariance throughout the study area between structural and paleoflow trends of diverse orientations as evidence for vertical axis rotations. Combined rotation estimates from these data indicate clockwise rotations of 85° ± 12° for Bare Mountain and 73° ± 24° for the Striped Hills but anticlockwise rotations of 30° ± 35° and 87° ± 29°, respectively, for the northern and southern Grapevine Mountains. Such large rotations of opposite sense may be related to north‐south shortening accommodated by conjugate strike‐slip faults during large‐magnitude extension in the Death Valley region but are difficult to explain as products of regional dextral shear within the southern Walker Lane belt.