UC Santa Barbara

Models for rifting of the supercontinent Rodinia suggest complete separation of the conjugate plate and development of a passive margin sometime from the early-Cryogenian – middle-Cambrian. New tectonostratigraphic reconstructions along two parallel transects in Southeast Death Valley (SEDV) depict a Tonian – Cryogenian rift basin formed against Paleoproterozoic basement. The Ediacaran – middle-Cambrian siliciclastic and carbonate sequence, originally interpreted as recording a tectonically active hinge zone across SEDV, is now constrained in space and time with new chemostratigraphic correlations within a regional and global geochronologic framework. These new tectonostratigraphic data indicate repeated transgressive-regressive stratigraphic sequences from the earliest-Ediacaran – middle-Cambrian atop the craton margin, or rift boundary, and support the model of pre-Ediacaran rifting of southwest Laurentia. Ediacaran unconformities appear to be erosional and the product of large eustatic change rather than Ediacaran reactivation of the rift. Furthermore, reconstruction of this Neoproterozoic basin defines a parautochthonous zone formed against the craton and inverted within the Clark Mountain thrust complex. New U-Pb geochronology from basement exposures in the eastern SEDV distinguish gneissic basement from widespread, highly-strained Mesozoic plutons associated with this crustal shortening and is defined by overlapping Ediacaran unconformities across this zone. New U-Pb geochronological minimum age constraints on ductile deformation in the western transect corroborate the model of basin inversion during Early-Cretaceous Sevier shortening at Clark Mountain.