NEOPROTEROZOIC TO EARLY PALEOZOIC SEDIMENTATION HISTORY OF THE SOUTHERN GREAT BASIN (Invited Presentation)

The southern Great Basin of the United States hosts spectacular exposures of Neoproterozoic–early Paleozoic strata that record the evolution of the southwestern Laurentian margin from rifting to the establishment of a passive margin. Previous research has successfully applied quantitative basin analysis methods to characterize the post-rift thermal subsidence history, yet the tempo and timing of rifting remain elusive. Specifically, no consensus has been reached on the number of rifting events, their durations, or the age for the final rift–drift transition. In light of an updated timescale, as well as improved modeling designs, it is now worthwhile to reexamine these questions and the existing hypotheses.

Here we present subsidence analysis results for Neoproterozoic–early Paleozoic strata from the Death Valley and adjacent regions generated by SubsidenceChron.jl. This subsidence modeling program incorporates uncertainty in decompaction, backstripping, and instantaneous 1D age-depth modeling procedures for rift basins using Monte Carlo and Markov chain Monte Carlo methods. Using this approach, we perform sensitivity analyses to determine the effects of along-strike and depth-dependent facies changes on the modeling results. The tectonic subsidence curves for Tonian–Devonian strata highlight potential phases of extension and thermal subsidence. Subsequently, we focus on the final rifting event in order to invert for both the stratigraphic position and timing of the onset of passive margin sedimentation under a Bayesian framework. Our results provide a much improved time calibration for the Precambrian portion of the regional sedimentary successions, and also favor an early Cambrian placement of the final rift-drift transition that ultimately accommodated the thick early Paleozoic carbonate platform of western Laurentia.