Detrital zircon provenance and paleogeography of the Pahrump Group and overlying strata, Death Valley, California

Abstract

The Mesoproterozoic and Neoproterozoic Pahrump Group of Death Valley, California spans ca. 1300–635Ma and provides a >500 million-year record of geologic events in southwestern Laurentia. The strata analyzed include preserved sequences separated by unconformities recording syn-Rodinia basin development (Crystal Spring Formation); Rodinia stability; regional extension culminating in Neoproterozoic rifting of the Laurentian margin of Rodinia (Horse Thief Springs through Johnnie Formations); and multiple phases of glacial sedimentation and subsequent cap carbonate deposition (Kingston Peak Formation and Noonday Dolomite). U-Pb detrital zircon analyses were conducted on samples from the entire Pahrump Group and the Noonday Dolomite in the southeastern Death Valley region (20 samples, 1945 grains) to further constrain hypotheses for regional basin development during the development of the southwestern Laurentian margin.Our interpretation of provenance data expands upon and clarifies previous models defining a series of tectonostratigraphic units including: (A) the <1400Ma basal conglomerate of the Crystal Spring Formation, comprised of metasedimentary quartzite clasts, and exhibiting a unimodal detrital zircon sample distribution at 1690Ma with northerly source; (B) the ca. 1320–1080Ma Crystal Spring Formation exhibiting unimodal zircon distributions derived from southerly, local Paleoproterozoic basement sources punctuated by a ca. 300Ma duration unconformity; (C) the ca. 780–740Ma sequence of the Horse Thief Springs Formation, Beck Spring Dolomite, and KP1 unit of Kingston Peak Formation deposited in a marine basin with mixed southwestern Laurentian provenance; (D) a ca. 710–635Ma glaciogenic sequence (KP2-KP4 members of Kingston Peak Formation), recording the onset of Rodinia rifting, and Sturtian and Marinoan “Snowball Earth” intervals with provenance data suggesting derivation from erosion and recycling of older Pahrump Group strata; (E) the ca. 635Ma cap dolostone of the Sentinel Peak Member of the Noonday Dolomite, representing post-glacial drainage reorganization with more regional provenance; followed by (F) the <635Ma strata of the Radcliff Member of the Noonday Dolomite, showing a marked shift to bimodal age distributions, indicating derivation from local basement sources. These data synthesize and complement previous provenance studies from overlying units and result in the addition of ca. 500Ma of new provenance analysis for the southwestern Laurentian margin.