Formerly aragonitic limestones associated with tillites in the late Proterozoic of Death Valley, California

The Upper Proterozoic Virgin Spring and Sour Dough limestones occur within the glaciogenic Kingston Peak Formation of the Death Valley region, eastern California. The Virgin Spring limestone is black, thinly laminated, and consists of microscopic spheroids and scattered ooids, contained within coarse neomorphic spar. An original aragonite mineralogy is inferred and this is supported by high contents of strontium (up to 3,650 ppm). Thin sandstone beds occur within the limestone, and their features suggest a storm origin. The Sour Dough Limestone has been metamorphosed and deformed but shows similar sedimentary structures and a high Sr content. Both limestones are interpreted as deeper-water, outer-shelf deposits, and their sedimentation is related to a sea-level rise through deglaciation. The Virgin Spring limestone has a typical marine delta ¹³ C signature (average +2.0 per thousand PDB), but the delta ¹⁸ O is very negative (-15.8 per thousand PDB). The latter is attributed more to the burial-diagenetic calcitization of an originally aragonitic sediment than to precipitation from ¹⁸ O-depleted seawater.