BIOSTRATIGRAPHY OF THE LOWER CAMBRIAN IN SOUTHEASTERN CALIFORNIA

Mount, Jack D., Department of Earth Sciences, University of California, Riverside, California 92502

      Lower Cambrian litho-stratigraphic units of the Providence and Marble Mountains, San Bernardino County, California, consist of the following conformable formations from base to top: Zabriskie Quartzite, 22-151 m. (unfossiliferous); Latham Shale, 15-30 m.; Chambless Limestone, 32-68 m.; Cadiz Formation, 155-214 m. The Latham and Chambless Formations and lower beds of the Cadiz Formation constitute the late Early Cambrian Bonnia-Olenellus Zone which is divisible into two subzones. A new subzone from the base of the highly fossiliferous Latham Shale to 15-30 m. above the base of the Chambless Limestone is characterized by the first occurrence and range of Bristolia bristolensis (Resser) and has wide distribution in the Great Basin. Taxa apparently restricted to this unit are Bergaueria radiata Alpert, Paterina prospectensis (Walcott), Mickwitzia occidens Walcott, Hyolithes whitei Resser, Olenellus clarki (Resser), O. mohavensis (Crickmay), O. nevadensis (Walcott), Bristolia insolens (Resser), B. n. sp., Peachella iddingsi (Walcott), Onchocephalus n.sp., Anomalocaris sp.; the longer ranging Olenellus fremonti Walcott and 0. gilberti Meek have their first occurrences within this subzone.
      The youngest subzone of the Early Cambrian occupies the upper 17-38 m. of Chambless Limestone and lower 16-23 m. of Cadiz Formation. In addition to abundant Salterella sp., a few specimens of Billingsella highlandensis (Walcott), O. fremonti and 0. gilberti were obtained. Although this assemblage is not sufficiently distinctive for an adequate definition of the unit, the Cambrian sequences from the Death Valley- White-Inyo Mountains areas carry a fauna more characteristic of this subzone.
      The upper 139-191 m. of the Cadiz Formation carry faunas from the Middle Cambrian Plagiura-Poliella, Albertella and Glossopleura Zones.

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