Invertebrate Paleontology of the Wilson Grove Formation (Late Miocene to Late Pliocene), Sonoma and Marin Counties, California, with some Observations on Its Stratigraphy, Thickness, and Structure

Abstract

6 Introduction 6 Previous Work 7 Discussion 1 2 Stratigraphy of the Wilson Grove Formation/geologic setting 1 2 Deep marine facies 1 4 Shallow marine facies 1 5 Transitional marine/continental facies 1 5 Thickness of the Wilson Grove Formation and its relevance 1 5 Basement structure 1 8 Faunal composition, preservation, and paleoecology 1 9 Faunal composition and preservation 1 9 Paleoecology 1 9 Bennett Valley 2 1 Bloomfield Quarry 2 1 Burdell Mountain 2 7 Ebibias Creek 2 7 Meacham Hill and vicinity 2 7 Petaluma 3 0 River Road 3 0 Roblar Road and vicinity 3 0 Salmon Creek and vicinity 3 3 South Valley Ford 3 3 Spring Hill 3 5 Steinbeck Ranch 3 6 Tomales Bay 3 7 Whittaker Bluff and vicinity 3 7 Wilson Grove 4 1 Other miscellaneous outcrops 4 5 Age 4 5 Numerical age 4 6 Paleontologic age 4 6 Age controls from units associated with the Wilson Grove Formation 4 6 Summary 4 7 Acknowledgements 4 9 References cited 4 9 Appendix 1 – Faunal notes 57 Appendix 2 – Fossil localities and occurrences 6 5 Plates 1. Outcrop of the Wilson Grove Formation with location of fossil localities, cross sections, and locality names (in red) used in text. 2. Cross-sections and graphic thickness determination for the Wilson Grove Formation, and a composite stratigraphic section with approximate location of fossil localities Figures 1. Schematic cross-section showing the stratigraphic relationship of the Wilson Grove and Petaluma Formations in northern Marin and southern Sonoma Counties, California 1 3 2. Outcrop of coarse-grained sandstone interbed near the base of the Wilson Grove Formation at “The Elephants” between Tomales and Dillon Beach 1 4 3. Hummocky cross-stratification at Steinbeck Ranch with diagrammatic Illustration of