Early Eocene marine ostracods from the Crescent Formation, southwestern Washington State, USA

Tatsuhiko Yamaguchi,James L Goedert

doi:10.1144/jm.28.2.117

Abstract

Abstract. An assemblage of eleven species of Early Eocene marine intertidal and sublittoral ostracods has been found in the Crescent Formation in the Black Hills, Thurston County, Washington State, USA. The ostracods are subtropical and tropical taxa, such as Bairdoppilata, Cytherella and Neomonoceratina, which are found south of Washington today. Based on the geological age of the formation, the fauna corresponded to the Early Eocene Climatic Optimum. Five new species are recognized: Acanthocythereis olympiana sp. nov., Ambostracon irizukii sp. nov., Bairdoppilata crescentana sp. nov., Coquimba washingtonensis sp. nov. and Cytherelloidea squiresi sp. nov. This new assemblage from the Crescent Formation is the northernmost record of Early Eocene ostracods for the entire Pacific Basin.

Highlights

The Early Eocene Climatic Optimum at c. 52 Ma was the warmest of the Cenozoic global climates
There are very few reports on Early Eocene ostracods from the North Pacific Basin (e.g. Carreño & Cronin, 1993) and those from shallow-marine strata are from outcrops in California (Marianos & Valentine, 1958) and drill cores from off the East China Sea (Liu, 1989; Yang et al, 1990)
We provide the first report on shallow-water ostracods from Early Eocene marine strata of the Crescent Formation in Washington State, USA and their taxonomic characters, and data on correlating sea temperatures and water depths are discussed

Summary

INTRODUCTION

The Early Eocene Climatic Optimum at c. 52 Ma was the warmest of the Cenozoic global climates. We provide the first report on shallow-water ostracods from Early Eocene marine strata of the Crescent Formation in Washington State, USA and their taxonomic characters, and data on correlating sea temperatures and water depths are discussed. Much of the Crescent Formation was deposited during the Early Eocene Climatic Optimum and the fossils reported are the northernmost Early Eocene ostracods known from the entire North Pacific Basin (Fig. 1). Molluscan fossils of the lower Eocene informal ‘Capay’ Stage of Givens (1974) were reported (Squires & Goedert 1994, 1996; Groves & Squires, 1995) from the Crescent Formation in the Black Hills, western Washington State, from the same two sites (Fig. 1) that yielded the ostracodes studied . We regard the geological age of the Crescent Formation in the Black Hills as c. 52–50 Ma

MATERIAL AND METHODS

DISCUSSION