GIANT BATHYSIPHON (ASTRORHIZINA: FORAMINIFERA) FROM THE LATE CRETACEOUS HUNTERS COVE FORMATION, SOUTHWESTERN OREGON

Abstract

ORAMINIFERANS BELONGING to the genus Bathysiphon G. O. and M. Sars in G. O. Sars, 1872 are among the largest fossil protists ever described, some species having tubular tests exceeding 100 mm in length (Miller, 1995). One species, Bathysiphon aaltoi Miller, 1986, from mid-Cretaceous fine-grained turbidites within the Franciscan Complex of northern California, may be the largest fossil foraminiferan ever collected with an estimated test length of approximately 150 mm (Miller, 1991, 1997). Species of comparable size are known from the modern deep-ocean floor (where they often rival or surpass the size of co-occurring metazoans) and are an important component of deep-sea benthic ecosystems (Gooday, 1983; Gage and Tyler, 1991; Gooday et al., 1992). In the tectonically active parts of the Pacific Rim, these giant protists are commonly found in flysch successions in association with typical deepwater trace fossils such as graphoglyptids. These remarkable tubular fossils often are the only body fossils found in abundance in Mesozoic to Cenozoic turbidite deposits in these regions, and the association appears to be indicative of deep seafloor settings strongly influenced by sedimentation and nutrient cycling from adjacent landmasses. In the regional geologic literature, however, bathysiphonids have been misidentified as body fossils of ‘‘worms’’ or as tubular trace fossils. In this report, I describe a new species of Bathysiphon from the Hunters Cove Formation, a thick sequence of Campanian‐ Maastrichtian turbidites in southwestern Oregon (Figs. 1, 2). This new taxon joins the pantheon of largest foraminiferans on record, having glassy, tubular tests up to 100 mm long and 5 mm wide. It differs from other large, Cretaceous Bathysiphon in having straight, thin-walled tests featuring vague axial striae on the outer surface. The taphonomy and paleoecology of this giant foraminiferan are briefly evaluated based on comparison with modern examples of Bathysiphon and with other Cretaceous examples from the same region. GEOLOGIC SETTING