Richard L. Squires

Eocene deep-sea communities in localized limestones formed by subduction-related methane seeps, southwestern Washington

Densely populated communities of soft-bottom-dwelling taxa similar to those found today along subduction zones off the coasts of Japan and Oregon have been discovered in very localized deep-water limestones of late middle to late Eocene age along the southwestern margin of Washington. Subduction was prevalent in this area during this time, and compressive forces squeezed subsurface methanerich waters onto the ocean floor, where opportunistic bivalves (especially Modiolus , Calyptogena , and Thyasira ), vestimentiferan? tube worms, serpufid tube worms, siliceous sponges, very small limpets, trochid and turbinid archaeogastropods, and other macrobenthos colonized. These assemblages are the earliest recorded biologic communities formed in response to methane seeps in subduction zones.

Paleoecology of whale-fall habitats from deep-water Oligocene rocks, Olympic Peninsula, Washington state

Fossil mollusks associated with eight Oligocene whales from the Makah and Pysht Formations on the northwestern part of the Olympic Peninsula, Washington, suggest that whale carcass sulfide production supported small numbers of some chemosymbiotic invertebrates as early as 30 million years ago. Thyasirid and modiolid bivalves usually dominate these very localized molluscan assemblages; lucinid and nuculanid bivalves, scaphandrid, naticid, and buccinid gastropods are rarely present; brachiopods were found once. These fossils include, tentatively, the first fossil record for the bivalve genus Idasola, and the first record of the bivalve Thyasira peruviana Olsson, outside of probable cold-seep deposits in South America. Strata surrounding the fossil whales contain low diversity megafaunas that include rare deep-water gastropods and bivalves, large isopods, and localized cold-seep communities. The whale-fall assemblages differ significantly because of the presence of Idasola? sp. and Thyasira peruviana? and the absence of vesicomyid bivalves. Vertebrate carcasses have probably not contributed significantly to the dispersal of cold-seep and hydrothermal vent invertebrates. Seep/vent communities were well established much earlier than the evolution of cetaceans, and seep/vent invertebrates have not been found with carcasses of other large vertebrates.

NEW LATE EOCENE MOLLUSKS FROM LOCALIZED LIMESTONE DEPOSITS FORMED BY SUBDUCTION-RELATED METHANE SEEPS, SOUTHWESTERN WASHINGTON

The trochid archaeogastropod Margarites ( Pupillaria ) columbiana n. sp., the mytilid bivalve Modiolus ( Modiolus ) willapaensis n. sp., and the vesicomyid bivalve Calyptogena chinookensis n. sp. are described from the earliest known fossil communities associated with subduction-related methane seeps. The communities are in very localized limestones of late middle to late Eocene age along the southwestern margin of Washington. These limestones contain large numbers of chemosynthetic bivalves and worm tubes, as well as other macrobenthos, that colonized around cool-temperature methane seeps along the landward slopes of an ancient subduction-zone complex. Calyptogena chinookensis n. sp.is the earliest known species of this genus, which was previously known from Miocene to Recent.

Late Eocene chemosynthetic? bivalves from suspect cold seeps, Wagonwheel Mountain, central California

An anomalous pair of small, isolated calcareous sandstone bodies in the middle member of the upper Eocene Wagonwheel Formation, Wagonwheel Mountain, of the San Joaquin Valley, California, contain numerous articulated specimens of soft-bottom-dwelling bivalves. The lucinid bivalve Epilucina washingtoniana (Clark, 1925) dominates the fauna, which also sparingly contains the thyasirid bivalve Conchocele bisecta (Conrad, 1849) and the vesicomyid bivalve Vesicomya ( Vesicomya ) aff. V. (V.) tschudi Olsson, 1931. The fossils in the pair of calcareous sandstone bodies, which are surrounded by deep-water silty mudstone barren of megafossils, most likely represent cold-seep communities in the upper bathyal environment. These cold seeps apparently were formed by diffusive flow through coarse sand-fill material in submarine channels. Epilucina washingtoniana was previously known only from upper Eocene rocks on the Olympic Peninsula, Washington, and in Santa Barbara County, southern California. This species, along with a late Eocene species from Colombia, South America, are the earliest representatives of Epilucina. The Wagonwheel Formation contains one of the earliest records of Conchocele bisecta , which is a widespread Cenozoic fossil and is extant in the north Pacific. The species of Vesicomya in the Wagonwheel Formation is the earliest record of Vesicomya s.s. and has close affinity to Vescicomya (Vesicomya) tschudi Olsson, 1931, from the upper Oligocene of northwestern Peru, South America. As in the case of Conchocele bisecta, Vesicomya s.s. has not been reported previously from the Eocene of California.

Slope and Deep-Sea Fan Facies and Paleogeography of Upper Cretaceous Chatsworth Formation, Simi Hills, California

The Upper Cretaceous Chatsworth Formation is a sand-rich deep-sea fan deposit consisting of thick channelized sequences and interchannel deposits typical of middle fan facies. It has poorly developed outer fan lobes and slope facies. Petrographic and x-ray diffraction (XRD) data indicate the arkosic deposits of the Chatsworth Formation were derived from an uplifted granitic terrane. Paleocurrent studies indicate northward sediment transport and an east-trending slope. Regional comparisons of the Simi Hills with the Santa Monica and Santa Ana Mountains suggest these terranes were once contiguous and covered part of a deep-sea fan system that comprised much of the southern California area. Subsequently, these terranes have been offset along the Malibu-Cucamonga and Elsinore faults, and rotated in response to the opening of the Los Angeles basin and to other adjustments in the tectonic framework of the area. The Chatsworth Formation is thought to be part of a forearc-basin deposit similar to the Great Valley sequence and not part of the Salinian borderland block. The original geographic position of the forearc basin was to the south of the Sierra Nevada Mountains and the Great Valley sequence.

A NEW GENUS OF CRYPTIC LUCINID? BIVALVE FROM EOCENE COLD SEEPS AND TURBIDITE-INFLUENCED MUDSTONE, WESTERN WASHINGTON

LOUELLA R. SAUL, RICHARD L. SQUIRES, AND JAMES L. GOEDERT Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, Department of Geological Sciences, California State University, Northridge 91330-8266, and 15207 84th Avenue Ct. NW, Gig Harbor, Washington 98329-8765 and Museum Associate, Vertebrate Paleontology, Natural History Museum of Los Angeles County

NEW LATE CRETACEOUS GASTROPODS FROM THE PACIFIC SLOPE OF NORTH AMERICA

Abstract Two new genera and ten new species of shallow-marine, warm-water gastropods are reported from several Upper Cretaceous formations found between British Columbia and southern California. The buccinid Zaglenum new genus is represented by two new species and the turbinellid Fimbrivasum new genus is represented by three new species. The nododelphinulid Trochacanthus pacificus new species is the first record of this genus in the Western Hemisphere, and the procerthiid Nudivagus? califus new species could be the first record of this genus on the Pacific slope of North America. The xenophorid Xenophora (Endoptygma) hermax new species is only the second known Cretaceous species of this genus on the Pacific slope of North America, and this species establishes that Endoptygma Gabb, 1877, is a valid taxon. The neritid Otostoma sharonae new species is only the fourth known Cretaceous species of this genus on the Pacific slope of North America. The ringiculid Ringicula? (Ringiculopsis?) hesperiae new species is the first Campanian record of this genus on the Pacific slope of North America and the first recognition of this subgenus in this area.

Patellogastropods (Mollusca) from the Eocene Tejon Formation of southern California

Collections from the basal part of the marine Eocene Tejon Formation, Tehachapi Mountains, southern California, reveal new stratigraphic occurrences of patellogastropod limpets. Reports of these gastropods from California Paleogene strata are uncommon. The Tejon limpets are all members of the tropical genus Patelloida . Four taxa are represented in 33 specimens from five localities. These taxa include: mature specimens of P. tejonensis (Gabb, 1869), the first occurrence of the Eocene P. vokesi (Hickman, 1980) outside of Oregon, and P. triquetrus n. sp., described herein. Our study shows that a hypotype referred to P. tejonensis by Anderson and Hanna in 1925 is actually a fissurelloidean species, and we tentatively reallocate it to the genus Megathura Pilsbry, 1890. Analysis of depositional settings indicates that nearshore, shallow-subtidal depositional environments have higher patellogastropod abundance and diversity than intertidal or offshore-subtidal depositional environments. Morphological convergence between Tejon and Recent patellogastropod taxa is documented. Resemblance of the Eocene P. triquetrus n. sp. and an indeterminate Patelloidea sp. to the Quaternary “ Collisella ” scabra (Gould, 1846) and Lottia digitalis (Rathke, 1833), respectively, is remarkable.

NEW LATE CRETACEOUS (CAMPANIAN AND MAASTRICHTIAN) MARINE GASTROPODS FROM CALIFORNIA

Abstract Three new genera and six new species of shallow-marine gastropods are named from Upper Cretaceous strata found mainly in California. The trochids Cidarina cretacea new species and Cidarina beta new species, the ficid Bulbificopsis garza new genus and new species, and the cancellariid Mataxa arida new species are from the Maastrichtian part of the Moreno Formation of north-central California. This is the earliest record of Cidarina, whose previous chronologic range was middle Eocene to Recent. Bulbificopsis is the first record of a Cretaceous ficid from the Pacific slope of North America, and Mataxa was previously known only from Upper Cretaceous strata in the southeastern United States and northeastern Brazil. The buccinid Eripachya jalama new species and the fasciolariid Calkota daileyi new genus and new species are from the lower upper Campanian Jalama Formation in southern California. Calkota is also recognized herein as occurring in upper Maastrichtian strata of North Dakota and South Dakota. The new melongenid genus, Pentzia, established for Fulgur hilgardi White, 1889, is from Campanian strata throughout California; middle Campanian strata on Sucia Island, Washington; and upper Campanian to lower Maastrichtian strata in northern Baja California, Mexico.

NEW CRETACEOUS CERITHIFORM GASTROPODS FROM THE PACIFIC SLOPE OF NORTH AMERICA

Abstract Two new genera and three new species of shallow-marine, warm-water gastropods are reported from outcrops of various Cretaceous formations between British Columbia and Baja California. The potamidid Cedrosia pacifica new genus and species is from Turonian strata on Cedros Island, west coast of Baja California, Mexico. It is the earliest potamidid known from the rock record of the Pacific Slope. Alamirifica corona new genus and species, whose suprageneric relationships are uncertain, is from Turonian strata in southern California. The holotype has a round and rimmed aperture most similar to the photine buccinid Neoteron Pilsbry and Lowe, 1932. The holotype also has a pyramidal spire most similar to some fossil cerithioideans traditionally placed in the potamidid Pyrazus Montfort, 1810, but the type species of Pyrazus does not have a pyramidal spire. Future work might reveal that Alamirifica belongs to a new family. Four other Pacific Slope species are tentatively assigned to Alamirifica: the Aptian A.? harrissi (Allison, 1955); the Coniacian A.? ursa new species; the late Coniacian to early Campanian A.? harveyi (Whiteaves, 1903); and the poorly preserved Turonian Alamirifica? sp. As presently known, Cedrosia and Alamirifica were endemic to the study area, but they strongly resemble some Old World Tethyan gastropods. The distribution of A.? harveyi lends support to a relatively northern site of deposition for the Nanaimo Group.