Eocene Gastropods of Western Kamchatka Ð Implications for High-Latitude North Paci®C Biostratigraphy and Biogeography

Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 www.elsevier.nl/locate/palaeo

Eocene gastropods of western Kamchatka Ð implications for high-latitude north paci®c biostratigraphy and biogeography

A.E. Oleinik*

Department of Geography and Geology, Florida Atlantic University, 777 Glades Road, Physical Sciences Building 336, Boca Raton, FL 33431, USA Received 19 May 1999; accepted for publication 15 September 1999

Abstract Fossiliferous rocks of the Snatolskaya and Kovachinskaya formations comprise a Middle and Late Eocene shallow-marine record of the central part of western Kamchatka. Gastropod assemblages of these formations contain taxa that are conspeci®c with those in Paleogene strata of western North America and Japan, as well as a large percentage of endemic species. Analysis of the latitudinal ranges and worldwide occurrences of gastropod genera from these formations show the presence of three biogeographic components: cosmopolitan, North Paci®c, and endemic. No Tethyan, or circumtropical genera are present in these Kamchatkan Middle and Late Eocene gastropod faunas. Changes in the geographic distribution of North Paci®c gastropod assemblages through the Middle and Late Eocene indicate that only eastern Paci®c Tethyan taxa were subjected to latitudinal range reduction. The distribution of cosmopolitan and North Paci®c elements did not signi®cantly change from the Middle to Late Eocene, which suggests a relatively stable environment and climate stability during that time. High-latitude Eocene gastropod assemblages from western Kamchatka demonstrate a high level of endemism at the species level and a low-level of endemism on the genus level. This pattern is thought to be a result of the unrestricted migration of cosmopolitan taxa northward along the shallow-marine margin of the Paci®c rim. q 2001 Elsevier Science B.V. All rights reserved.

Keywords: Eocene; Kamchatka; gastropods; Tethyan; cosmopolitan; endemic; latitudinal ranges; biogeography

1. Introduction climate, and lack of roads resulted in a very incomplete knowledge of the stratigraphy and paleontology Shallow-marine rocks of Middle and Late Eocene of this area. Specimens studied for the present work age in western Kamchatka contain 86 species of were collected from 1984 to 1989 during extensive gastropods, in 53 genera. This diverse gastropod ®eld studies of the Kamchatka by expeditions of the assemblage remained very poorly studied until recent Soviet Academy of Sciences with participation of the years (Oleinik, 1987, 1988, 1994, Oleinik, 1996; author. Much of this ®eldwork was focused primarily Sinelnikova et al., 1991). Fossil collections made on the stratigraphy and paleontology along the west- prior to the 1980s by Soviet ®eld geologists mainly central coast of the Kamchatka Peninsula (the Tigil contain large and abundant bivalves (Krishtofovich, and Palana regions of local usage), adjacent to the 1947). The combination of a remote location, harsh Gulf of Shelikhov in the Sea of Okhotsk (Fig. 1). This region is characterized by a thick succession of * Fax: 11-561-2972985. Cenozoic sedimentary rocks and is known as the E-mail address: [email protected] (A.E. Oleinik). western Kamchatka Depression (Zinkevich and

Fig. 1. Geologic map of western Kamchatka with fossil localities.

Tsukanov, 1993). Paleogene marine deposits crop out and Kovachinskaya formations suggest that they in the sea cliffs along the coast of the Gulf of Sheli- were deposited at upper subtidal to outer neritic khov for a distance of approximately 500 km, as well depths (10±500 m) in the back of an active volca- as in river bluffs in the inland parts of the western nic arc (Oleinik, 1999). The existence of an active Kamchatka Depression. Middle Eocene to Miocene volcanic arc is evident from the large volume of rocks make up a large transgressive cycle, overlaying Paleogene volcanic rocks, including those of a Late Paleocene±Early Eocene hiatus that can be Middle to Late Eocene age, forming a Western traced throughout western Kamchatka and the Sea Kamchatka Volcanic Belt, also known as the of Okhotsk region (Gladenkov et al., 1990). Middle Koryak±West Kamchatka Volcanic Belt (Zonenshain Eocene strata overlie Paleocene±Lower Eocene rocks et al., 1990). Based on the K±Ar dating of the with angular unconformity and are conformably volcanic rocks, the last episode of Paleogene overlain by the Uppermost Eocene±Lower Oligo- volcanism within the Western Kamchatka Volcanic cene Amaninskaya and Gakhinskaya formations Belt occurred during the uppermost Bartonian± (Gladenkov et al., 1991). The lithology, tectonic lowermost Priabonian (46.5±37.4 my) (Gladenkov et history, and faunal composition of the Snatolskaya al., 1990). A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 123 2. Area description, materials and methods: Formation in the Mainach River Section contain stratigraphy, age, and correlation of Middle and Rhizammina indivisa, Bathysiphon nodosariaformis, Upper Eocene rocks of western Kamchatka Silicosigmolinacf. californica, Haplophragmoides glabratus, Asanospira cf. exavata, Asanospira cf. Fossiliferous Eocene shallow-marine rocks crop akkeshiensis, Glomospira corona,andRecurvoides sp. out in sea-cliffs and river bluffs along the western The upper part of the Snatolskaya Formation in the coast of Kamchatka. They are subdivided into the southern ¯ank of the Tochilinskiy Section contains Snatolskaya and Kovachinskaya formations that Trochammina vitrea, Gyroidina kamtschatica, comprise the basal part of a large transgressive Elphidium californicum, Reophax dif¯ugiformis, cycle, and are separated from the older Paleogene Haplopharagmoides snatolensis, Cyclammina ezoensis, rocks by a regional unconformity (Gladenkov et al., Trochammina markini, Cyclammina tani, Dorothia 1991). amakusaensis, Textularia imariensis, Guttulina irregu- The most complete sections of the Snatolskaya and laris, Gyroidina kamtschatica, Elphidium asagiensis, Kovachinskaya formations in the Tigil and Palana Caucasina eocaenica kamtschatica, Globobulimina regions crop out in the sea cliffs along the southeast- paci®ca,andBolivina jacksonensis (Gladenkov et al., ern coast of the Gulf of Shelikhov. This area is char- 1991b). These assemblages strongly imply a Middle acterized by the Tigil and Lesnaya±Palana uplifts of Eocene age for the Snatolskaya Formation (Gladenkov Neogene age, which produced a number of synclines et al., 1991a). Serova (1969), however, noted on the and anticlines of predominantly northeastern strike possible presence of the Upper Eocene rocks within that are incised by a shoreline running generally this formation. The planktonic foraminiferal assem- perpendicular to strike. Poor exposures adjacent to blage is poorly preserved and can be generally assigned the seashore and inland areas necessitated making a to the Globigerina boweri regional zone (Serova, 1969; composite section from numerous outcrops in river Krasheninnikov et al., 1988) and suggests a Lutetian to valleys. Nineteen stratigraphic sections of the Bartonian age for the Snatolskaya Formation. A number Snatolskaya and Kovachinskaya formations, ranging of conspeci®c benthic and planktonic foraminifers in the in thickness from 40 to nearly 800 m, were measured Snatolskaya Formation of western Kamchatka suggest at 16 localities in Tigil and Palana regions of western correlations with the Narizian Stage of California Kamchatka (Fig. 1). (Mallory, 1959), the Middle Eocene (Lutetian± The Snatolskaya Formation is represented mostly Bartonian) Takisawa Formation (Honshu), and the by shallow-marine, medium- to ®ne-grained, laterally lowermost part of the Poronai Formation (Upper continuous sandstones, with abundant lagoonal and Bartonian, Hokkaido) of Japan, which contain both delta front deposits, containing a rich and diverse benthic foraminiferal assemblages and nannoplankton fauna of benthic molluscs. Only its lowermost part (Saito et al., 1984). locally contains alluvial conglomerates and terrestrial The Kovachinskaya Formation conformably over- near-shore deposits, where the Snatolskaya Formation lies the Snatolskaya Formation and consists of marine directly overlay Cretaceous rocks. The thickness of siltstone, claystone, and sandstone. Rocks of the the Snatolskaya Formation in the Tigil and Palana Kovachinskaya Formation contain numerous tuff regions (a continuous and complete section with horizons, which suggest an increase in volcanic activ- observable lower and upper contacts) varies from 10 ity during its deposition. The Kovachinskaya Forma- to 295 m. Rocks of the Snatolskaya Formation tion in the Tigil and Palana regions varies in thickness become thinner and coarser-grained, and change from 30 to 475 m and is conformably overlain by from ®ne-grained sandstones to medium- to coarse- Lower Oligocene rocks of the Amaninskya and grained sandstones and conglomerates, toward the Gakhinskaya formations. areas of exposure of Cretaceous rocks. The Kovachinskaya Formation consists of a ®ne- Benthic foraminifers in the Snatolskaya Formation grained clayey rocks, and reaches its maximum thick- occur at two localities in the Tigil Region: the ness in areas most distant from outcrops of Cretaceous Tochilinskaya Anticline and Mainach River sections rocks. Rocks of this formation become progressively (Fig. 1). The lower and middle parts of the Snatolskaya enriched in coarser-grained clastics toward the 124 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 125 Cretaceous outcrops, where it reaches its minimal laria packardi packardi, P. packardi multilineata, thickness and consists mostly of sandstone and Caucasina eocaenica kamtschatica, C. schwageri, conglomerate. Uvigerina garzaensis nudorobusta, Bulimina corru- Because of its open-marine deposition, the gata, B. sculptilis, and Anomalina californiensis Kovachinskaya Formation contains more abundant (Serova, 1985). The foraminiferal assemblage charac- and diverse foraminiferal assemblages than does the teristic of the Kovachinskaya Formation also occurs Snatolskaya Formation. Plectofrondicularia packardi in the eastern Kamchatka, Japan and western North packardi, Alabamina californica, and Globocassidu- America (Serova, 1985). Fotyanova and Serova lina globosa among the most abundant forms of (1976) referred the Kovachinskaya Formation to the benthic foraminifers in the Kovachinskaya Formation Bulimina corrugata zone. Bulimina corrugata co- on the southern ¯ank of the Tochilinskiy Section. The occurs with Globigerina frontosa in the Ilpinskiy Kovachinskaya Formation also contains a diverse Peninsula of northeastern Kamchatka. The Globiger- assemblage that is commonly found in most sections ina frontosa zone of the Ilpinskiy Peninsula, as well as of the Tigil and Palana regions: Gyrodina condoni, the Bulimina corrugata zone in California, is correla- Bulimina debilis, Bathysiphon eocenicus, Ammodis- tive with the P14 zone of the standard planktonic cus pennyi, Haplophragmoides obliquicameratus, foraminiferal sequence and indicates a Bartonian Budashevaella deserta, Cyclammina cushmani, C. age (Krasheninnikov et al., 1988; Volobueva et al., paci®ca, Ammobaculites kamtschaticus, A. akabir- 1994). This correlation is also supported by the co- oensis, Ammomarginulina stephensoni, Robulus inor- occurrence of Globigerina frontosa with calcareous natus, R. alatolimbatus, Dentalina plamerae, nannoplankton in the Ilpinskiy Peninsula, indicative Alabamina californica, Cibicides pachecoensis, C. of the NP17 zone of Martini (1971) and the CP14 zone beckii, Nonion durchani, N. sorachiense, Melonis of Bukry (1973) and Bukry (1975), which suggests a planatum, Bulimina debilis, and Globobulimina late Bartonian age for at least the basal beds of the paci®ca. In addition to these taxa mentioned above, Kovachinskaya Formation. Similar foraminiferal the Kovachinskaya Formation in the Mainach assemblages in western North America, containing Section, also contains Rhabdammina eocenica, Bulimina sculptilis, Plectofrondicularia packardi, Reophax tappuensis, R. dentaliniformis, Ammodiscus Uvegerina atwili, and Cyclammina clarki, have been concinnus, Haplopharagmoides aff. laminatus, H. cf. assigned to the Refugian Stage (Serova, 1985; spadix, H. subimpressus, Budashevaella ex gr. Krasheninnikov et al., 1988). Nannoplankton deserta, Guttulina irregularis, G. problema, biochronozone NP20 within the Refugian Stage Globulina gibba, G. landesi, Gyrodina condoni, further suggests a Priabonian age for a large part Cibiscides metastersi, C. pachecoensis, C. becki, C. of the Kovachinskaya Formation. Analogs of the eponidiformis, Melonis shimokinense, Epistominella Kovachinskaya Formation foraminiferal assem- minuta, Caucasina eocenica kamtschatica, C. cf. blage in Japan are found in the Okinoshiman schwageri, Trifarina advena californica, Bolivina Stage (Kyushu), which is dated as late Middle to kleinpelli, B. jacksonensis, and Globobulimina debilis Late Eocene based on the planktonic foraminifers, (Gladenkov et al., 1991b). and which contains a diverse benthic assemblage According to Serova (1985), the foraminiferal (50 species and subspecies) of the Plectofrondicu- assemblage of the Kovachinskaya Formation of the laria packardi±Bulimina ezoensis zone. This zone Tochilinskiy Section contains over 150 species, is also found in the upper part of the Poronai mostly benthic foraminifers. Planktonic taxa are rare Formation of Hokkaido, where it is known as and represented only by species of Globigerina. The the P. packardi±B. schwagerior B. schwageri± most commonly found species in this assemblage are: Gyrodina yokoyamai zone (Gladenkov et al., Gyroidina condoni, Cibicides hodgei, Plectofrondicu- 1991) (Fig. 2).

Fig. 2. Correlation of the Snatolskaya and Kovachinskaya formations with Eocene formations of western North America and Japan, U.S. West Coast Eocene molluscan stages (after Saul, 1983; Squires, 1984; Prothero and Armentrout, 1985; Berggren and Prothero, 1992; Nesbitt, 1995), standard ages, planktonic foraminiferal zones, and nannoplankton zones after Berggren et al. (1995). 126 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140

Fig. 3. Stratigraphic distribution of species ranging through the Snatolskaya and Kovachinskaya formations.

3. Results and analyses: biostratigraphy and leaching have been observed in both the Snatolskaya gastropod fauna of the Snatolskaya and and Kovachinskaya formations at the Uvuch Kovachinskaya formations Mountain and Moroshka River localities (Fig. 1). Thus, the breakage and abrasion of shells was caused Gastropod shells are moderately common in the by diagenetic processes and not by reworking. Snatolskaya and Kovachinskaya formations, but differ The Snatolskaya Formation contains a molluscan in preservation from locality to locality. The best assemblage recognizable over a large area of western preserved specimens (without signs of post-mortem Kamchatka. Gastropods occur in all sections of the wear or secondary leaching of the shell material) Snatolskaya Formation. The biostratigraphic zonation occur in a ®ne-grained sandstone of the lower member proposed herein for the Snatolskaya Formation is of the Snatolskaya Formation, particularly at the based on the ®rst appearance of characteristic taxa, Snatol River locality (Fig. 1), or from hard carbonate in addition totaxa restricted to a particular interval. concretions that are scattered throughout the Eocene Special consideration was given to a continuity, or section at numerous localities. Well-preserved speci- lateral stability of molluscan assemblages. mens typically have intact protoconchs and delicate The individual stratigraphic ranges of 78 species ornamentation patterns. The dissolution and decorti- and 53 genera of gastropods in the Snatolskaya and cation of shell material occur rapidly when specimens Kovachinskaya formations, plotted by each individual become exposed to weathering. Some traces of shell measured section and locality in the studied region are A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 127

Fig. 4. Ranges of stratigraphically restricted species in the Snatolskaya and Kovachinskaya formations. 128 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140

Fig. 5. Percentages and numbers (at the end of each bar) of genera and species present in the Snatolskaya and Kovachinskaya formations. given in Figs. 3 and 4. Local molluscan units proposed whereas 14 species (17.9%) and seven genera (13.2%) in the present paper are based on temporal changes in range throughout both members (Fig. 5). There are the local stratigraphic ranges of gastropod species. only two species that range from the underlying Fifty-three species and 34 genera occur in the Napanskaya Formation (Gladenkov et al., 1997) into Snatolskaya Formation and 36 species and 32 genera, the overlying Snatolskaya Formation. One of them is in the Kovachinskaya Formation. Calyptraea diegoana, which ranges through the These two distinct, successive gastropod assem- Snatolskaya into the Kovachinskaya Formation, and blages de®ne the Lower and Upper Snatolskaya the other is the Kamchatkan species Polinices (Poli- Formation (Figs. 3 and 4), as used in this paper. The nices) snatolensis, which is morphologically similar Lower Member contains 47 species and 23 genera of to the wide-ranging Polinices (Euspira) nuciformis gastropods. These two members do not necessarily and Polinices (Euspira) hotsoni of western North correspond to lithologic changes within the forma- America. tions, but are based on a faunal assemblage that can A two-part subdivision of the Snatolskaya Forma- be recognized in the great majority of Snatolskaya tion has been proposed earlier, based on the entire Formation sections in western Kamchatka. Twenty- molluscan assemblage, known at that time, including four species and 11 genera are restricted to the many bivalves (Krishtofovich, 1947; Dyakov, 1957). Lower Member, and four species and two genera to Author's data on gastropod distribution do not support the Upper Member of the Snatolskaya Formation. The the subdivision of the Snatolskaya Formation into Lower and Upper members share 23 species and 19 three `layers with molluscs', proposed by Gladenkov genera, which suggests a strong facies- and climate- et al. (1991). For example, the Plicacesta sameshi- related similarity. The relatively uniform lithologic mai±Solen tigilensis layer of Gladenkov et al. composition and similar molluscan assemblages (1991) was more or less clearly de®ned only in the throughout the formation suggest uniform deposi- Pyatibratka River locality, and cannot be traced in tional and ecologic environments and stable climatic other sections in western Kamchatka. Molluscan conditions. The coef®cient of community (Jaccard, layers named for a particular taxon (or taxa) by 1901) between the lower and upper members of the Gladenkov et al. (1991), following the practice usual Snatolskaya Formation is 0.45 at the species level and for microfossil zones is inappropriate because most 0.59 at the genus level. Twenty-four species (30.8% of taxa used in these names are not restricted, or even the 78 total species) and 11 genera (20.7% of the 53 most abundant, in their nominate. total genera) disappear at the Lower and Upper The Kovachinskaya Formation contains a gastro- Snatolskaya Formation boundary, six species (7.7%) pod assemblage that is distinctively different from and three genera (5.7%) appear at the same boundary, those of the Lower and Upper Snatolskaya Formation. A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 129 The Kovachinskaya fauna re¯ects deeper water and ranges from the Late Paleocene through generally softer substrates than the Snatolskaya fauna. `Tejon,' in Washington, Oregon, and California Twenty-®ve species (32%) and 18 genera (34%) are (Marincovich, 1977; Squires, 1987). known only in a single member within the Kovachins- Scaphander (Mirascapha) costatus (Gabb, 1864) kaya Formation (Fig. 4). Two species (2.6%) and one ranges from the `Martinez' to `Transition' stages genus (1.9%) also occur in the Upper Snatolskaya (Late Paleocene±Middle Eocene) of California Formation. Eighteen species (23%) and 10 genera Oregon, and western Washington (Squires, (18.9%) disappear, and 25 species (32%) and 18 1984). genera (34%), ®rst appear at the boundary between Kovachinskaya Formation (Late Eocene of the Snatolskaya and Kovachinskaya formations (Fig. Kamchatka). 5). These numbers suggest that a larger faunal turn- Hataiella (Kotakiella) poronaiensis (Takeda, over occurred at the Snatolskaya/Kovachinskaya 1953) ranges from the Late Eocene through boundary than at the Lower/Upper Snatolskaya early Late Oligocene in Japan (Poronai (Middle Formation boundary. The Jaccard coef®cients calcu- to Late Eocene), Momijiyama (Late Eocene± lated for the total number of gastropod genera and Early Oligocene), Omagari, Shitakara, Charo, species in the Snatolskaya and Kovachinskaya forma- and Nuibetsu formations (Early to Late tions are 0.14 for species and 0.25 for genera, which Oligocene)) (Honda, 1989; Sinelnikova et al., are signi®cantly lower than coef®cients for the 1991; Titova, 1994). Snatolskaya Formation. These coef®cients clearly Trominina dispar (Takeda, 1953) is also reported indicate that gastropod assemblages of the from the latest Eocene±early Oligocene of Snatolskaya and Kovachinskaya formations are less Sakhalin (Takaradai Formation) (Takeda, 1953) similar, than assemblages of the Lower and Upper and Early Oligocene (Charo and Nuibetsu Snatolskaya Formation. Formations) of Hokkaido (Gladenkov et al., Thirteen species in the Snatolskaya Formation and 1988; Honda, 1989; Titova, 1994). six species in the Kovachinskaya Formation are conspeci®c with taxa of the western coast of North America and Japan. Comparison of published 3.2. Heterochronous species stratigraphic ranges of these species in the western North America and Japan with the stratigraphic Lower member of the Snatolskaya Formation (Late ranges in Kamchatka suggest three main categories Middle Eocene of Kamchatka). of conspeci®c species for the North Paci®c. Ficopsis meganosensis (Clark and Woodford, 1927). Known occurrences are in the upper part 3.1. Species with wide stratigraphic ranges of the `Meganos' stage (Clark and Vokes, 1936), most probably ranging from Late Paleocene to Early Eocene (Weaver, 1942). Lower member of the Snatolskaya Formation (Late Polinices (Euspira) lincolnensis (Weaver, 1916) Middle Eocene of Kamchatka). ranges from Late Eocene to Late Miocene in Calyptraea diegoana Conrad, 1855 occurs in the Oregon, Washington and Vancouver Island Late Paleocene through Late Oligocene of (British Columbia) (Marincovich, 1977). Washington, Oregon, and California (Squires, Scaphander (Mirascapha) alaskensis Clark, 1987, 1988). 1932 is also known from the Early to Late Olivella matchewsonii umpquaensis Turner, Oligocene parts of Poul Creek and Yakataga 1938 ranges from the `Martinez' to `Tejon' formations of southern Alaska (Clark, 1932; molluscan stages of California, and from the Kanno, 1971). Late Paleocene through Late Eocene in Turriola tokunagai (Yokoyama, 1924) also Washington, Oregon, and California (Turner, occurs in the Early to Late Oligocene of the 1938; Squires, 1984). northwestern Paci®c: the Ombetsu Group of Polinices (Euspira) nuciformis Gabb, 1864 Hokkaido (Honda, 1989; Sinelnikova et al., 130 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 1991; Titova, 1994) and Arakai Formation of are considered to be age-diagnostic for the Sakhalin (Titova, 1994). Snatolskaya and Kovachinskaya formations and Exilia bentsonae Hickman, 1980 occurs in the useful for biostratigraphic correlation. Late Eocene Keasey Formation of northwestern Oregon (Hickman, 1980). Upper Member of the Snatolskaya Formation 4. Eocene paleogeography and paleocirculation of (Middle Eocene of Kamchatka). the North Paci®c Ancilla (Spirancilla) gabbiCossmann, 1899 occurs in the `Domengine' Stage of California The origin and distribution of Eocene faunas in the which is of Early to early Middle Eocene age northern Paci®c cannot be well understood without (Vokes, 1939; Squires, 1984) insights into the general paleogeography of the Paci®c Kovachinskaya Formation (Late Eocene of rim and the inferred patterns of paleocirculation. Kamchatka). During the Eocene, the shorelines, total area, and Margarites (Pupillaria) ef®ngeri (Durham, bathymetry of the Paci®c Ocean were quite different 1944) occurs in the Echinophoria fax zone of from those existing today. One of the major paleogeo- the Lincoln Creek Formation (Early Oligocene, graphic elements in the northern part of the Paci®c Washington) (Weaver, 1942; Prothero and Ocean was the Bering Land Bridge, also known in Armentrout, 1985) the literature as `Beringia', which connected Eurasia Colus (Aulacofusus) asagaensisMakiyama, and North America throughout most of the early and 1934, occurs in the Lower Oligocene Asagai middle Tertiary (Durham, 1967; Hopkins, 1967). Formation of Kyushu and in the Matschigar There are no reliable data to suggest the existence of and Arakai formations of the Sakhalin Island a `paleo-Bering Strait' during the Paleogene (Marin- (Oyama et al., 1960; Gladenkov et al., 1988). covich and Gladenkov, 1999). The similarity of land mammals and plants suggests more or less unhindered terrestrial migration between the Old and New Worlds 3.3. Species with narrow stratigraphic ranges (Wolfe and Hopkins, 1967). The record of marine molluscs clearly indicates an absence of faunal inter- Lower Member of the Snatolskaya Formation (Late change between the Paci®c and Arctic basins during Middle Eocene of Kamchatka). the Paleogene (Scarlato and Kafanov, 1976; Kafanov, Fusinus (Fusinus) willisi (Dickerson, 1915) from 1979; Marincovich, 1993). The western part of the the Cowlitz Formation (late Middle Eocene), Beringian platform apparently extended up to the southwestern Washington (Weaver, 1942; Koryak Upland and eastern Kamchatka (Asano, Nesbitt, 1995). 1963; Shantser, 1974; Vdovin, 1976). Paleogene Odostomia (Doliella) hiltoni (Van Winkle, 1918) unconformities recorded in seismic data at the western from the Cowlitz Formation (late Middle part o the Bering Sea (Goryachev, 1965) suggest the Eocene), southwestern Washington (Weaver, existence of large areas of dry land from the Late 1942; Nesbitt, 1995). Cretaceous (Maastrichtian) through Middle Eocene. Kovachinskaya Formation (Late Eocene of Some authors suggest that extensive dry land existed Kamchatka). at the present-day location of the Sea of Okhotsk and Turricula keaseyensis Hickman, 1976, from the the Sea of Japan (Asano, 1963; Alexandrov, 1973; Late Eocene Keasey Formation of northwestern Shantser, 1974; Sergeev, 1976). Oregon (Hickman, 1980). Relatively small sedimentary basins, with normal Neptunea altispirata (Nagao, 1928) from the marine to restricted circulation, existed in the areas of Late Eocene Doshi Formation of northern modern Sakhalin and Hokkaido (Iijima, 1964; Kyushu (Oyama et al., 1960; Gladenkov et al., Zhidkova et al., 1974; Matsumoto, 1964; Honda, 1988; Sinelnikova et al., 1991). 1991). The Kamchatka was represented by an island archipelago, which consisted of islands of various size Based on the species cited above, the last four species and formed a volcanic arc. The distribution of A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 131

Fig. 6. Eocene paleogeography, inferred circulation, and distribution of the major biogeographic groups of gastropods in the North Paci®c. shallow-marine deposits and invertebrate faunas pattern similar to the modern one in the North Paci®c, along the western coast of North America suggests with an anticyclonic subtropical gyre and a cyclonic a continuous shallow-marine habitat extending subarctic gyre as the main features (Kennett, 1982) from northern Mexico to Alaska (Snavely and (Fig. 6). However, the latitudinal extent and intensity Wagner, 1963; Nilsen and McKee, 1979). This of North Paci®c oceanic circulation during Paleogene, North±South coastline provided a submeridional especially local shallow-water patterns, are still dispersal route for shallow-marine molluscs during poorly understood. the Paleogene (Fig. 6). The circulation of the world ocean in the Eocene was dominated by the westward-¯owing, circumtro- 5. Discussion: gastropod faunas and biogeography pical Tethys Current, which resulted in the widespread dispersal and largely cosmopolitan nature of The gastropod fauna of Kamchatka, except for a Paleogene marine faunas (Davies, 1971). The exact few specimens from Alaska (Marincovich, 1988), is position of seaways connecting the Atlantic and the northernmost record of Paleogene molluscs in the Paci®c oceans during the Paleocene and Eocene is North Paci®c. Two biogeographic components of not known, and a summary of the Eocene Atlantic± Eocene faunas have previously been identi®ed in Paci®c connection is given in Squires (1987). The lower latitudes of the western and eastern North main evidence for a marine connection between the Paci®c (the western coast of North America and Atlantic and Paci®c is the presence of many Old Japan), a Tethyan or Tethyan±Indo-Paci®c element World Tethyan taxa in Eocene faunas of western and a northern Paci®c element (Oyama et al., 1960; North America, particularly California. Some species Hickman, 1980; Squires, 1984; Squires and are strikingly similar to those occurring in Europe and Demetrion, 1992; Honda, 1991; Honda, 1994). The Africa (Squires, 1984, 1987). Circulation since the Tethyan (Tethyan±Indo-Paci®c) element included Paleocene outside of the equatorial northern Paci®c, genera of presumed warm-water af®nities with a has been well documented in recent years. It had a circumtropical distribution. These genera were 132 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140

Table 1 Worldwide occurrences of gastropod genera present in the Snatolskaya and Kovachinskaya formations. Asterisks next to genus name indicate taxa found only in the North Paci®c region (Kamchatka, Sakhalin, Japan, and West Coast of North America). North Paci®c occurrences are excluded. Worldwide data from Davies (1971) and Wenz (1933±1944). European data from: Bellardi (1872±1888), Cossmann and Pissarro (1910±1913), Cossmann (1895±1925), Edwards (1849), Furon and Soyer (1947), and Klyushnikov (1958) North American data (excluding the West Coast) from Garvie (1996), Dockery (1977), McNeil and Dockery (1984), Richards and Palmer (1953), Toumlin (1977), Palmer (1937), Palmer and Brann (1965±1966) and Gardner (1923, 1927, 1939) South American data from Steimann and Wilckens (1908), Woods et al. (1922), Von Ihering (1905±1907) and Zinsmeister (1981) African data from Newton (1922) and Eames (1957). Asian data (excluding Sakhalin and Japan) from Alexeev (1963), Ilyina (1955), Eames (1952), Shuto (1980, 1984), Vredenburg (1923a, 1923b, 1928), Douville (1928) and Cox (1930). Australian data from Long (1981). New Zealand data from Beu and Maxwell (1990), Marwick (1931), Maxwell (1992) and Powell (1942). Antarctic data from Wilckens (1911, 1924), Stilwell and Zinsmeister (1992) and Zinsmeister and Camacho (1982)

Genus Europe North America South America Africa Asia Australia New Zealand Antarctica

Acmaea s. l. £££ Acteon ££ £££ £ Ancilla ££ £ £ Antimelatomap Apiotoma ££ £ ££ Beringiusp Bonellitia ££££ Calyptraea ££ £ £££ Cancellaria ££ £ Clivoluturrisp Colusp Comitas £ Conominolia ££ Conus ££ £ ££££ Creonellap Crepidula ££ ££ Diodora ££ £ Epitonium s. l. ££ £ ££££ £ Exilia ££ £ Ficopsis £ Ficus ££ £ £ £ Fulgorariap Fusinus ££ £ ££ £ Gibbula £ Hataiellap Homalopoma ££ Lirosoma £ ? Lishkeiap Makiyamaia £ Margaritesp Marshallena ££ Mipusp Molopophorusp Nekewisp Neptuneap Nihoniap Notoacmaeap Odostomia ££££ Olivella ££ Polinices ££ £ ££££ Problacmaeap Pseudoliomesusp Puncturellap A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 133

Table 1 (continued)

Genus Europe North America South America Africa Asia Australia New Zealand Antarctica

Scaphander ££ £££ £ Siphonalia ££ £ Snatoliap Solariella ££ £ Tromininap Turciculap Turricula ££££ Turrinosyrinxp Turriolap ranging south of 508N in the Eocene. The northern (21.9%), ®ve (21.7%), and 11 (34.4%) genera in the Paci®c element was represented by genera that were Lower Snatolskaya, Upper Snatolskaya, and Kova- widespread in the high and mid-latitude North Paci®c chinskaya formations, respectively. The endemic in the Paleogene, including central to northern Japan, component remained stable at four to ®ve species, Sakhalin, Kamchatka, Alaska, Washington, Oregon, which corresponded to 15.6% of the Lower and California. The majority of these genera are still Snatolskaya, 17.4% of the Upper Snatolskaya, and living in the northern Paci®c today. Some northern 12.5% of the Kovachinskaya Formation faunas (Fig. Paci®c genera penetrated into the subtropical Paci®c 8). The in¯uence of the eastern and western Paci®c Ocean, but did not attain circumtropical distribution faunas on Kamchatka can be evaluated by tallying the within the Tethyan (sensu Kauffman, 1973; Sohl, number of species in common with Eocene of western 1987) realm. The worldwide occurrences of gastropod North America and Japan. The Lower Snatolskaya genera recorded from the Eocene of Kamchatka (Table Formation contains 11 species (23.4%), the Upper 1) and their latitudinal ranges in the high-latitude North Snatolskaya has eight species (27.6%), and the Paci®c (Fig. 7), suggest that Kamchatkan gastropod Kovachinskaya Formation has six species (16.6%) assemblages were largely composed of cosmopolitan that also occur in western North America (Fig. 8). genera. The high percentage of cosmopolitan taxa in Four such species: Calyptraea diegoana, Crepidula the Eocene faunas was a product of low latitudinal pileum, Odostomia (Doliella) hiltoni, and Scaphander temperature gradients (Addicott, 1970) that allowed (Mirascapha) alaskensis, range throughout the warm-water taxa to dwell in high latitudes. Snatolskaya and Kovachinskaya formations. In Taxa with at least one occurrence outside of both addition, Ficopsis meganosensis, Fusinus (Fusinus) the North Paci®c and the Tethyan (tropical) realms willisi, Polinices (Euspira) nuciformis, and Scaphan- (Table 1) are here considered to be cosmopolitan. der (Mirascapha) costatus occur only in the Lower Genera found only in the Eocene of Kamchatka are member of the Snatolskaya Formation, while Exilia considered to be endemic. Genera that occur else- bentsonae, Olivella matchewsonii umpquaensis, and where in the North Paci®c realm are cited as North Polinices (Euspira) lincolnensis occur in both the Paci®c elements (Fig. 7). No Tethyan genera have Lower and Upper Snatolskaya Formation, and been found in Middle or Upper Eocene rocks of Margarites (Pupillaria) ef®ngeri and Turricula Kamchatka. keaseyensis occur in the Kovachinskaya Formation. The cosmopolitan element remained high through- Only one species known in Japan, Turriola tokunagai, out the Middle Eocene, with 20 genera (62.5%) in the occurs in the Lower and Upper Snatolskaya Forma- Lower Snatolskaya and 14 genera (60.9%) in the tion, and also ranges into the Kovachinskaya Forma- Upper Snatolskaya Formation, but declined to 17 tion. The Kovachinskaya Formation contains four genera (53.1%) in the Upper Eocene Kovachinskaya species that also occur in the Paleogene of Japan Formation. This decline was accompanied by an and Sakhalin: Colus (Aulacofusus) asagaensis, Tromi- increase of the North Paci®c component, with seven nina dispar, Hataiella (Kotakiella) poronaiensis, and 134 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 Neptunea altispirata. All of these species belong to the North Paci®c biogeographic component (Figs. 7 and 8). This pattern of decreasing numbers of eastern Paci®c and increasing numbers of western Paci®c species may indicate a weaker eastern Paci®c in¯u- ence on high-latitude northern Paci®c faunas towards the end of the Eocene. However, this pattern may result, at least partly, from a poor preservation and incomplete knowledge of the Middle Eocene faunas of Japan. Temporal changes in the geographic distribution of characteristic gastropod assemblages in the northern Paci®c, from Middle to Late Eocene (Fig. 9), clearly indicate a latitudinal range reduction for Tethyan genera, particularly in the eastern Paci®c. Tethyan genera that had dwelled in the northeastern Paci®c as far North as western Washington during the middle Eocene, become restricted to southern California during the Late Eocene. The latitudinal ranges of Tethyan genera in the western North Paci®c remained the same, being con®ned in their northernmost pene- tration to Kyushu, in the Taiwan±South Japan Province of Honda (1991, 1994). There was no signif- icant change in the latitudinal ranges of cosmopolitan or North Paci®c genera from the Middle to Late Eocene (Fig. 9). This pattern suggests that high latitudes were not severely affected by global climate changes, at least during the Late Eocene. On the other hand, minor changes in global climate and/or circulation patterns may have limited the latitudinal migration of the more temperature-sensitive circum- equatorial genera, into the northern high latitudes. There are few quantitative data on which to base speculation about high-latitude Eocene biotic provinces in the North Paci®c. Provinces can be recognized on the basis of their unique taxonomic compositions. Such taxa are commonly species, but

Fig. 7. Latitudinal ranges of gastropod genera of the Snatolskaya and Kovachinskaya formations in the northern Paci®c. Latitudinal range data from museum specimens and the following literature sources: Anderson and Hanna, 1925; Clark, 1938; Clark and Ander- son, 1938; Devjatilova and Volobueva, 1981; Dickerson, 1914, 1915, 1916; Hanna, 1927; Hickman, 1976, 1980; Honda, 1991, Honda, 1994; Krishtofovich and Ilyina, 1954; Marincovich, 1977; Oyama et al., 1960; Squires, 1984, 1985, 1987, 1988; Squires and Goedert, 1994; Squires and Groves, 1992; Squires et al., 1992; Turner, 1938; Vokes, 1939; Weaver, 1916, 1942. A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 135

Fig. 8. Diversity and changes in the biogeographic composition of gastropod assemblages in the Snatolskaya and Kovachinskaya formations.

Fig. 9. Temporal changes in the latitudinal ranges of characteristic Eocene gastropod assemblages in the northern Paci®c. An asterisk next to the genus name indicates that the record for the genus is probably incomplete. 136 A.E. Oleinik / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 121±140 may be higher taxa, and it is common for paleontolo- this study and for numerous stimulating discussions. gists to use genera in reconstructing provincial The author would also like to extend his deep grati- boundaries. Biogeographic patterns de®ned at the tude to Richard Squires of California State University species-level can also sometimes be recognized at at Northridge, for sharing a wealth of information on the genus- and family-levels (Campbell and Valentine, Eocene faunas of the US. West Coast and for his 1977; Smith, 1989). One of the most frequently insightful comments on this study. Special thanks to quoted rules that have been used to identify provincial Louie Marincovich of California Academy of regions is that at least one-half of the species living in Sciences and David T. Dockery III of the Mississippi the region must be endemic. However, there is no Department of Environmental Quality, Of®ce of special reason to employ any particular arbitrary Geology, for a very helpful comments and critical level of endemism to de®ne a province. The generic review of the early version of the manuscript. level of endemism which can be considered satisfac- tory to de®ne a province, have to be lower than the species level by the virtue of higher taxonomic rank. References Kauffman (1973) assigned a 10±25% of endemic genera for a subprovince, 25±50% for a province, Addicott, W.O., 1970. Latitudinal gradients in Tertiary molluscan faunas of the Paci®c Coast. Palaeogeography, Palaeoclimatol- and 50±75% for a regions. These numbers were ogy, Palaeoecology 8, 287±312. proposed based on study of distribution of Cretaceous Alexandrov, S.M., 1973. [in Russian]. Sakhalin Island. Nauka, bivalves is not universally accepted for all ages and Moscow (pp. 1±183). other groups of organisms. Alexeev, A.K., 1963. Paleogene Fauna of the northern Sea of Taking into account the warm and equable climatic Aral region. Academy of Sciences of Armenia, Erevan, pp 1±229 [in Russian]. conditions, and the linearity of shallow-marine Anderson, F.M., Hanna, G.D., 1925. Fauna and stratigraphic rela- habitats around the North Paci®c rim in the Paleogene tions of the Tejon Eocene at the type locality in Kern County, (Fig. 6). Endemism at the genus-level may have been California. California Academy of Sciences Occasional Papers low, while species-level endemism could still have 11, 1±249. been high, owing to local conditions. This pattern of Asano, K., 1963. The Paleogene. In: Takai, F., Matsumoto, T., Toriyama, R. (Eds.), Geology of Japan. University of California high species-level endemism is present in the Middle Press, pp. 129±140. and Late Eocene gastropod fauna of the western Bellardi, L., 1872±1888. I Molluschi dei terreni terziarii del Kamchatka, ranged from highs of 65.5% in the Piemonte e della Liguria. Memorie della (Reale) Accademia Upper Snatolskaya and 72.3% in the Lower delle Scienze, Torino, Parts 1±5, pp. 1±364. Snatolskaya Formation, to lows in genus-level Berggren, W.A., Prothero, D.R., 1992. Eocene±Oligocene climatic and biotic evolution: an overview. In: Prothero, D.R., Berggren, endemism of 12.5% in the Kovachinskaya and W.A. (Eds.). Eocene±Oligocene Climatic and Biotic Evolution. 17.4% in the Upper Snatolskaya Formation. It is Princeton University Press, Princeton, pp. 1±28. possible to propose a separate high-latitude province Berggren, W.A., Kent, D.V., Swisher III, C.C., Aubry, M.-P., 1995. in the northwestern Paci®c, using a species-level A revised Cenozoic geochronology and chronostratigraphy. In: gastropod data, but matter becomes questionable Berggren, W.A., Kent, D.V., Aubry, M.-P., Hardenbol, J. (Eds.), Geochronology, Time Scales and Global Stratigraphic when based on genus-level data. High latitude North Correlation. SEPM Special Publication, vol. 54, pp. 129±212. Paci®c biogeography and the extent of Paleogene Beu, A.G., Maxwell, P.A., 1990. Cenozoic Mollusca of New biogeographic provinces must be based on a more Zealand. New Zealand Geological Survey Paleontological quantitative approach, utilizing zoogeographic coef®- Bulletin 58, 1±518. cients for more than one group of benthic molluscs. Bukry, D., 1973. Low-latitude coccolith biostratigraphic zonation. 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