Brachiopods from Late Jurassic-Early Cretaceous hydrocarbon seep deposits, central Spitsbergen, Svalbard

Late Jurassic–Early Cretaceous (Late Volgian–latest Ryazanian) rhynchonellate brachiopods are described from eight out of 15 hydrocarbon seep deposits in the Slottsmøya Member of the Agardhfjellet Formation in the Janusfjellet to Knorringfjellet area, central Spitsbergen, Svalbard. The fauna comprises rhynchonellides, terebratulides (terebratuloids and loboidothyridoids) and a terebratellidine. The rhynchonellides include: Pseudomonticlarella varia Smirnova; Ptilorhynchia mclachlani sp. nov.; and Ptilorhynchia obscuricostata Dagys. The terebratulides belong to the terebratuloids: Cyrtothyris? sp.; Cyrtothyris aff. cyrta (Walker); Praelongithyris? aff. borealis Owen; and the loboidothyridoids: Rouillieria cf. michalkowii (Fahrenkohl); Rouillieria aff. ovoides (Sowerby); Rouillieria aff. rasile Smirnova; Uralella? cf. janimaniensis Makridin; Uralella? sp.; Pinaxiothyris campestris? Dagys; Placothyris kegeli? Harper et al.; and Seductorithyris septemtrionalis gen. et sp. nov. The terebratellidine Zittelina? sp. is also present. Age determinations for all but one of the brachiopod-bearing seeps are based on associated ammonites. Five of the seep carbonates have yielded Lingularia similis?, and it is the only brachiopod species recorded from two of the seeps. Other benthic invertebrate taxa occurring in the seeps include bivalves, gastropods, echinoderms, sponges, and serpulid and non-serpulid worm tubes. The brachiopod fauna has a strong Boreal palaeobiogeographic signature. Collectively, the Spitsbergen seep rhynchonellate brachiopods exhibit high species richness and low abundance (<100 specimens from 8 seeps). This contrasts markedly with other Palaeozoic–Mesozoic brachiopod-dominated seep limestones where brachiopods are of low diversity (typically monospecific) with a super-abundance of individuals. The shallow water environmental setting for the Spitsbergen seeps supported a diverse shelf fauna, compared to enigmatic Palaeozoic–Mesozoic brachiopod-dominated seeps

Bivalves from the latest Jurassic-earliest Cretaceous hydrocarbon seep carbonates from central Spitsbergen, Svalbard

The bivalve fauna from the latest Jurassic–earliest Cretaceous hydrocarbon seep deposits from central Spitsbergen, Svalbard comprises at least 17 species, four of which belong to chemosymbiotic taxa often found at seeps. These are the solemyid Solemya (Petrasma) cf. woodwardiana; Nucinella svalbardensis sp. nov., which belongs to a group of large Nucinella species known from seeps and deep water environments; the lucinid bivalve, Tehamatea rasmusseni sp. nov.,included in a genus widely distributed in other Jurassic–Cretaceous seeps; and Cretaxinus hurumi gen. et sp. nov., which is the oldest known thyasirid and is discussed in relation to other large seep-restricted genera in this family. The remaining species in the fauna belong to ‘background’ genera known from coeval normal marine sediments, mostly from the Boreal area. These include the nuculid Dacromya chetaensis, two new malletiids (Mesosaccella rogovi sp. nov. and M. toddi sp. nov.), the oxytomiid Oxytoma octavia, at least three Buchia species, at least two pectinids, including Camptonectes (Costicamptonectes) aff. milnelandensis and Camptonectes (Camptochlamys) clatrathus, the limid Pseudolimea arctica, the arcticid Pseudotrapezium aff. groenlandicum, and the pholadomyid Goniomya literata. The large number of ‘background’ species in the bivalve fauna is probably a reflection of the shallow-water setting of the Svalbard seeps. This might also explain the lack of the seep-restricted modiomorphid bivalve Caspiconcha from the fauna. With solemyids, Nucinella, lucinids and thyasirids, the latest Jurassic–earliest Cretaceous bivalve seep fauna of Svalbard contains typical representatives of the Mesozoic bivalve seep faunas, both long established and young evolutionary colonists

Gastropods from the Late Jurassic–Early Cretaceous seep deposits in Spitsbergen, Svalbard

Eleven gastropod species from seven latest Jurassic–earliest Cretaceous hydrocarbon seep deposits from central Spitsbergen, Svalbard are described and illustrated. Six new species and one new genus are introduced. Sassenfjordia gen. nov. is tentatively classified as a naticoid and is characterized by a naticiform gross teleoconch morphology and a large protoconch ornamented with spiral ribs, similar to those present in the subfamily Sininae. The patellogastropod ?Pectinodonta borealis sp. nov. represents the oldest occurrence of pectinodontid limpets in chemosynthesis-based associations. The colloniid Hikidea svalbardensis sp. nov. is the oldest confirmed occurrence of this genus so far. The eucyclid Eucycloidea bitneri sp. nov. is the second report of an occurrence of this genus at hydrocarbon seeps (both of which come from the Paleo-Barents Sea). Abyssomelania sp. is the third known, and the oldest occurrence of this genus. Hudlestoniella hammeri sp. nov. represents another occurrence of this genus at seeps in the Paleo-Barents Sea; its current higher-rank assignment is reviewed herein. It may belong either to the rissoids, as previously suggested, or to the abyssochrysoids (or zygopleurids). A fossil identified as Cretadmete sp. is here classified in the Purpurinidae, a family of stem neogastropods or tonnoideans. The heterobranch Hyalogyrina knorringfjelletensis sp. nov. is the oldest occurrence of hyalogyrinids in chemosynthesis-based associations. Several oldest occurrences of seep taxa in moderately shallow seeps in Spitsbergen suggest that the previously questioned onshore-offshore hypothesis of seep and vent colonization should be carefully re-investigated

A Boreal serpulid fauna from Volgian-Ryazanian (latest Jurassic-earliest Cretaceous) shelf sediments and hydrocarbon seeps from Svalbard

Serpulid polychaete tubes are described from Volgian-Ryazanian sediments (?Pyrgopolon decorata (Stolley, 1912), ?Pyrgopolon aff. nodulosum (Lundgren, 1883)) and four contemporaneous hydrocarbon seep deposits (?Pyrgopolon aff. nodulosum, ?Pyrgopolon sp. A, Propomatoceros sp. A, Nogrobs aff. quadricarinata Münster in Goldfuss, 1831) from Spitsbergen, Svalbard. These are the oldest serpulid tubes yet described from fossil hydrocarbon seep deposits, and comprise the most diverse fossil seep serpulid fauna known to date. The genera Propomatoceros Ware, 1975 and Nogrobs de Montfort, 1808 have their first fossil occurrence elsewhere in the Early Jurassic and then appear in the Svalbard seeps much later. This is the first report of ?Pyrgopolon de Montfort, 1808 from a fossil seep site

Palynology of Early Cretaceous (Barremian to Aptian) hydrocarbon (methane) seep carbonates and associated mudstones, Wollaston Forland, Northeast Greenland

Palynostratigraphic and palynofacies analysis have been performed on hydrocarbon seep carbonate, carbonate nodule and mudstone samples from the Early Cretaceous Kuhnpasset Beds in the Kuhnpasset area of Wollaston Forland, Northeast Greenland. Three informal palynostratigraphic zones have been defined based on dinoflagellate cyst occurrences. The zones range from ?early Barremian to early Aptian in age, and correlate with previously defined dinoflagellate cyst zones in Northeast Greenland. These zones indicate hydrocarbon seepage in Kuhnpasset spanned the ?early–late Barremian age range, but did not continue into the Aptian, and thus seep activity continued for as much as three million years. Palynofacies analysis is used to interpret the depositional environment of the Kuhnpasset Beds and indicate that the hydrocarbon seeps and associated mudstones from this sedimentary sequence were deposited in a proximal shelf setting

The palaeoecology of latest Jurassic-earliest Cretaceous hydrocarbon seep carbonates from Spitsbergen, Svalbard

Latest Jurassic–earliest Cretaceous hydrocarbon seeps from Spitsbergen, Svalbard, are known to contain unusual fauna, lacking most of the species characteristic for roughly coeval seep deposits. This study summarizes and analyses the fauna from 16 seep carbonate bodies from Spitsbergen to explain its composition. The seeps formed in a shallow epicontinental sea with widespread deposition of fine-grained, organic-rich sediments. They are spread over a relatively large area and are positioned roughly in the same interval, indicating seepage over extensive areas of the palaeo-Barents Sea. The seep fauna is very species rich and with low dominance, comprising 54 species, with a composition similar to that of Jurassic–Cretaceous normal-marine environments of other Boreal seas. Seep-restricted fauna is not abundant and is represented by four species only. Hokkaidoconchids and possible siboglinid worm tubes characteristic for high sulphide fluxes are rare. Apart from seep-restricted sulphide-mining lucinid and thyasirid bivalves, chemosymbiosis was also a source of nourishment for background solemyid and nucinellid bivalves, all of which take sulphide from infaunal sources. This all suggests a relatively weak sulphide flux. The high diversity and low dominance of the fauna and significant richness and abundance of background species is typical for shallow water seeps

The type section of the Vikinghogda Formation:a new Lower Triassic unit in central and eastern Svalbard

The Vikinghøgda Formation (250 m) is defined with a stratotype in Deltadalen-Vikinghøgda in central Spitsbergen. The Vikinghøgda Formation replaces the Vardebukta and Sticky Keep Formations of Buchan et al. (1965) and the lower part of the Barentsøya Formation of Lock et al. (1978) as extended geographically by Mørk, Knarud et al. (1982) in central Spitsbergen, Barentsøya and Edgeøya. The formation consists of three member: the Deltadalen Member (composed of mudstones with sandstones and siltstones), the Lusitaniadalen Member (dominated by mudstones with thin siltstone beds and some limestone concretions) and the Vendomdalen Member (composed of dark shales with dolomite interbeds and nodules). The Lusitaniadalen and Vendomdalen members replace the former Sticky Keep Formation/ Member in the siirne areu. The Vikinghøda Formation can be followed through central and eastern Spitsbergen to Barentøya and Edgeøya and includes all sediments between the chert-rich Kapp Starostin Formation (Permian) and the organic-rich shales of the Botneheia Formation (Middle Triassic). The subdivision into three members is also reflected in the organic carbon content and palynofacies. Upwards, each succeeding member becomes more distal, organic-rich and oil-prone than the one below. The Vikinghøda Formation is well-dated by six ammonoid zones, although the transitional beds between the Deltadalen and Lusitaniadalen members lack age diagnostic macrofossils. Corresponding palynozonation and magnetustratigraphy have also been determined. The overall stratigraphical development correlates well with other key Triassic areas in the Arctic, although intervals in the late Dienerian and early Smithian may be condensed or missing