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

Abstract

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. □ Boreal, chemosymbiosis, Cretaceous, flux strength, Jurassic, palaeoecology.

Paleocene methane seep and wood-fall marine environments from Spitsbergen, Svalbard

“…80 km east from Sassenfjorden area in Agardhbukta on Spitsbergen, where a single carbonate body of seep origin has been discovered (Vinn et al, 2014). Spitsbergen seepage at that time was probably not very intense, since all resulting seep carbonate bodies are of small size (Hryniewicz et al, 2015). The second episode of seepage is recorded by this study.…”

“…Dypvik et al, 1991). It is likely that Jurassic-Cretaceous gas release on Spitsbergen was manifestation of accumulation of shallow gas within the organic-rich Agardhfjellet Formation hosting the Sassenfjorden seeps (Hryniewicz et al, 2015). More labile tectonic setting has been proposed for the Palaeogene 24 of Spitsbergen.…”

“…Nonetheless, the macrofaunal species diversity is still lower than in some well studied Mesozoic shallow water seep sites, for example in Late Cretaceous (Campanian) Tepee Buttes in Western Interior Seaway, where up to 30 species per butte have been recorded (e.g. Kauffman et al, 1996), or in some of the Jurassic-Cretaceous transition seeps from Sassenfjorden, where up to 32 species per seep have been documented (Hryniewicz et al, 2015). This could simply represent a collection bias, as Fossildalen seep has not been studied as extensively as the other two examples.…”

Late Jurassic–Early Cretaceous hydrocarbon seep boulders from Novaya Zemlya and their faunas

“…Some of these species had rather narrow palaeobiogeographical ranges. This is especially true for the arcticid bivalves, Dacromya and the gastropod Hudlestoniella (Table 2), which are shared only with the geographically and temporarily adjacent Svalbard seeps and Boreal ‗normal' marine sediments, and are unknown from Late Mesozoic deep water seeps (Hryniewicz et al, 2014 and references therein). Other ‗background' species belong to genera showing preference towards seep environments.…”

“…As these formed in shallow water (Hryniewicz et al, in press) and a paucity of seep-restricted species is a general feature of shallow-water vent and seep faunas (Dando, 2010 and references therein), a similar palaeobathymetric setting is likely to have influenced the structure of Novaya Zemlya seep boulder faunas. The Svalbard seeps contain only four seep-restricted species, out of over 50: a lucinid and thyasirid bivalves (Hryniewicz et al, 2014), hokkaidoconchid gastropods, and possible ‗vestimentiferan' worm tubes . Except for the hokkaidoconchids, these taxa are unknown from the Novaya Zemlya seep boulders, which is intriguing, considering they could have formed in relative proximity (Hryniewicz et al,in press,fig.…”