Lower–Middle Jurassic foraminiferal and ostracode biostratigraphy of the Barents Sea shelf

Abstract

The Barents Sea shelf is an attractive target as a prospective large petroleum province. Further development of geological and geophysical exploration in the area requires high-resolution biostratigraphic constraints and update stratigraphic charts. The zonal succession of Lower and Middle Jurassic assemblages of foraminifers and ostracodes of the Barents Sea fits well the division for northern Siberia based on correlated independent Jurassic and Cretaceous zonal scales on all main microfossil groups, of which some scales were suggested as the Boreal Zonal Standard. The stratigraphic range of the Barents Sea microfossil assemblages has been updated through correlation with their counterparts from northern Siberia constrained by ammonite and bivalve data. Joint analysis of foraminiferal and ostracode biostratigraphy and lithostratigraphy of the sections allowed a revision to the stratigraphic position and extent of lithological and seismic units. The discovered similarity in the Lower and Middle Jurassic lithostratigraphy in the sections of the Barents Sea shelf and northern Siberia, along with their almost identical microfossil taxonomy, prompts similarity in the Early and Middle Jurassic deposition and geological histories of the two areas.

Impact of the Middle Jurassic diversification of Watznaueria (coccolith-bearing algae) on the carbon cycle and δ13C of bulk marine carbonates

“…The first hypothesis takes into account a Middle Jurassic production of nannofossils restricted to the shallow seas of the continental shelf (Hay, 2004), which were located in between 60°N and 60°S. We selected this latitude range because sections from Siberia and Alaska located north of 60°N, and Canada and Scotland located slightly below 60°N during the Middle Jurassic do not contain limestone or marlstone deposits (Imlay, 1976;Morton, 1992;Hall et al, 2004;Basov et al, 2009). Following this hypothesis, S would correspond to~6% of the Earth's surface during this period (measured from Blakey, 2005).…”

Jurassic and Cretaceous stratigraphy of the Anabar area (Arctic Siberia, Laptev Sea coast) and the Boreal zonal standard

“…A succession of four biostratigraphic units (Fig. 10) also defined in all other Arctic regions (Azbel' et al, 1991;Basov et al, 1989Basov et al, , 2008 was identified in Albian sediments of northern and northwestern areas of West Siberia (Nesterov, 1991).…”

“…Some biostratigraphic units (KF1, KF2, KF4, KF5) are defined in all Arctic regions: West Siberia, East Siberia, Arctic Alaska, Arctic Canada, and Barents Sea shelf (Basov et al, 2008;Fowler and Braun, 1993;Shurygin et al, 2000;Wall, 1983). Since the second half of the Hauterivian, a predominantly continental regime had set in East Siberia (Fig.…”

“…12) and further modified with regard to the data on West Siberia . Some units of this scale are well defined on the Barents Sea shelf (Basov et al, 2008;Kupriyanova, 2000;Lev and Kravets, 1982;Nikolaeva and Neustrueva, 1999).…”

Late Jurassic – earliest Cretaceous prolonged shelf dysoxic–anoxic event and its possible causes

“…The range of the black shale facies here can be roughly estimated as Kimmeridgian-Ryazanian. TOC values of these black shales lie mainly between 2 and 23%, but fluctuations of TOC distribution through the succession remains unclear (Basov et al 2009). Fossils recovered from these black shales mainly belong to ammonites and Buchia; in addition to these groups, lingulid brachiopods, coleoid hooks and onychites (including big-sized megaonychites) were reported from the Volgian interval of black shales.…”