Evolution of an Arctic open-shelf carbonate platform, Spitsbergen bank (Barents sea)

Spitsbergen Bank is the largest open-shelf cold-water carbonate platform in the Arctic region. Carbonate production is centered around two main carbonate ''factories.'' The first one, kelp forests growing on the shallowest parts of the platform are the main source area for barnacle sands (i.e., Balanus crenatus). These mobile carbonate sands are transported within a huge clockwise gyre of polar water over the platform. This gives rise to a thin veneer of skeletal sand on the platform interior and carbonate mega-dunes at the margin. At these high latitudes, extreme seasonality is reflected in variation in sea ice cover over the bank and changes in sediment dynamics. Migration of marginal mega-dunes is related to heavy storm events in late autumn/early winter. Smoothing of the dune relief occurs by bottom traction currents through the rest of the year. The second carbonate ''factory'' is situated on the flanks of the platform, where high productivity conditions are established along the Polar Front at the zone between Atlantic and Arctic water masses. Very efficient bentho-pelagic coupling (e.g., a rapid transfer of planktic food to the benthic communities), accounts for the development of a high biomass. The biota features dense colonies of infaunal bivalves as well as Balanus balanus-hydrozoan-soft coral-sponge-bryozoan buildups. The postglacial succession of cold-water settings on Spitsbergen Bank display a distinct evolutionary trend which highlights variable balances between the main driving forces on cyclically-glaciated carbonate platforms. There is a complete switch-over between the two end-member conditions: maximum drowning and eustatic sea-level lowstands during glacial periods Versus maximum efficiency of glacio-isostatic uplift and eustatic sealevel highstand in the Holocene time. These changes in platform configuration are associated with a shift in sedimentary regimes from low-energy, proximal-glaciomarine settings during the glacial and early postglacial period to high-energy, distal-glaciomarine conditions in Holocene time. Evolutionary phases of this shift can be deduced from detailed analysis of facies belts on Spitsbergen Bank and are summarized in a hypothetical model for two successive glacial/interglacial cycles. This model may serve as a reference for the interpretation of fossil counterparts.