From detached to attached carbonate buildup complexes — 3D seismic data from the upper Palaeozoic, Finnmark Platform, southwestern Barents Sea

Abstract

Carbonate buildups were abundant during the Palaeozoic. Three-dimensional seismic data from the Finnmark Platform, Barents Sea, has been used to reconstruct the evolution of laterally extensive carbonate buildup complexes in space and time. The results suggest that the location of Upper Palaeozoic warm- and cool-water carbonate buildups from the Finnmark Platform is controlled by faults and the sea floor morphology at the time of their growth. A fluctuating sea level affected the growth of the carbonate buildups, but they also influenced their own environment by forming lagoons, atoll-like ridges and possibly areas with restricted circulation. Warm-water carbonate buildups, forming ridges and isolated mounds, occur in the Gipsdalen Group (latest Serpukhovian–mid-Sakmarian), where they initially grew in a detached platform setting. The carbonate buildups are several tens of kilometres long, up to 2.5 km wide and 300 m thick, and interpreted to consist of vertically stacked complexes of sub-seismic scale carbonate buildups. Evaporites were deposited and later subject to karstification, possibly during a period of sub-aerial exposure, before a transgression and the subsequent carbonate deposition and buildup growth bridged the detached platform with the attached platform. In the Bjarmeland Group (Lower Permian) 0.35–4.8 km wide, 1.5–27 km long and 60–420 m thick cool-water bryozoan-dominated straight, sinuous and continuous carbonate ridges or atoll-like ridges are located on top of the warm-water carbonate structures. Three-dimensional maps of Upper Palaeozoic carbonate buildups document their geomorphology, distribution and size through time. The lateral and vertical growth of carbonate buildups has been reconstructed, revealing how their distribution changed over time and with changing environmental settings.