Progradational and backstepping shoreface deposits in the Ladinian to Early Norian Snadd Formation of the Barents Sea

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Abstract

ABSTRACT

Shoreface sandstone deposits within the Early Carnian part of the Snadd Formation of the Norwegian Barents Sea can be traced for hundreds of kilometres in the depositional strike direction and for tens of kilometres in the depositional-dip direction. This study uses three-dimensional seismic attribute mapping and two-dimensional regional seismic profiles to visualize the seismic facies of these shoreface deposits and to map their internal stratigraphic architecture at a regional scale. The shoreface deposits are generally elongate but show variable width from north-east to south-west, which corresponds to a sediment source in the northern part of the basin and a southward decrease in longshore sediment transport. The Snadd Formation presents an example of how large-scale progradational shoreface deposits develop. The linear nature of its shoreface deposits contrasts with more irregular, cuspate wave-dominated deltaic shorelines that contain river outlets, and instead implies longshore drift as the main sediment source. In map view, discrete sets of linear features bounded by truncation surfaces scale directly to beach ridge sets in modern counterparts. The shoreface deposits studied here are characteristic in terms of scale and basin-wide continuity, and offer insight into the contrast between shallow marine deposition under stable Triassic Greenhouse and fluctuating Holocene Icehouse climates. Findings presented herein are also important for hydrocarbon exploration in the Barents Sea, because they describe a hitherto poorly understood reservoir play in the Triassic interval, wherein the most prominent reservoir plays have so far been considered to be found in channelized deposits in net-progradational delta-plain strata that form the topsets to shelf-edge clinoforms. The documented presence of widespread wave-dominated shoreface deposits also has implications for how the relative importance of different sedimentary processes is considered within the basin during this period.

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