Sedimentary facies and reconstruction of a transgressive coastal plain with coal formation, Paleocene, Spitsbergen, Arctic Norway

Abstract

Analysis of coal-bearing strata in the Paleocene Firkanten Formation in the Central Tertiary Basin of Spitsbergen (Svalbard) has shown that deposition was in a coastal plain setting. Interpretation of numerous cores indicates that deposition occurred in coastal plain mires, lagoons, tidal inlets, barrier bars and shoreface environments. These form a series of shallowing-up successions metres to tens of metres thick.Correlation between boreholes over distances in excess of 100 km proved challenging with no regional marker horizons. However, by constructing paleogeographic maps as part of the process of correlating, and by using analogous modern coastal areas as indicators of facies belt widths, a correlation scheme that provides patterns of facies distribution that are consistent in three dimensions has been created. The resulting stratigraphic framework comprises parasequences grouped into parasequence sets that show an overall retrogradational pattern representing a stepwise transgression over a basin floor that was subsiding due to flexural subsidence. Absence of incision or other evidence for relative sea-level fall within the whole succession suggests that flexural subsidence was sufficient to keep pace with eustatic sea-level falls. The basal unconformity surface is overlain by a poorly sorted deposit of reworked regolith that forms a strongly diachronous unit, occurring at the base of successive parasequences. Individual parasequences formed in response to relative sea-level rises that are considered likely to be eustatic in origin and resulted in flooding of the coastal plain. Centimetre-scale analysis of the coal maceral distribution through the thickness of the lowermost major coal seam indicates that there were also higher-frequency fluctuations of relative sea level, possibly at Milankovitch-scale, during the deposition of individual parasequences. This new facies model and interpretation of the subsidence history of the basin provides a framework for understanding the distribution of sediments within a coal-bearing coastal plain succession.

Svalbard Composite Tectono-Sedimentary Element, Barents Sea

“…Oligocene indicates a shift from transpression to transtension driven by changes in plate motion (Maher et al, 1997;Braathen et al, 1999;Maher et al, 2020).…”

“…the Firkanten, Grumantbyen and Hollendardalen formations). The paralic lower part of the Firkanten Formation represent the most important coal-bearing unit in Svalbard (Nøttvedt, 1985;Lüthje et al, 2020).…”

The Importance of Eurekan Mountains on Cenozoic Sediment Routing on the Western Barents Shelf

“…Subsidence and basin development started during the Paleocene in relation to the evolving west Spitsbergen fold-and-thrust Belt, when the Firkanten Formation was deposited unconformably on Albian strata. Initial sedimentation occurred within coastal plain and shallow marine environments and is associated with coal deposits in central Spitsbergen [12]. The Paleocene Firkanten and subsequent marine mudstone-dominated Basilika and shelfal sandstonedominated Grumantbyen formations had sources located north and east of the Central Tertiary Basin based on field and petrographic observations [11].…”

“…During the Eocene, the Central Tertiary Basin was predominantly filled by material eroded from the emerging West Spitsbergen fold-and-thrust belt highlands [11] and so was an important sediment sink. This flexural basin was strongly asymmetric, meaning that subsidence was lower along its eastern margin where deposition was initially dominated by coastal plain environments [12] and clastic input from a forebulge located to the east of the basin [10,13], in addition to material sourced from the West Spitsbergen fold-and-thrust belt and transported via longshore drift [12]. At its western margin, rapid subsidence over-deepened the basin and sediment was initially supplied via submarine fans [14].…”

Growth and Distribution of Coal-Measure Source Rocks in Mixed Platform: A Case Study of Carboniferous in Bamai Area, Southwest Tarim Basin, China

“…Coal seams are commonly found in clastic strata and deposited in swampy environments in humid climates [46]. The Carboniferous in the Tarim Basin contains interbedded arid and semi-arid carbonate rocks and mudstones, with local gypsum salts, and no coal developed in other parts of the basin or the surrounding outcrops.…”