Palaeogeographic development and economic potential of the coal-bearing palaeocene Todalen Member, Spitsbergen

Palaeocene high-latitude coals from the Todalen Mbr. Central Tertiary Basin, Svalbard present an opportunity to understand the processes which controlled Arctic peat formation. Coals from this region have produced sub-economic quantities of bitumen during the 1920’s. Previous palaeogeographic models show significant variation between studies favouring deltaic and tidal wetland conditions. In addition, coal geochemistry studies have been limited to characterisation with little integration with palaeogeographic studies. This study utilises a large database of drill-logs to create cross sections and coal isopach maps to examine the spatial relation between seam thickness and palaeotopography. Palaeotopography is defined by mapping a ‘valley indicator’; the Grønfjorden bed, a fluvial conglomerate representing the first Palaeocene sedimentation. In addition, organic petrology organic and inorganic geochemistry were applied to samples from two mine sections and two boreholes to examine how coal quality and oil potential changed both within and between seams. The cross sections and isopach maps reveal that landscape had a significant but diminishing control upon peat accumulation. Thickest peats consistently formed at the break-in slope whilst topographic lows acted as areas of preferential channel formation and conduits for clastic sedimentation. Evolution of the landscape control had a significant control upon groundwater supply. As landscape control decreased the coals moved from isolated, raised bogs (Svea Seam) to laterally expansive minerotrophic fens (Svarteper and Askeladden Seams). Evidence of increasing marine influence and higher groundwater input was also observed from the Svea Seams to the Askeladden seam. In the Svea Nord and Longyear seam, supply of lithophile elements (Al, Ti, Na, K) is shown to be controlled by dust supply controlled by orbital cyclicity. By the Svarteper/Askeladden period lithophile element concentrations are controlled by clastic supply. Ca, Mg and Fe appear to be derived from groundwater. Sulfur concentration primarily reflects the supply of marine sulfur. Upper Todalen coals (Longyear, Svarteper and Askeladden) have significantly more oil potential than the Svea Seams with estimated retorting yields of 170-190kg/ton vs. 50kg/ton respectively. The Longyear seam exhibits relatively high HI values (ca. 300-400 mg/g TOC) consistent with a mixed Type II/III kerogen source. Greatest oil potential is shown to be favoured by formation within a fen environment, with high bacterial degradation (>100μg/g TOC hopanes), marine influence (>0.5wt% sulfur, Fe/S