| Summary: | Upper Permian deposits from the eastern margin of the Helgeland Basin, offshore Norway, are known to contain two organic-carbon-rich (OCR) intervals within the Lower Turbidite Unit. These intervals were so far not proven in the deeper basinal areas and their depositional conditions in the margin areas were not fully understood. In order to understand the general depositional conditions and lateral extents of the two organic rich intervals, Upper Devonian-Triassic successions have been investigated. Core logging, analysis of element proxies, qualitative and quantitative seismic interpretation and intercept and gradient (IG) crossplotting were used to investigate these successions in the Trøndelag Platform, specifically the Helgeland and Froan basins and partly the Nordland Ridge. Seismic interpretation, both qualitative and quantitative, and IG crossplotting were used to investigate possible geophysical manifestations of these upper Permian OCR sediments in the deeper basinal areas. Qualitative seismic interpretation, which focused on the analysis of the Upper Devonian-Triassic sedimentary fill geometries and fault-strata relationships, and a combination of core logging and element proxies were used to assess conditions that controlled deposition and preservation of the OCR sediments. These conditions include local tectonic developments, which are not as well understood as the regional development, and variation in oxygen levels in the deep basinal areas. A portable X-Ray Fluorescence (PXRF) scanner was used to determine major, minor, and trace element concentrations. The measurements of these element concentrations on core started below the lower organiccarbon-rich interval and continued above the upper organic-carbon-rich interval to track changes over time that might indicate what caused deposition to change. Changes in element values were then correlated to grain size, deposit types and organic content to understand the sedimentological influence on element distributions. Results show that the Trøndelag ...
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