Coop Phase I - Crustal Onshore-Offshore Project
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The five-year Crustal Onshore-Offshore Project (Coop) is an integrated data acquisition and interpretationproject established to study the onshore-offshore relationships in the northeastern North Sea and Møre-Haltenbankenarea. The Coop Phase I Report summarises the results from the Norwegian North Sea and western Norway. Newaeromagnetic, gravity and petrophysical data as well as heat flow data have been acquired. All new data werecompiled with existing data. Information on mainland basement structures, deep weathering and heat production hasbeen extrapolated to the offshore region. We conclude that the Norwegian strandflat is an exhumed weathered andpeneplaned surface of Late Triassic to Early Jurassic age that has been modified and levelled during Pleistoceneerosion. This surface was preserved beneath Late Jurassic and Cretaceous strata until the Neogene. Support for thisconclusion comes from the AMAGER mapping and the occurrence of a relatively flat and gently westward-dippingtop of basement beneath the Jurassic sedimentary rocks close to the coastline. The heat generation of the mainlandbasement rocks has been calculated from the chemical analyses of the U, Th and K contents in c. 2000 bedrocksamples and airborne radiometric measurements along the coast of western Norway. The heat generation varies withalmost one order of magnitude. Temperature logging has been carried out in Fyllingsdalen (Bergen) and Ullandhaug(Stavanger). The heat flow was calculated based on temperature logging and thermal conductivity data. The observedthermal gradients are 16.5 \u00B0C\/km in Fyllingsdalen and 13 \u00B0C\/km at Ullandhaug. Tentative palaeoclimatic correctionsfor Fyllingsdalen and Ullandhaug vary from 15 to 30 mW\/m\u00B2 (i.e., 20-40 % of the original heat-flow values). Twodifferent scenarios show corrected heat-flow values which vary from 43 to 51 mW\/m\u00B2 at Ullandhaug and from 59 to74 mW\/m\u00B2 in Fyllingsdalen. The increased heat flow in Fyllingsdalen is attributed to high values of radiogenic heatproduction within the Løvstakken granite. Crustal models of the Norwegian North Sea and western Norway have beenestablished from gravity, magnetic, seismic, well log and bedrock mapping data. By attributing thermal properties(e.g., radiogenic heat production and thermal conductivity) to the individual basement bodies we have calculated theheat flow from the basement into the sedimentary basins. The observed and modelled heat flow is strongly controlledby the lithology and structures in the crust. The temperature at a depth of 5 km in the Egersund and Stord basins is,for example, estimated to c. 155 \u00B0C and 170 \u00B0C, respectively. A map of Quaternary sand channels in the NorwegianNorth Sea has been produced. Plans for Coop Phase II are summarised at the end of the report.