Coal rank data and tectonic structure of Mesozoic and Paleogene sediments in North Greenland
Hans-Jürgen Paech, Solveig Estrada, "Coal rank data and tectonic structure of Mesozoic and Paleogene sediments in North Greenland", Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens, Karsten Piepjohn, Justin V. Strauss, Lutz Reinhardt, William C. McClelland
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Vitrinite reflectance (Rr) data, combined with structural field evidence, allow insights into the thermal and tectonic history of North Greenland. During the tectonism at the Cretaceous–Paleocene boundary, the thermal imprint varies considerably, mostly controlled by active fault zones. The Upper Cretaceous sequences along the Harder Fjord Fault Zone show Rr values between ~3.2% (Frigg Fjord area) and ~2.1% (Depotbugt area). Along the Trolle Land Fault Zone, Rr varies between 1.3% and 2.9% in the Herlufsholm Strand area, and between 1.6% and 2.2% in the Kilen area. These maturity variations along regional fault zones are connected with varying deformation intensity and explained by unequal conductive heat flow. In the Kap Washington Group, the high coal rank attaining 5.4% Rr is associated with ductile deformation, and is additionally influenced by magmatic activity, i.e., convective heat flow. The coalification is low in regions a greater distance away from active faults, e.g., in Lower Cretaceous sediments of Herluf Trolle Land with ~0.5% Rr. The Paleogene Thyra Ø Formation was deposited following deformation and thermal imprint at the Cretaceous–Paleogene boundary. It remained undeformed and shows a reduced Rr of ~0.55%, reflecting burial thermal imprint. A later thermal event (known from the literature) that affected Mesozoic sediments, and possibly also locally Paleogene sediments close to the continental margin, is assumed to be related to heat flow from the active plate boundary between northeast Greenland and Svalbard.
Based on detailed geochemical and mineralogical studies, thin, yellowish jarosite-bearing, clayey horizons within the Thyra Ø Formation are interpreted to probably originate from volcanic ashes erupted during the first stage of the opening of the North Atlantic.