IDENTIFICATION OF THE EOCENE THERMAL MAXIMUM 2 (ETM-2) IN A TERRESTRIAL SECTION OF THE HIGH ARCTIC BASED ON NEW U-PB ZIRCON AGES AND CARBON ISOTOPE RECORDS (STENKUL FIORD, ELLESMERE ISLAND, CANADA)

The Stenkul Fiord section on southern Ellesmere Island reveals largely fluvial clastic sediments with intercalated coal seams of the Margaret Formation of Late Paleocene/Early Eocene age according to palynology and vertebrate remains.

Field studies in recent years and interpretative mapping of a high-resolution satellite image of the area southeast of Stenkul Fiord have shown that the clastic deposits consist of at least four sedimentary units (Units 1 to 4) separated by unconformities. Several centimeter-thin volcanic ash layers, identified within coal layers and preserved as crandallite group minerals (Ca-bearing goyazite), suggest an intense volcanic ash fall activity.

Based on new U-Pb zircon ages (ID-TIMS) of three ash layers, the volcanic ash fall took place at 53.7 Ma in the Early Eocene, i.e. in range of the Eocene Thermal Maximum 2 (ETM-2) hyperthermal. Discrete negative excursions of carbon isotope records of both bulk coal and amber droplets collected from individual coal seams of the section indicate the extent of the ETM-2 hyperthermal. The coal seams with the new U-Pb zircon ages from the volcanic ash layers are situated towards the top of the negative carbon isotope curve excursions. Work is underway on new additional samples from every coal seam to overcome limitations of the previous sampling resolution and to settle that the volcanic ash layers are unquestionably within the range of the negative isotope excursion.

The identification of the ETM-2 hyperthermal provides a stratigraphic tie-point in the terrestrial Margaret Formation sediments. It permits the assignment of the lowermost sedimentary Unit 1 to the Late Paleocene-earliest Eocene and Unit 2 to the Early Eocene, whereas Unit 3 and 4 might be Early to Middle Eocene in age. Thus, the timing of syn-sedimentary movements of the Eurekan deformation, causal for the observed unconformities in the section, can be studied in detail complemented by the identification of the positions of other hyperthermals like the preceding PETM or the subsequent ETM-3 in the section.

The integration of structural studies, U-Pb zircon ages, and different carbon isotope records provides a new stratigraphic framework for further examination of the unique Early Eocene flora and fauna preserved in this high-latitude outcrop.