Depositional environment of coal and amber during the PETM and ETM-2 hyperthermal events in northern highlatitudes (Canadian Arctic)

<p>High-latitude terrestrial records of Paleogene hyperthermal events can help to calibrate global climate models seeking a refined understanding of extreme warming events; however, such high-latitude records are rare. The Margaret Formation at Stenkul Fiord, southern Ellesmere Island, preserves a record of the early Eocene hyperthermal events. This late Paleocene to early Eocene sedimentary archive is composed of fluvially derived clastic sediments and amber-bearing coals. However, as the Eurekan deformation event caused major synsedimentary tectonic movement, resulting in substantial unconformities, the development of a reliable stratigraphic framework for Stenkul Fiord has proved challenging thus far. Field mapping and satellite image interpretation were used to identify unconformities and other tectonic structures in a section at Stenkul Fiord. In combination with a previously dated ash layer (U-Pb zircon age of 53.7 Ma, ID-TIMS) and biostratigraphic association (Graybullian, NALMA) of rare vertebrate fossils, both the PETM and ETM-2 hyperthermal events were identified. In addition, samples for new carbon isotope data of bulk coal, organic-rich sediments and ubiquitous occurring amber were collected. Using this refined stratigraphic framework the average sedimentation rates were calculated, and stratigraphic completeness of the section was evaluated. It was determined that the amount of clastic sediment deposited at Stenkul Fiord increased near the end stages of the PETM and ETM-2 hyperthermal events. This is interpreted as a response of the fluvial depositional system to an intensified hydrological cycle during the hyperthermals. This probably resulted also in discharge events, in which amber was enriched in layers due its lower density and thus their preferential mobilization and re-deposition during water flooding the swamp forest environment. Whereas amber in general shows less depleted isotope values compared to coals, this process may explain the larger offsets between the istopic composition of coals and ambers observed in some layers, respectively. This late Paleocene to early Eocene deposits at Stenkul Fiord offer further possibilities to study the effects of global warming events on terrestrial northern highlatitude depositional systems.</p>