ABSTRACT During the Paleocene–Eocene, the Earth experienced the warmest conditions of the Cenozoic and reduced equator-to-pole temperature gradients. Compared to low- and mid-latitude sites, Paleogene environmental changes are less documented in Arctic regions, although such high latitude areas constitute a critical domain to constrain global climate changes. Floral and faunal assemblages indicative of exceptionally warm and humid conditions during the late Paleocene–early Eocene have been reported in several localities around the Arctic Ocean. Additional studies are required to ascertain the effects of Paleocene–Eocene global environmental changes on western Arctic regions. Here we present multiproxy data from early Eocene deltaic plain sediments of the Mackenzie Delta (Canada). This environment is characterized by littoral forest, including swamp, showing that the mangrove Avicennia grew in Arctic Canada near 75°N under air temperatures averaging 21–22 °C annually and 10–14 °C in winter and with precipitation of 1200–1400 mm/yr. Kaolinite contents are high (up to 75% of clay assemblages), as under a modern subtropical climate. The Avicennia pollens recently found in the New Siberian Islands and in Arctic Canada imply that warm and wet conditions were widespread along the Arctic coast during the early Eocene. It also suggests a marine connection between the Arctic Basin and the mid-latitude oceans. We propose that an oceanic current must have connected the Arctic Basin to the Atlantic and/or Pacific and that an internal current developed in the Arctic Basin since the early Eocene.

Abstract An integrated thermal history study of the Beaufort-Mackenzie basin of northern Canada is underway using multiparameter data gathered as part of a twelve year petroleum systems research project. New and legacy percent vitrinite reflectance (%Ro) data for approximately 81 wells have been compiled and standardized in order to make maps and cross sections showing thermal maturity trends and to provide paleotemperature constraints for thermal models. Data were quality-assessed by comparing measured %Ro values with other temperature-sensitive indicators (Rock-Eval pyrograms, liptinite fluorescence, and degree of apatite fission track (AFT) thermal annealing) and inconsistent legacy %Ro data were reinterpreted in conjunction with new sample analyses. Extensive organic matter recycling is the major issue affecting data quality and interpretation whereas other factors such as sample caving and oil staining (%Ro suppression) are important but less significant. Multikinetic AFT thermochronology data were obtained for 60 (mainly core) samples from 25 key wells with standardized %Ro data to provide constraints on the timing and rates of burial and exhumation across the study area. Also, thermal maturity and shale compaction trends were used to estimate net erosion magnitudes related to multiple phases of Tertiary deformation and exhumation. Measured %Ro is highest in exhumed strata along the southern basin margin and lowest in thick Cenozoic strata offshore (north) on the Beaufort shelf. Thermally immature strata persist to depths of > 4 km and to temperatures > 100°C on the outer Beaufort shelf due to rapid deposition of the thick (> 2.5 km) Plio-Pleistocene Iperk Sequence. Shale compaction trends suggest that 0.5-2 km of postrift Tertiary strata have been eroded from southern and southeastern onshore areas. %Ro-based erosion estimates are more variable and can give much higher values (by a factor of 3 or 4) than the compaction-based estimates, particularly in the Tertiary fold belt of the western and southern areas of the basin. There is a discontinuous increase in maturity across the unconformity that separates Jurassic synrift and Permian prerift strata along the southern basin margin. In the area south of Richards Island, maturity trends suggest that up to 4 km of Permo-Triassic strata may have been eroded prior to the deposition of Jurassic sediments. In the Anderson Plain to the east, erosion has been more extensive and Devonian rocks lie near the surface. Thermal modeling of AFT data from a Devonian sample in the Kugaluk N-02 well (AFT age: 216 Ma) suggests that exhumation was well underway in the Triassic, possibly in association with the onset of rifting. Exhumation may have continued until the Early Cretaceous, followed by reburial under 1-2 km of Cretaceous-Cenozoic sediments that were removed subsequently by erosion. The %Ro data provide important maximum paleotemperature constraints for integrated thermal history models based on multikinetic, AFT thermochronological data collected for the synrift and postrift successions.