Paper No. 232-14
Presentation Time: 9:00 AM-6:30 PM
REGIONAL VARIABILITY ACROSS A LATE CRETACEOUS (MAASTRICHTIAN) ARCTIC GREENHOUSE CRITICAL ZONE: A COMPARATIVE ASSESSMENT OF THE PRINCE CREEK AND LOWER CANTWELL FORMATIONS, ALASKA, USA
New numerical ages (U-Pb) from the Lower Cantwell Formation (LCF), Denali National Park, Alaska, allow direct correlation with dinosaur bonebeds of the Prince Creek Formation (PCF), North Slope, Alaska, and provide an opportunity to examine regional variability across ~ 10o of latitude within a Late Cretaceous (Maastrichtian) arctic greenhouse critical zone. The LCF consists primarily of axial braided rivers, alluvial fans, floodplains, ponds and small lakes. Paleosols exist but they are uniformly poorly developed. Abundant plant megafossils are present but fossil pollen recovery is poor. A rich invertebrate and vertebrate ichnofauna is known from the LCF and, at least with respect to the hadrosaur and ceratopsian record, adult and juvenile forms are known. The LCF, located at a paleolatitude of 65-75o N had a MAT of ~ 7-8 oC and a MAP of ~ 350-1550 mm y-1that decreased by an order of magnitude during a period of elevated temperature in the Middle Maastrichtian. The PCF consists primarily of small distributary channels, crevasse splays, small ponds and abundant paleosols. Large trunk channels fed this delta plain distributary network. Paleosols are weakly to moderately well-developed with evidence of redoxymorphic processes, weak clay illuviation and, in some cases, andic soil properties resulting from volcanic ash-charged parent materials. The paleosols suggest generally poorly drained conditions punctuated by periods of drying that were probably related to the seasonal light regime. Plant macrofossils are not abundant but paleosols contain a diverse palynoflora. In contrast to the LCF, the rich fossil vertebrate record is known largely from dinosaur skeletal remains. The PCF located at 75-85o N paleolatitude, had a MAT of ~ 5-7 oC and MAP of ~ 500-1500 mm yr-1. These formations document a Late Cretaceous cool temperate arctic critical zone with diverse flora, fauna, paleolandscapes, and paleoclimate adjusted to local tectonics and proximity to the coast along a North-South transect.