Paper No. 11
Presentation Time: 4:15 PM
LATE CRETACEOUS ARCTIC PALEOENVIRONMENTS FROM THE LOWER CANTWELL AND PRINCE CREEK FORMATIONS, ALASKA, USA
New numerical ages (U-Pb) from the Lower Cantwell Formation (LCF), Denali National Park, Alaska, provide evidence for direct correlation with dinosaur bonebeds of the Prince Creek Formation (PCF), North Slope, Alaska, and provide an opportunity to compare these Late Cretaceous (Maastrichtian) paleoenvironments. 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 65-75 oN, had a MAT of ~ 7-8 oC. The PCF consists primarily of small distributary channels, crevasses 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, at least in some cases, influence of volcanic ash, indicating generally poorly drained conditions punctuated by periods of drying that may have been related to the seasonal light regime. Plant macrofossils are not abundant, but paleosols contain an abundant palynoflora. In contrast to the LCF, the rich fossil vertebrate record is known largely from skeletal remains. The PCF, located at 75-85 oN paleolatitude, had a MAT of ~ 5-6 oC. These units document a Late Cretaceous, cool temperate Arctic with diverse flora, fauna and paleolandscapes adjusted to local conditions along a N-S transect. Relative abundances of hadrosaurs and ceratopsians are remarkably similar in both rock units suggesting differences in depositional settings were not primary controls for large-bodied herbivore ecological structure.