Origin of Clay Minerals In Alluvial Paleosols, Prince Creek Formation, North Slope, Alaska, U.S.A: Influence of Volcanic Ash On Pedogenesis In the Late Cretaceous Arctic

Abstract

Abstract Paleosols formed from weathering of alluvial mudstones in the Late Cretaceous (Maastrichtian) Prince Creek Formation, North Slope Alaska, are dominated by detrital smectite, discrete illite, kaolinite, chlorite, quartz, and pedogenic illite–smectite (I/S) mixed-layer clays. In the fine clay fraction ( 80%), low bulk density, phosphorus accumulation, Fe and Al mass-balance trends, and the presence of Fe–Al–humus complexes in one paleosol profile is interpreted as evidence of andic soil properties, and these paleosols are interpreted, therefore, as Andept-like alluvial soils. These results demonstrate that clay mineralogical studies, in conjunction with geochemical data of paleosols, can be used to identify paleo-andic soil properties which have not been widely recognized in the ancient rock record. Alternating wetting and drying conditions, required to form pedogenic I/S in these alluvial paleosols, resulted from a highly seasonal moisture regime in the Late Cretaceous Arctic.