Quantitative Biofacies Analysis to Identify Relationships and Refine Controls on Paleosol Development, Prince Creek Formation, North Slope Alaska, USA

Abstract

Late Cretaceous coastal plain deposits of the Prince Creek Formation (PCF) offer a rare glimpse into an ancient, high-latitude, arctic greenhouse ecosystem for which there is no modern analog. Here, we employ quantitative biofacies analysis to explore the spatio-temporal variability in PCF palynomorph and microbiota assemblages from nine paleosol horizons exposed along the Colville River, North Slope, Alaska. Biofacies results provide insight into paleoenvironmental controls on the coastal plain ecosystem. Cluster and ordination analyses recognize five biofacies and the following two assemblage types: (1) fern and moss dominated assemblages and (2) algae dominated assemblages. Ordination arrays biofacies along environmental gradients related to soil moisture and marine influence. Fern and moss dominated biofacies from regularly water-logged paleosols along lake and swamp margins on the lower delta plain clearly segregated from algae dominated assemblages of periodically drier levee-overbank paleosols. These results support previous interpretations from the sedimentology, paleopedology, and geochemistry of PCF paleosols that suggest that fluctuations in the water table, related to seasonal river discharge and variations in topography and drainage, controlled soil development and vegetation growth across the coastal plain. This quantitative biofacies-based approach provides an independent predictive tool and cross-check for interpreting environmental conditions along any ancient coastal ecosystem.

Stable Isotope Tracers of Cretaceous Arctic Paleoprecipitation

“…These include algae and bacteria, submerged and floating organic matter, and emergent and terrestrial plants. This agrees with the depositional environment and other palaeobotanical studies of this unit [31,32] The terrestrial plants in this unit are likely predominantly conifers. This is based on the abundance of conifer-derived diterpenoid compounds and the near absence of angiosperm-derived triterpenoids.…”

“…These include algae and bacteria, submerged and floating organic matter, and emergent and terrestrial plants. This agrees with the depositional environment and other palaeobotanical studies of this unit [31,32] The terrestrial plants in this unit are [26]. These Cretaceous data ranges were compared with δD and δ 18 O data compiled from Late Paleocene to Early Eocene Arctic localities [12] represented by the orange filled box.…”

“…Cretaceous samples are primarily from paleosol horizons, thin lacustrine deposits, or coal. Cretaceous paleosols are weakly developed compound and cumulate soils that formed on the levees, point bars, and crevasse splays of channel systems, and along the margins of lakes, ponds, and swamps [31,32]. Soil development was frequently interrupted by input of sediments during river flooding events, resulting in paleosols that are similar to modern Entisols or Inceptisols [31].…”