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ANATOMY, EVOLUTION, AND PALEOENVIRONMENTAL
INTERPRETATION OF AN ANCIENT ARCTIC COASTAL PLAIN:
INTEGRATED PALEOPEDOLOGY AND PALYNOLOGY FROM THE UPPER
CRETACEOUS (MAASTRICHTIAN) PRINCE CREEK FORMATION, NORTH
SLOPE, ALASKA, USA
PETER P. FLAIG
The University of Texas at Austin, Bureau of Economic Geology, Jackson School of
Geosciences, 10100 Burnett Road, Austin, Texas 78758, USA
e-mail: peter.flaig@beg.utexas.edu
PAUL J. MCCARTHY
Department of Geology and Geophysics, and Geophysical Institute, University of Alaska, P.O.
Box 755780, Fairbanks, Alaska 99775, USA
AND
ANTHONY R. FIORILLO
Perot Museum of Nature and Science, 2201 N. Field St., Dallas, Texas 75201, USA
ABSTRACT: The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.)
exposed along the Colville River in northern Alaska records high-latitude, alluvial sedimentation and soil
formation on a low-gradient, muddy coastal plain during a greenhouse phase in Earth history. We
combine sedimentology, paleopedology, palynology, and paleontology in order to reconstruct detailed
local paleoenvironments of an ancient Arctic coastal plain. The Prince Creek Fm. contains quartz- and
chert-rich sandstone and mudstone-filled trunk and distributary channels and floodplains composed of
organic-rich siltstone and mudstone, carbonaceous shale, coal, and ash-fall deposits. Compound and
cumulative, weakly developed soils formed on levees, point bars, crevasse splays, and along the margins
of floodplain lakes, ponds, and swamps. Abundant organic matter, carbonaceous root traces, Fe-oxide
depletion coatings, and zoned peds (soil aggregates with an outermost Fe-depleted zone, darker-colored
Fe-rich matrix, and lighter-colored Fe-poor center) indicate periodic waterlogging, anoxia, and gleying,
consistent with a high water table. In contrast, Fe-oxide mottles, ferruginous and manganiferous
segregations, bioturbation, and rare illuvial clay coatings indicate recurring oxidation and periodic drying
of some soils. Trampling of sediments by dinosaurs is common. A marine influence on pedogenesis in
distal coastal plain settings is indicated by jarosite mottles and halos surrounding rhizoliths and the
presence of pyrite and secondary gypsum. Floodplains were dynamic, and soil-forming processes were
repeatedly interrupted by alluviation, resulting in weakly developed soils similar tomodern aquic
subgroups of Entisols and Inceptisols and, in more distal locations, potential acid sulfate soils. Biota,
including peridinioid dinocysts, brackish and freshwater algae, fungal hyphae, fern and moss spores,
projectates, age-diagnostic Wodehouseia edmontonicola, hinterland bisaccate pollen, and pollen from
lowland trees, shrubs, and herbs record a diverse flora and indicate an Early Maastrichtian age for all
sediments in the study area. The assemblage also demonstrates that although all sediments are Early
Maastrichtian, strata become progressively younger from south to north.
A paleoenvironmental reconstruction integrating pedogenic processes and biota indicates that polar
woodlands with an angiosperm understory and dinosaurs flourished on this ancient Arctic coastal plain
that was influenced by seasonally(?) fluctuating water table levels and floods. In contrast to modern polar
environments, there is no evidence for periglacial conditions on the Cretaceous Arctic coastal plain, and