Integrated Paleopedology and Palynology from Alluvial Paleosols of the Cretaceous (Cenomanian) Dunvegan Formation, Alberta and British Columbia, Canada: Paleoenvironmental and Stratigraphic Implications
Published:January 01, 2013
Jacob R. Mongrain, Paul J. McCarthy, A. Guy Plint, Sarah J. Fowell, 2013. "Integrated Paleopedology and Palynology from Alluvial Paleosols of the Cretaceous (Cenomanian) Dunvegan Formation, Alberta and British Columbia, Canada: Paleoenvironmental and Stratigraphic Implications", New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems, Steven G. Driese, Lee C. Nordt
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The Dunvegan Formation is a mid-Cretaceous alluvial plain-deltaic deposit exposed along the Rocky Mountain Foothills and Peace River Valley of Alberta and British Columbia, Canada. A multiproxy approach, combining paleosol micromorphology, geochemistry, and mineralogy with palynology, is used to reconstruct the climatic, pedogenic, and depositional history of this high-latitude setting during a greenhouse climate regime. Intrinsic features of paleosols within the Dunvegan Formation suggest a warm to cool temperate paleoclimate. These paleosols experienced multiple depositional phases superimposed on pedogenic phases that resulted in complicated compound, complex, and welded paleosol profiles. Well-preserved palynomorph assemblages within the paleosols are composed primarily of fern spores, with small percentages of gymnosperm pollen. The palynomorphs suggest a humid paleoclimate ranging from cool temperate to subtropical. The abundance of fern spores in all of the paleosol profiles suggests early successional colonization of the floodplain. Better-developed interfluve paleosols contain greater percentages of tree pollen, indicating the presence of nearby forests. Within interfluve paleosols, intervals barren of pollen coincide with sequence boundaries identified on the basis of micromorphology and geochemistry. Our combined paleopedological and palynological data sets, together with macrofloral and geochemical paleoclimate indicators, suggest that the Dunvegan alluvial-coastal plain complex probably formed under a humid, warm to cool temperate paleoclimate with a mean annual temperature (MAT) between 12 and 14° C and mean annual precipitation (MAP) between 1200 and 1300 mm yr-1. These integrated data sets also provide a better understanding of the stratigraphic development of the coastal plains.
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New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems
After initial breakthroughs in the discovery of fossil soils, or paleosols in the 1970s and early 1980s, the last several decades of intensified research have revealed the much greater role that these deposits can play in reconstructing ancient Earth surface systems. Research currently focuses on terrestrial paleoclimatology, in which climates of the past are reconstructed at temporal scales ranging from hundreds to millions of years, using paleosols as archives of that information. Such research requires interdisciplinary study of soils conducted in both modern and ancient environments. These issues and many others were discussed at the joint SEPM-NSF Workshop “Paleosols and Soil Surface Analog Systems”, held at Petrified Forest National Park.