Donnelly Member

Donnelly Member
Name	Donnelly Member
Type	Member
Age	Pleistocene
Period	Quaternary
Region	Yukon
Country	Canada

Donnelly Member

The Donnelly Member is a Pleistocene stratigraphic unit exposed in the Yukon and adjacent parts of Alaska and British Columbia. It has been described in regional syntheses by investigators associated with institutions such as the Geological Survey of Canada, the United States Geological Survey, and universities including the University of British Columbia, the University of Alaska Fairbanks, and the University of Toronto. Field research on the Donnelly Member has involved collaboration among specialists from the Royal Ontario Museum, the Canadian Museum of Nature, the Smithsonian Institution, the Natural Resources Canada laboratories, and academic departments like the Department of Earth and Planetary Sciences (Harvard University). Major mapping efforts have been incorporated into provincial programs led by the Government of Yukon and federal initiatives such as the Canada–United States Yukon River Basin studies.

Geology

The Donnelly Member occurs within Pleistocene successions that overlie older bedrock mapped by the Geological Survey of Canada and the United States Geological Survey in the Yukon–Tanana Upland and the Kluane Ranges. Stratigraphically it is associated with Quaternary frameworks developed by researchers at the International Union for Quaternary Research and regional compilations by the Canadian Quaternary Association and the Quaternary Research Association (UK). Structural control on the Donnelly Member exposures reflects tectonic provinces tied to the Cordilleran Orogeny and features like the Denali Fault and the Tintina Fault. Geomorphological context relates to Pleistocene glaciation events interpreted in light of studies from the Cordilleran Ice Sheet program, the Laramide Orogeny legacy, and regional paleoclimatic reconstructions by teams at the PAGES network and the National Oceanic and Atmospheric Administration.

Lithology and Stratigraphy

Lithologically, the Donnelly Member comprises sequences of unconsolidated sediments including tills, gravels, silts, and peat lenses documented by field crews from the Geological Survey of Canada, the Alaska Division of Geological & Geophysical Surveys, and academic groups from the University of Calgary and the University of Alberta. Grain-size analyses and sedimentary logging follow protocols from the Sedimentology Society and laboratory techniques standardized by the American Geophysical Union and the Society for Sedimentary Geology (SEPM). Stratigraphic correlations utilize radiometric data calibrated against chronologies developed by the International Commission on Stratigraphy and luminescence techniques refined at the Max Planck Institute for Evolutionary Anthropology and the University of Oxford Radiocarbon Accelerator Unit. Core records and outcrop descriptions are archived in repositories such as the Yukon Geological Survey and the British Columbia Geological Survey.

Depositional Environment

Interpretations of depositional environments for the Donnelly Member integrate concepts from glacial geology as applied in studies of the Cordilleran Ice Sheet, periglacial dynamics reported in literature from the Institute of Arctic and Alpine Research (INSTAAR), and fluvial analyses used by investigators at the USGS and the Geological Survey of Canada. Sedimentary features point to environments ranging from subglacial and proglacial settings to braided-river systems described in comparative studies of the Matanuska Formation and the Goldstream Formation. Paleohydrological reconstructions build on analogues from the Nisqually River basin and glacial lake investigations like those of Glacial Lake Missoula by researchers affiliated with the University of Montana.

Fossil Content

Fossil assemblages recovered from Donnelly Member deposits have been reported by paleontologists associated with the Canadian Museum of Nature, the Royal British Columbia Museum, and the Smithsonian Institution National Museum of Natural History. Macrofaunal remains include megafauna comparable to records from the Yukon Ice Patch and sites such as Bluefish Caves and the Old Crow Flats, with taxa similar to specimens curated in institutions like the Royal Ontario Museum and the American Museum of Natural History. Microfossil and palynological datasets were produced in laboratories at the University of Copenhagen and the University of Saskatchewan and interpreted following methods promoted by the Quaternary Research Association. Paleoecological interpretations reference analogues from Beringia studies and megafaunal research programs led by the Natural History Museum (London), the Paleontological Research Institution, and the Alaska Quaternary Center.

Age and Correlation

Age determinations for the Donnelly Member draw on radiocarbon dates, optically stimulated luminescence, and tephrochronology correlated with eruptions cataloged by the Global Volcanism Program and regional tephra frameworks established by teams at the University of Iceland and the Geological Survey of Canada. Chronostratigraphic placement uses Pleistocene subdivisions articulated by the International Commission on Stratigraphy and regional correlations with units like the Goldstream Formation and the Itcha Range deposits cited in publications by the Canadian Journal of Earth Sciences and the Quaternary Science Reviews. Comparative studies reference paleoenvironmental timelines from the Last Glacial Maximum reconstructions performed by researchers at the National Center for Atmospheric Research and the PAGES 2k Network.

Economic Significance

Economic interest in the Donnelly Member arises in contexts of aggregate resources, permafrost engineering, and mineral exploration coordinated with territorial agencies such as the Yukon Government Department of Energy, Mines and Resources and national programs from Natural Resources Canada. Engineering assessments follow standards from the Canadian Standards Association and practices used in northern infrastructure projects by consultants like Golder Associates and Stantec. Environmental management and land-use planning involve stakeholders including the Council of Yukon First Nations, the Yukon Environmental and Socio-economic Assessment Board, and federal partners such as the Department of Fisheries and Oceans (Canada).

Category:Geology of Yukon Category:Quaternary stratigraphy