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TitleApplication of seismic shothole drillers' log records to drift geochemical exploration and natural resource development
AuthorSmith, I R
Source38th annual Yellowknife Geoscience Forum, asbstracts of talks and posters; by Palmer, E; Northwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume vol. 2010, 2010 p. 59
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20110099
MeetingYellowknife Geoscience Forum; Yellowknife, NWT; CA; November 16-18, 2010
File formatpdf
ProvinceNorthwest Territories; Yukon
Subjectssurficial geology/geomorphology; geochemistry; economic geology; freezing ground; ground ice; drift prospecting; drift geochemistry; tills; till geochemistry
ProgramNorthern Pipelines, Environmental Geoscience
AbstractThe seismic shothole drillers' log project has undertaken the collection and digital rendering of all available archival data from Northwest Territories and Yukon held by the petroleum and geophysical exploration industries. The present database (~276,000 records) is being updated to a final ~350,000 records, and represents the extent of data holdings of 22 companies (102 companies/successors/data stewards have authorized release of joint-venture data). These formerly unutilized data have provided a wealth of regional baseline, near-surface (10-60 m) geoscience information that has become the foundation for new and original GIS-based reconstructions of: drift and till isopach (thickness) models, till facies, granular aggregate resources (sand and gravel), bedrock outcrop and subcrop, geohazards, muskeg thickness, massive ice and ground ice occurrences, permafrost extents and thicknesses, and bottomfast ice extents.
Drift geochemical exploration, or 'drift prospecting,' predominantly involves the regional sampling of unconsolidated glacial and/or fluvial sediments as a means of identifying bedrock-hosted economic mineral deposits. Successful application of this exploration technique requires detailed knowledge of the character of the unconsolidated sediment cover including sediment erosion-transport-depositional histories. The drillers¿ log records provide the most extensive archive of surficial geology in the central and western NWT and northern Yukon, extending across fifty-eight 1:250,000 map sheets, of which less than half have been, or are currently the subject of surficial geology mapping. In addition, the drillers¿ logs have been used to produce drift and till isopach models that identify regional drift dispersal/accumulation patterns including the influence that local topography has had on these. The drillers¿ logs have also been used to identify regional till facies. Tills predominantly derived from more local, shale-rich bedrock are typically distinguished in the drillers¿ log records as blue clay/silt-rich deposits, while tills comprised of more distal Canadian Shield-derived bedrock are recorded as brown sand-rich deposits. Understanding of these facies relationships and their relative extents is important to both designing effective drift sampling programs, and interpreting what can be disparate till geochemical signatures. The drillers' logs can also be used to identify specific drift exploration targets such as surface and subsurface sorted sediment deposits; often a difficult task in regions characterized by extensive organic and thick drift cover.
With respect to natural resource infrastructure development (e.g., roads, pads, pipelines), the drillers¿ log-derived geoscience reconstructions are likely to become a fundamental baseline geoscience resource used in infrastructure proposal design, environmental assessment, and construction. Examples of the application of drillers¿ log data is discussed in terms of identification of granular aggregate resources (gravel and sand, as well as quarriable bedrock outcrop and subcrop localities), and potential hazards to surface construction activities (e.g., buried ice, unfrozen sediments/water at depth, muskeg thicknesses).