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QUATERNARY GEOLOGY AND DRIFT PROSPECTING STUDIES IN THE NORTH CENTRAL NECHAKO PLATEAU ( 93 F AND K )

This paper provides an overview of Quaternary geology and drift prospecting studies conducted in the Nechako River and Fort Fraser 1:250 000 map areas (NTS 93 F and K, respectively) by the British Columbia Geological Survey in 1998. Research efforts were concentrated in the Tetachuck Lake (93 F/5), Marilla (93 F/12) and Pendleton Bay (93 K/12E) 1:50 000 NTS map areas (Figure 1). This work included surficial geology mapping, Quaternary stratigraphy and landslide hazard studies in the Tetachuck Lake and Marilla map areas, and till geochemistry and ice flow studies on all three map sheets. These investigations are part of the Nechako National Mapping Project, coordinated by the Geological Survey of Canada and the British Columbia Geological Survey (MacIntyre and Struik, 1999). Summaries of results of associated Quaternary geology and regional till geochemistry surveys previously conducted in parts of the Nechako Plateau were provided by Levson and Giles (1997) and Levson et al. (1997a,b, 1998). A more detailed description of surficial geology mapping and Quaternary studies in the Marilla map area is provided by Mate and Levson (1999). The main objectives of the Quaternary geology component of this work are to understand and map the distribution of surficial deposits, decipher the glacial history and ice-flow patterns, locate areas most suitable for conducting drift exploration programs, and provide data to aid in interpreting till geochemical results. Procedures used include compilation of existing surficial geology data, interpretation of air photographs, field checking, till sampling, and stratigraphic and sedimentologic investigations of Quaternary exposures. Ice-flow history was largely deciphered from measurement of the orientation of crag-and-tail features, flutings, drumlins and striae. The main objectives of the drift prospecting component of this study are to collect regional till geochemical samples, conduct case study investigations around known mineral occurrences, evaluate geochemical dispersal processes and locate mineralized erratics in surficial materials. Procedures used for this work including field methods, types of data collected, laboratory analyses and quality control procedures, are described in detail by Levson and Giles (1997).