摘要：Wc employed a commercial wircline drill rig to investi ga te the subgl acial
conditions of Black Rapids Glac ier, a well-studi ed surge-type glacier in the central Al as ka
Range. The four ma in goa ls were: to assess the capabilities of the commercial drilling indu try
for sampling subglacialmaterial, to investigate the basa l morphology, to determine the subglacial geology a nd to emplace borehole instruments. The drilling was do ne in an area where
seasonal and secul a r vari ations in speed are large, a nd where seismic studies suggested the
presence of a till layer. Four holes were drill ed at three locations to a max imum depth of
620 m. Three holes yielded samples of basal ice and till, although recover y of th e latter was
generall y poor. Bedrock was sampled in one or possibly two of the holes. In the area sampl ed,
the glacier is underlain by a till layer some 4- 1 m thi ck, confirming the seismic in te rpreta ti on.
It consists of a sand y matrix at least 20- 30% of which comprises larger c1 asts. Limited samples
of the matrix indicate that near the top of th e till the porosit y is 40%, and that some of the pore
water is frozen. Geologic studies suggest that the drilling area lies to the north of th e De nali
Fault, a maj or tec tonic boundary followed by the glacier, and th at most of the till is loca ll y
derived with tra nsport distances of <2 km.
