| Summary: | Bibliography: pages [81]-85. Two new geologic profiles of McMurdo Sound have been constructed from seismic refraction data collected in the field seasons of 1980 and 1981. The 40 km east-west geologic profile located between the Strand Moraines on the west and Hut Point Peninsula on the east depicts five eastward dipping rock layers. The top layer has been identified as glacial—marine sediments that are Late Oligocene or younger in age. Below this are Cretaceous to Oligocene pre-glacial elastics. The third layer is believed to be comprised of sandstone that is correlative with the Beacon Supergroup. The fourth layer is crystalline basement. Below this is a lower crustal layer that has a probable granulite facies composition. The major structural feature, which is found towards the center of the profile, is a large, listric normal fault. Associated with this major fault are several subsidiary synthetic and antithetic faults. Movement along the faults in this region is believed to be no older than Late Oligocene. The 195 km north—south geologic model is located between the McMurdo Ice Shelf on the south and the NordenskJold Ice Tongue on the north. The depth to the mantle at the south end of the profile is 20.56 km. At the north end, the depth is 27.91 km. Apparent mantle dip along the profile is 2.2 degrees to the north. Calculated geologic dip along the north—south profile line is 36.3 degrees west towards the coast of Southern Victoria Land. The second part of this study emphasized identification of visible secondary arrival phases that could be picked from field records. For the east—west 1980 refraction data, the most persistent secondary refraction arrivals were S—waves from the basement or intrabasement refractor and P—waves from the pre-glacial bottom assorted clastic layer. For the north-south 1981 refraction data, the most persistent secondary refraction arrivals were P-waves from the glacial-marine top assorted clastic layer and P-waves from the Beacon Sandstone. M.S. (Master of Science)
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