| Summary: | Includes bibliographical references. Includes illustrations and maps. Seismic refractions were recorded from 21 stations in western McMurdo Sound during the Austral summer of 1979-1980. An interpretation of the geologic structure beneath the sound is made from fourteen of those stations. The stations in the study form a detailed profile roughly perpendicular to Victoria Land, east of Butter Pt. The geophysical model reveals that the basement complex which outcrops along the coast dips steeply to a depth of 2000 m only 11 km offshore. This is interpreted as a normal fault with a displacement of at least 1.8 km. The basement, Unit D in this report, has a mean velocity of 5.4 km/sec. and is interpreted to be an offshore extension of the metasediments outcropping on shore. A high velocity refractor (6.7 km/sec) below the basement may either be Ferrar Dolerite or an isolated body within the crystalline complex. Overlying the down dropped basement are three seismostratigraphic units. The lowest unit, unit C, having a velocity of 4.35 km/sec, may be a section of the Devoniam-Jurassic age Beacon Supergroup which outcrops in the Trans-antarctic Mountains. If this is true, then the Kukri Erosion surface developed on the basement surface has been doun-dropped 3000 m from its position in the Dry Valleys. These sediments are overlain by a unit having a velocity of 3.5 km/sec, Unit B, which may correlate with preglacial Oligocene sediments found at DSDP site 270 and may also be the same unit which is the source of Early Tertiary erratics found in the McMurdo Sound area. A thin (<200 m), discontinuous layer of Miocene to Pleistocene glacial material, Unit A, having a velocity of 2.0 km/sec, mantles the sea floor. M.S. (Master of Science)
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