Transantarctic Mountains
Contrasting Architecture and Dynamics of the
Transantarctic Mountains
TAM Home :: Pensacola-Pole Transect

Subglacial morphology and structural geology in the southern Transantarctic Mountains from airborne geophysics

Marcy B. Davis, M.S.The University of Texas at Austin, August, 2001 
Co-Supervisors: Donald D. Blankenship and Ian W. D. Dalziel

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The airborne survey extended from the Ross Ice Shelf, southward over the TAM along the 150ºW meridian and between the Scott and Reedy Glaciers then over the high plateau and through the South Pole.

Survey map of the TAM. The Pensacola-Pole survey area extended from the Ross Ice Shelf to the South Pole and into the eastern hemisphere and was flown during the 1998-1999 field season (SOAR RTZ8)
Survey map of the TAM. The Pensacola-Pole survey area extended from the Ross Ice Shelf to the South Pole and into the eastern hemisphere and was flown during the 1998-1999 field season (SOAR RTZ8)

Approximately 15,000 line km were flown and processed using finite difference migration techniques in a seismic processing software package (Focus 4.3). Subsequently, the ice and bed surfaces were picked along each line (using Schlumberger's Geoquest) and known geology was interpreted on the radar records where it exists. Ice-penetrating radar sounding coupled with a compilation of field geologic studies has proven to be a powerful technique for examining the architecture and structural geological relationships of the southern TAM.

Four distinct morphological provinces are identified along the length of the survey, these include: 1) the South Pole Basin and Plateau Province, with low relief features and up to 4 km of ice; 2) the Alpine Glaciated Province, with well-preserved U-shaped valleys that show a glaciation network that flowed opposite of contemporary glaciers; 3) the TAM Massif, which includes three subglacial blocks and the outcropping portion of the TAM; and 4) the TAM Front, a normal fault zone north of the TAM to Ice Stream A.


Ice-Penetrating radar profile showing the subglacial topography in the Alpine Glaciated Province

Ice-Penetrating radar profile showing the subglacial topography in the Alpine Glaciated Province. Note the U-shaped valleys which are approximately 5 km wide by 800 m deep

The southern TAM have a southward tilted block structure with the area of maximum uplift in a region 30-50 km wide from the Watson Escarpment, the highest part of the TAM in this area, southward and is bounded by NW-SE-trending normal faults on both the north and south sides. Down-to-the-north normal faults north of the Watson Escarpment topographically downdrop the TAM from >3000 m to sea level over ~50 km and facilitate the development of the Leverett Glacier and Ice Stream A. The primary structural trend between the Scott and Reedy Glaciers is NW-SE, parallel to the TAM. Faults oriented obliquely to the TAM break the area of maximum uplift into three NNW-SSE trending blocks with range-parallel horst and graben features superimposed. One of these faults may control the eastern side of Scott Glacier. Structural relationships across the Watson Escarpment suggest that the southern TAM are a result of upward block faulting along the TAM Front rather than a result of regional upwarping.

Gridded subglacial topography showing faults along the Transantarctic Mountain Front as identified using ice-penetrating radar profiles. Only a small portion of the interpreted map is shown here

Gridded subglacial topography showing faults along the Transantarctic Mountain Front as identified using ice-penetrating radar profiles. Only a small portion of the interpreted map is shown here.