Dufek Massif, Pensacola Mountains

Fig. 8.6 The Patuxent Range of the Pensacola Mountains is separated from the Thiel Mountains by a distance of about 200 km that is covered by the Eiast Antarctic Ice Sheet. The only other mountains close to the Patuxent Range are the Pecora Esetupment and the Rambo Nunataks. The northern part of the Pensacola Mountains includes the Neptune Range, the Forrestal Range, and the Dufek Massif (Adapted from the Geologic Map of Antarctica in Craddock 1982)...

The Pensacola Mountains were discovered on January 13, 1956, during a transpolar reconnaissance flight by the US Navy. They were observed again on October 23, 1957, by Captain Finn Ronne of the US Navy and Dr. Edward C. Thiel during a flight from Ellsworth Station to the Dufek Massif. 

The northern Pensacola Mountains are dominated by the Dufek Massif which consists of a very large body of layered gabbro and ultramafic rocks of Jurassic age (Ford 1970 Ford and Kistler 1980). This body extends to the southeast across the Sallee Snowfield in Fig. 8.6 to the Forrestal Range where it covers the folded sedimentary rocks of Paleozoic age that also occur in the Neptune Range. The structure and origin of the Dufek Massif is presented in Chapter 13. 

The Argentina Range is an extension of the Pensacola Mountains along the coast of the Ronne Ice Shelf. This small mountain range consists of three clusters of nunataks located at about 82°20 S and 042°00 W which form the Schneider Hills, Mt. Ferrara, and the Panzarini Hills in Fig. 8.17. The Schneider Hills are separated from the Dufek Massif and the Forrestal Range of the Pensacola Mountains by the Support Force Glacier which channels the East Antarctic Ice Sheet into the Ronne Ice Sheet. 

Jurassic Ferrar Dolerite. Sills of the Ferrar Dolerite are not common elsewhere in the Pensacola Mountains except, of course, in the Dufek Massif where the gab-bros have been correlated with the sills of the Ferrar Dolerite. 

The Dufek intrusion is a layered deposit of mafic and ultramafic plutonic rocks that form the Dufek Massif and parts of Forrestal Range of the northern Pensacola Mountains (Schmidt and Ford 1969 Ford et al. 1977 ... 

The Cordiner Peaks are located about 15 km south of the southern end of the Dufek Massif (Fig. 13.41). This cluster of nunataks is composed of gently folded sedimentary rocks that characterize the Neptune Range of the Pensacola Mountains (Section 8.2.3) including the Gale Mudstone, the Dover Sandstone, and the sedimentary rocks of the Neptune Range of Paleozoic age (Schmidt and Ford 1969). These rocks were intruded by sills of the Ferrar Dolerite. 

Fig. 13.40 The Dufek intrusion in the northern Pensacola Mountains extends from the Dufek Massif across the Sallee Snowfield to the Forrestal Range. Geophysical surveys by Behrendt et al. (1974, 1979, 1980, 1981) indicate that the intrusion is a continuous tabular body that extends north about 250 km from the northern tip of the Dufek Massif. Ferris et al. (1998) questioned this extrapolation of the area of the Dufek intrusion and reduced it from about 50,000 to only 6,600 km. Even in that case, the area of the Dufek intrusion is exceeded only by the Bush veld Complex of South Africa (Adapted from Ford 1990)...

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