Virtual Geomagnetic Poles

Measurements of the position of the virtual geomagnetic pole (VGP) have supported the hypothesis that the Rb-Sr and K-Ar dates of certain flows of the Kirkpatrick Basalt in the Mesa Range were lowered by 

The apparent duration of the remagnetization event and the high precision of the mean direction from the Bowers Supergroup are most consistent with locking in of the remanence during the Cretaceous normal polarity superchron. 

A study of the paleomagnetism by Delisle (1983) of the basalt and dolerite in the Litell Rocks provided additional evidence for a Cretaceous thermal event. Skinner et al. (1981) who described these rocks in the field, considered them to be representatives of the Ferrar Group of Middle Jurassic age, although Kreuzer et al. (1981) reported Cretaceous K-Ar dates between 90 and 120 Ma for specimens that appeared to be hydrothermally altered. Three samples of basalt from the Litell Rocks measured by Delisle (1983) indicated a well-defined Cretaceous pole position. Therefore, Delisle (1983, p. 149) concluded that  

Additional measurements of the paleomagnetism by Delisle and Fromm (1984, 1989) confirmed that the position of the VGP of Ferrar Dolerite sills in the Rennick Graben deviates significantly from its position during the Jurassic at 55°S and 220 E. The VGP reported by Delisle and Fromm (1989) for a dolerite sill on Roberts Butte located west of the Rennick Graben does not coincide with the Jurassic VGP but matches the Cretaceous VGP of the Litell Rocks obtained by Defisle (1983). Based on this new evidence Delisle and Fromm (1989, p. 149) concluded that  

The discovery of a unit on Roberts Butte with a paleomag-netic record very similar to that of the basaltic flow at Litell Rocks. is additional evidence in favor of the assumption of a thermal event in northern Victoria Land during 

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Robinson and Splettstoesser (1986) speculated that the Transantarctic fault zone, which separates East and West Antarctica, is the border between two lithospheric plates which were placed in juxtaposition in the course of the break-up of Gondwana. This hypothesis was supported by Scharnberger and Scharon (1972) who reported that the virtual geomagnetic poles derived from igneous rocks indicate that East and West Antarctica were originally located on different lithospheric plates. 

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