Brittle faulting in the Prince Charles Mountains, East Antarctica: Cretaceous transtensional tectonics related to the break-up of Gondwana
Section snippets
Geologic setting and scope of study
The Lambert Glacier–Amery Ice Shelf drainage system represents the largest single ice stream flowing from the interior of East Antarctica (Fig. 1). It drains approximately one quarter of the entire East Antarctic ice sheet and forms a large ice surface depression in which the isolated peaks of the Prince Charles Mountains are exposed (Fig. 1a). The earliest geological expeditions to this region postulated that a graben-type structure (called the Lambert Graben) might underlie the Lambert
Fault structures—Prince Charles Mountains
Brittle faults found in the vicinity of Radok Lake generally form north to NNE trending fault planes that dip steeply (∼70–80°) to the west (Table 1, Fig. 2a). These faults cross-cut all earlier structural and intrusive features with the exception of alkaline mafic dykes (Stephenson and Cook, 1992) along the margins of which faulting appears to have been localised. The scale of faulting varies from discrete, narrow millimeter scale planes, to large brecciated gouge zones up to ∼0.5 m in width
Fault slip analysis
Orientation data from striated faults have been used in a number of studies to estimate the average stress state that best explains the observed brittle deformation Arthaud, 1969, Angelier and Mechler, 1977, Angelier, 1979, Angelier, 1984, Angelier, 1989, Angelier, 1990, Aleksandrowski, 1985, Oncken, 1988, Rocher et al., 2000. The calculation of palaeostress directions is based on the assumption that the direction and sense of the observed motion along a fault plane is parallel to one of the
Regional correlations
The other major study that presents kinematic data relating to brittle structures from the Prince Charles Mountains is that of Hofmann (1991). He presented both orientation and kinematic data from faults that define the eastern margin of the Amery Group Fig. 1, Fig. 6. Hofmann (1991) described two sets of faults. One set is similarly orientated to those observed at Radok Lake, trending north–northeast and dipping moderately to the west, while the second set trends east–ENE and dips moderately
Discussion
This study reports fault and striation orientation data from the Prince Charles Mountains–Prydz Bay region of East Antarctica. These faults generally trend north to NNE and dissect at high angles the east–west trending Archaean and Proterozoic rocks that form the basement to this region. The surface orientation of these faults is parallel with the subsurface regional scale structures identified geophysically Wellman and Tingey, 1976, Kurinin and Grikurov, 1982, Fedorov et al., 1982. Observed
Conclusions
Quartz- and calcite-bearing faults found in the Prince Charles Mountains represent the surface expression of deep crustal structures that define the Lambert Graben, a 700-km-long zone of thinned continental crust, which represents the most significant Mesozoic crustal structure in East Antarctica. These faults formed in response to a NW–SE-directed extensional stress field that lies oblique to the trend of both the recognised surface and subsurface structures. Deformation resulted in
Acknowledgements
Logistic support was provided by the Australian Antarctic Division while funding was from Australia Science Advisory Committee Grant 2131 awarded to CJLW. The expeditioners of 1995/96 and 1997/98 are thanked for their assistance during the summer programs, particularly Gary Kuen who made things happen in the southern Prince Charles Mountains. John Miller and Steve McLoughlin are also thanked for reading an earlier version of the manuscript, as are John Veevers and Dickson Cunningham whose
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