Elsevier

Tectonophysics

Volume 367, Issues 3–4, 12 June 2003, Pages 173-186
Tectonophysics

Brittle faulting in the Prince Charles Mountains, East Antarctica: Cretaceous transtensional tectonics related to the break-up of Gondwana

https://doi.org/10.1016/S0040-1951(03)00125-2Get rights and content

Abstract

The Lambert Glacier–Amery Ice Shelf occupies a narrow NNE–SSW-orientated fault-bound depression referred to as the Lambert Graben. Deep faults associated with this structure are recognised geophysically, and are interpreted to extend at least 700 km inland from the Antarctic coast. Kinematic and palaeostress data from quartz- and calcite-bearing faults, inferred to represent the surface expression of these deeper structures, suggest that a single faulting event occurred in response to NW–SE-directed extension, oblique to the axis of the graben. The bulk of the movement along these faults was dextral strike slip, accommodating components of both normal and reverse offset. In the northern Prince Charles Mountains, these faults disrupt the Permo-Triassic Amery Group and juxtapose it against Proterozoic basement. Equivalent strike-slip faults in the southern Prince Charles Mountains produce dextrally offset tectonic boundaries and metamorphic isogrades across the Lambert Glacier. The similarity in orientation between the palaeostress field calculated for these faults and the Cretaceous divergence vector between India and Antarctica strongly supports the inference that faulting was of Cretaceous age, and 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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