Tectonic and denudational history of the Rennick Graben (North Victoria Land): Implications for the evolution of rifting between East and West Antarctica

摘要

The tectonic depression of the Rennick Graben (northern Victoria Land, Antarctica) is a key element for deciphering the Cenozoic separation history between East and West Antarctica and evolution of the West Antarctic rift system. The geometry, kinematics and timing of the boundary faults of the Rennick Graben are presented, on the basis of a detailed structural study of the major fault segments combined with apatite fission track data. The structural architecture of the Rennick Graben is controlled by distributed and partitioned right-lateral strike-slip faulting. Fission track data indicate that the last significant denudation stage of the Rennick Graben shoulders started from Eocene times, with increasing cooling and denudation since 40―50 Ma. A direct structural connection is then established between Cenozoic denudation and the activation of the dextral strike-slip regime in north Victoria Land during the Cenozoic. In this framework, the Rennick Graben is interpreted as a localized tectonic depression generated as a displacement accommodation area of the regionally sized dextral strike-slip shearing. The results of this study (1) invalidate the commonly assumed link between Mesozoic Ross Sea rifting and opening of the Rennick Graben; (2) argue against orthogonal rifting models for the Cenozoic evolution of the Ross Sea region; and (3) provide constraints to the modalities and timing of the separation between the East Antarctic craton and the West Antarctica extensional province.