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Thermal evolution of the Sisters shear zone, southern New Zealand; Formation of the Great South Basin and onset of Pacific‐Antarctic spreading
Author(s) -
Kula Joseph,
Tulloch Andy J.,
Spell Terry L.,
Wells Michael L.,
Zanetti Kathleen A.
Publication year - 2009
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2008tc002368
Subject(s) - geology , shear zone , paleontology , cretaceous , gondwana , pacific plate , mylonite , geomorphology , seafloor spreading , thermochronology , subduction , structural basin , zircon , tectonics
The separation of Zealandia from West Antarctica was the final stage in the Cretaceous breakup of the Gondwana Pacific margin. Continental extension resulting in formation of the Great South Basin and thinning of the Campbell Plateau leading to development of the Pacific‐Antarctic spreading ridge was partially accommodated along the Sisters shear zone. This east‐northeast striking brittle‐ductile structure exposed along the southeast coast of Stewart Island, New Zealand, is a greenschist facies extensional shear zone that separates a hanging wall of chloritic, brecciated granites, and undeformed conglomerate from a footwall of mylonitic Carboniferous and Early Cretaceous granites. This complex structure exhibits bivergent kinematics and can be subdivided into a northern and southern segment. The 40 Ar/ 39 Ar thermochronology indicates that cooling of the shear zone footwall began at ∼94 Ma with accelerated cooling over the interval ∼89–82 Ma. Structural and thermochronological data indicate a spatial and temporal link between the Sisters shear zone, initial sedimentation within the offshore Great South Basin, extension of the Campbell Plateau, and initiation of the Pacific‐Antarctic spreading ridge.