Kinematic history of western Marie Byrd Land, West Antarctica: direct evidence from Cretaceous mafic dykes
Christine S. Siddoway, Louis C. Sass, III, Richard P. Esser, 2005. "Kinematic history of western Marie Byrd Land, West Antarctica: direct evidence from Cretaceous mafic dykes", Terrane Processes at the Margins of Gondwana, A. P. M. Vaughan, P. T. Leat, R. J. Pankhurst
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Intracontinental deformation occurred in West Antarctica during the final stages of plate convergence along the Cretaceous Gondwana margin. In western Marie Byrd Land, 115 Ma to 95 Ma A-type granitoids and mafic dykes record a change in plate kinematics. The magmatism typically is viewed as a record of extension leading to orthogonal break-up between New Zealand and Marie Byrd Land by c. 67 Ma. This paper presents new kinematic and 40Ar/39Ar age data for a mafic dyke array in the Ford Ranges, a region >1000 km2 dominated by plutonic and metamorphic bedrock. The mean dyke trend of N16W corresponds to a maximum finite strain axis orientated N74E, highly oblique to the N58E-trending margin and to on-land crustal structures defined from airborne geophysics. 40Ar/39Ar emplacement ages for most dykes fall between 114 Ma and 97 Ma, coeval with emplacement of a gneiss dome at 101-96 Ma and with development of mylonitic shear zones at 100-95 Ma in coastal western Marie Byrd Land. The oblique orientation of maximum finite strain with respect to large faults, geophysical lineaments and the rifted margin of western Marie Byrd Land is consistent with transcurrent tectonics along this segment of the Gondwana margin at c. 100 Ma.
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Terrane Processes at the Margins of Gondwana
The Australide orogen, the southern hemisphere Neoproterozoic to Mesozoic terrane accretionary orogen that forms the palaeo-Pacific margin of Gondwana, is one of the largest and longest-lived orogens on Earth. This book brings together a series of reviews and multidisciplinary research papers that comprehensively cover the Australides from the Tasman orogen of eastern Australia to the Neoproterozoic and Palaeozoic orogens of South America, taking in New Zealand and Antarctica along the way. It deals with the evolution of the southern Gondwana margin, as it grew during a series of terrane accretion episodes from the late Proterozoic through to final fragmentation in mid-Cretaceous times. Global perspectives are given by comparison with the Palaeozoic northern Gondwana margin and documentation of world-wide terrane accretion episodes in the Late Triassic-Early Jurassic and mid-Cretaceous. The Tasmanides of eastern Australia, and the terrane histories of New Zealand and souther South America are given comprehensive up-to-date reviews.