Geological and laboratory analysis of rock samples from the Ruppert Coast-Hobb Coast, Marie Byrd Land, Kohler Range and Bear Peninsula to understand the Mesozoic Pacific ocean during Gondwanaland breakup

Prior to the breakup of Gondwanaland there was an entire southern rim to the Pacific extending from New Calendonia through New Zealand, West Antarctica to Patagonia. Understanding the Mesozoic tectonics of West Antarctica is pivotal to understanding much of the geology of New Zealand and southern South America. A joint collaboration between NZARP, BAS and the USAP undertook fieldwork over three field seasons.The first field season involved the examination and sampling of all available basement outcrops in the Ruppert Coast-Hobb Coast area. The second season sampled in the Pine Island Bay area which lies on the boundary between the Marie Byrd Land and Thurston Island crustal blocks. The party was based on the US Coast Guard icebreaker 'Polar Sea' and employed the ship's helicopter and small boats to gain access to all available outcrops (Mt Siple, Cape Felt, Pine Island Bay and associated islands, Thurston Island and Peter I Island). The third and final season areas in the Kohler Range, Bear Peninsula and the basement of the Murphy volcano were studied and sampled with approximately 3000lbs of rock collected for analysis. Tracing the nature and timing of the break up process during the last 100 million years in Marie Byrd Land will contribute to the understanding of the geology of New Zealand, particularly the Campbell Plateau and the Chatham Rise. Detailed laboratory analysis of major elements, trace elements, isotope geochemistry, geochronology by the Rb/Sr, U/Pb, and Ar40/Ar39 methods, and paleomagnetism were completed on rock samples. Because of the bad weather and difficult access, the geology of Marie Byrd Land was not well know but it is vital for understanding the southern margin of the Mesozoic Pacific ocean and the pattern of events during breakup of the Pacific sector of Gondwana.