Upper Triassic Miers Bluff Formation of the Livingston Island,Antarctica and its Stratigraphical Correlations with Adjacent Areas
SHEN Yan bin 1) , DENG Xi guang 2) , OUYANG Shu 1) , ZHENG Xiang shen 2) , and LIU Xiao han 2) ( 1)Nanjing Institute of Geology and Palaeontology, the Chinese Academy of Sciences, Nanjing 210008; 2)Institute of Geology and Geoph
The Miers Bluff Formation (MBF), cropping out at Hurd Peninsula on Livingston Island, consists mainly of greywacks, mudstones, siltstones and pebbly mudstones, attaining a thickness of about 3000 m. The strongly deformed and low graded metasedimentary sequences are interpreted to be turbidite deposits of submarine fan. It is composed of, in ascending order, the Johnsons Dock Member, the Napier Peak Member and possibly the Moores Peak breccias. The age of the formation is poorly constrained ranging from late Paleozoic to early Mesozoic due to lack of identifiable fossils. Plant microfossils have been found from the MBF, including a total of about 45 species (forma) referred to 37 genera of miospores. The sporadic occurrence of Aratrisporites and Classopollis as well as the absence of bisaccate striatiti indicates that the age of the MBF should not be older than Noirian and possibly ranges from Norian to Rhaetian. Abundant organic matter including rich wood fragments (tracheids) in the MBF appears to show that the sedimentary site was not far apart from the land. The luxuriant parentflora with diverse pteridophytes seems to indicate a warm and humid climate. The MBF may be synchronous with those turbidite sequences represented by such formations as the Hope Bay, the Paradise Harbour and the Cape Legoupil of the Antarctic Peninsula and the Greywake Shale of South Orkney Islands, the Portranca Formation in Chile as well as the upper Torlesse Complex in New Zealand. All of these might have been contemporaneously deposited under similar tectonic style just prior to the break up of Gondwana in earlier Jurassic times.