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Geosciences Research in East Antarctica (088888E–6088888E): Present Status and Future Perspectives

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Geosciences Research in East Antarctica (088888E–6088888E): Present Status and Future Perspectives Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Geosciences research in East Antarctica (088888E–6088888E): present status and future perspectives M. SATISH-KUMAR1, T. HOKADA2, T. KAWAKAMI3 & DANIEL J. DUNKLEY2 1Institute of Geosciences, Shizuoka University, Oya 836, Suruga-ku, Shizuoka 422-8529, Japan (e-mail: [email protected]) 2National Institute of Polar Research, Kaga, Itabashi-ku, Tokyo 173-8515, Japan 3Department of Geology and Mineralogy, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan Abstract: In both palaeoenvironmental and palaeogeographical studies, Antarctica plays a unique role in our understanding of the history of the Earth. It has maintained a unique geographical position at the South Pole for long periods. As the only unpopulated continent, the absence of political barriers or short-term economic interests has allowed international collaborative science to flour- ish. Although 98% of its area is covered by ice, the coastal Antarctic region is one of the well- studied regions in the world. The integrity and success of geological studies lies in the fact that exposed outcrops are well preserved in the low-latitude climate. The continuing programme of the Japanese Antarctic Research Expedition focuses on the geology of East Antarctica, especially in the Dronning Maud Land and Enderby Land regions. Enderby Land preserves some of the oldest Archaean rocks on Earth, and the Mesoproterozoic to Palaeozoic history of Dronning Maud Land is extremely important in understanding the formation and dispersion of Rodinia and subsequent assembly of Gondwana. The geological features in this region have great signifi- cance in defining the temporal and spatial extension of orogenic belts formed by the collision of proto-continents. Present understanding of the evolution of East Antarctica in terms of global tec- tonics allows us to visualize how continents have evolved through time and space, and how far back in time the present-day plate-tectonic regime may have operated. Although several funda- mental research problems still need to be resolved, the future direction of geoscience research in Antarctica will focus on how the formation and evolution of continents and supercontinents have affected the Earth’s environment, a question that has been addressed only in recent years. The formation and evolution of continents has mid-ocean ridges since the Mesozoic (Fig. 1 inset), always been an intriguing topic in Earth Science with the exception of the Antarctic Peninsula, studies. The complexity of continental evolution which is its only active convergent plate margin largely results from the protracted and recurring with transform faults dividing the Antarctic Plate nature of geological processes that have taken and Scotia Plate. This means that the Antarctic place in the continental lithosphere. Decoding bil- Plate is currently expanding relative to the surround- lions of years of complex history recorded in the ing plates. This is a feature that is at variance continental crust is a daunting task. However, geol- with most other lithospheric plates, and makes the ogists have made great progress in understanding Antarctic continent exceptionally stable, and isolated the processes involved in continental formation from all regional tectonic events during the Mesozoic and their evolution through time. The Antarctic and Cenozoic. Consequently, the older geological continental lithosphere is an important crustal frag- history of East Antarctica can be considered as one ment that provides us with an abundance of infor- of the least overprinted records of crustal evolution mation on the formation of continents, and the in the Earth’s history, preserved in a natural ‘cold temporal and spatial relationships involved in the storage’. Its geological history records the formation assembly and dispersion of supercontinents. of early Archaean protocontinents, and continues The significance of Antarctica lies not only in its throughout the Proterozoic, until the amalgamation unique geographical position, whereby it has gained of East and West Gondwana at the beginning of the due importance in palaeoenvironmental studies, but Palaeozoic. Therefore, the geological record in East also in its geological stability since incorporation in Antarctica is an invaluable record of the origin and the supercontinent Gondwana at the beginning of evolution of continents and supercontinents, and for the Phanerozoic Era. This is primarily because the understanding the secular changes in metamorphic Antarctic lithospheric plate has been surrounded by conditions in orogenic belts (Brown 2007). From:SATISH-KUMAR, M., MOTOYOSHI, Y., OSANAI, Y., HIROI,Y.&SHIRAISHI, K. (eds) Geodynamic Evolution of East Antarctica: A Key to the East–West Gondwana Connection. Geological Society, London, Special Publications, 308, 1–20. DOI: 10.1144/SP308.1 0305-8719/08/$15.00 # The Geological Society of London 2008. 2 Downloaded from http://sp.lyellcollection.org/ M. SATISH-KUMAR byguestonOctober1,2021 ET AL. Fig. 1. Index map of geographical regions and localities in East Antarctica corresponding to the contributions in this Special Publication. Inset shows a topographic map of Antarctica and surrounding oceans. Red indicates topographically elevated places; blue indicates ocean floor. (Data source: Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2006, 2-minute Gridded Global Relief Data (ETOPO2v2), http://www.ngdc.noaa.gov/mgg/fliers/ 06mgg01.html). Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 GEOSCIENCES RESEARCH IN EAST ANTARCTICA 3 It is beyond the scope of this book to update the (Hoffman 1991). However, subsequent years have reader with the voluminous literature that has been seen a steady increase in the volume and detail of produced in the past few decades on the geology of tectonic and geochronological research from all East Antarctica. However, we make an attempt to areas of East Antarctica that has shown a more integrate the results of some recent studies from complex story of the diverse origins of various the eastern region of the Antarctic continent, sectors of the East Antarctic margin, challenging where the Japanese Antarctic Research Expedition the ‘shield’ paradigm. Late Mesoproterozoic meta- (JARE) has, over the past 50 years, conducted morphic terranes located along the Antarctic coast extensive investigations. We introduce the general at 308W–358E (the 1100–1000 Ma Maud Belt), geology of the region and summarize what is 458E–708E (the 1000–900 Ma Rayner Complex) known to date, and in the process introduce the con- and 1008E–1208E (the 1300–1100 Ma Wilkes Pro- tributions in this volume. The contributions in the vince), were found not only to differ subtly in age, volume are related to the outcrops that are situated but also to be separated by areas of c. 600–500 Ma between 08E and 608E in Dronning Maud Land and moderate- to high-temperature metamorphism and Enderby Land of East Antarctica (Fig. 1). In tectonism at Lu¨tzow-Holm Bay (408E) and Prydz addition, this paper also attempts to lay down ‘a Bay (708E; Fitzsimons 2000). Thus, instead of repre- vision for future’, based on the current status of senting a continuous marginal mobile belt, each of geological knowledge. the Mesoproterozoic metamorphic terranes could be correlated with discrete mobile belts in South Africa (Namaqua–Natal Belt), India (Eastern East Antarctica: an integral part Ghats) and South Australia (Albany–Fraser of Gondwana Orogen). Furthermore, it was recognized that a large section of the Maud Belt was reworked by The challenge of developing tectonic scenarios for late Neoproterozoic metamorphism and defor- the formation of the ice-covered Antarctic continent mation that could be correlated with the extensive is uniquely difficult; no other continent presents East African Orogen, produced by the amalgamation such a blank sheet on which geological terranes of East and West Gondwana (Jacobs et al. 2003a). can be drawn by inference only. Virtually all under- Recognition of unrelated pre-Rodinian cratons in standing of the geological architecture is drawn East Antarctica was also achieved, with the corre- from intensive studies of coastal outcrops and lation of the Mawson continent and the Gawler mountain ranges near the continental margins. A Craton in South Australia (Fanning et al. 1996), full 1808 arc of coastline, encompassing East and the geochronological characterization of Antarctica, provides an array of outcrops that Archaean terranes south of a c. 550 Ma suture zone almost exclusively share a Precambrian origin. in the southern Prince Charles Mountains adjacent This reflects the intracontinental nature of the East to Prydz Bay (Boger et al. 2001; Mikhalsky et al. Antarctic coast in the supercontinent Gondwana, 2001, 2006; Phillips et al. 2006). after its formation at the end of the Proterozoic. New studies (e.g. Kelsey et al. 2008) continue to The stability of the continent throughout the develop the latest paradigm of the assembly of East Phanerozoic has also led to the concept of an East Antarctica from disparate continental bodies during Antarctic Shield, one of the large areas of crato- the late Neoproterozoic formation of Gondwana. In nized crust on Earth. The ‘shield’ concept also particular, the complexity of crustal development in influenced tectonic interpretations of coastal the sector between 08E and 708E, namely Dronning geology
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