Cenozoic deformation in the George V Land continental margin (East Antarctica)
Introduction
George V Land is located between approximately 140°E and 155°E on the East Antarctic margin (Fig. 1, Fig. 2), adjacent to the Wilkes–Adelie Land segment in the west and Oates Land to the east.
The depth of the continental shelf off the George V Land margin (Fig. 1) averages 500 m and generally increases shoreward from the shelf break. The inner-middle shelf contains the > 1000 m deep Mertz–Ninnis trough, also known as George V Basin. It is NE–SW oriented, and dips towards to the Mertz Glacier floating ice tongue. The basin is asymmetric in cross section and is steep-sided towards the coast, shoaling towards the northwest.
The landward side of the shelf near the coast is cut by three small topographic basins, seaward of Buchanan, Watt and Commonwealth Bays, oriented perpendicularly to the Mertz–Ninnis Trough (Fig. 1). The sedimentary sequence overlying the acoustic basement is generally dipping toward the north.
The continental slope extends from the shelf break down to about 2000 m water depth and it is deeply incised by canyons and wide channels (Fig. 1). In the continental rise, between 2500 and 3500 m of water depth, these channels are bound by north–south elongated, asymmetrical, sediment mounds, with relief of up to 1000 m, decreasing toward the ocean (Escutia et al., 2000, De Santis et al., 2003, Donda et al., 2003).
The George V continental margin area has been of general interest to several international surveys (USA, France, Japan and Australia). However previous survey coverage in the area is mostly restricted to widely spaced regional transects. The first offshore program was undertaken through the so called “Operation Deep Freeze” in 1979 (Domack et al., 1980). Several other surveys followed: the TH82 cruise, conducted by the Japan National Oil Corporation (Tsumuraya et al., 1985, Tanahashi et al., 1987); the IFP cruise, conducted by Institut Francais du Petrol (Wannesson et al., 1985), the USGS cruise, conducted by the US Geological Survey (Eittreim and Smith, 1987) and the AASOPP cruises, conducted by Geoscience Australia (Stagg et al., 2004).
The region of the George V Land margin was the target of the WEGA (WilkEs basin GlAcial history) multichannel seismic survey (Fig. 1). A coring program, together with a 3.5 kHz and Chirp subbottom survey was also conducted in the frame of the WEGA cruise, to image and sample sediment from the continental shelf, slope and rise of the George V Land continental margin. The survey aimed to study the sedimentary sequences of this sector of the East Antarctic margin, which appears to be strictly related to the glacial history of the Wilkes Basin, one of the largest East Antarctic subglacial basins (Drewry, 1976; Fig. 2). An additional outcome of the WEGA survey is that it extended seismic data coverage into the shallow continental shelf for the first time in this region. The coastal polynya of the George V Land is one of the few places of the East Antarctic margin where the oldest sedimentary section can be studied with the existing technology, because most of the East Antarctic continental shelf is covered by permanent, thick sea and terrestrial ice. Therefore even though the WEGA survey was not designed for investigating tectonic setting, the multichannel seismic data collected near the George V Land coast, where the oldest sediment section is shallowest, provide new evidence to highlight the structural and stratigraphic style of the rift phases between Australia and Antarctica and post-rift tectonic processes in the inner continental shelf.
These considerations are particularly relevant as the Mertz-Ninnis trough is located near the area of transition between the extensionally-dominated Wilkes Land–Great Australian Bight Basin conjugate margins and the transtensionally-dominated Otway Basin–South Tasman Rise–Oates Land conjugate margins.
The main parameters related to data acquisition and processing are listed in Table 1, Table 2. Key profiles W04, W05 and W06 were also processed by applying a wave equation migration, in order to best image the geometry of the tectonic and morphologic features.
Section snippets
Antarctica–Australia geological and geodynamic setting
Australia and Antarctica were once connected and, before breakup, they represented the conjugate parts of the northwest–southeast Southern Rift System (Stagg et al., 1990). It was active from the Late Jurassic to the Late Cretaceous, with the Wilkes Land located near the centre of the rift (Willcox & Stagg, 1990, Colwell et al., 2003). Several evidences of geological correlations of the Australia–Antarctica pre breakup fit have been provided, some of which are based on the age and style of
The George V Land continental shelf tectonic features
The analysis of the multichannel seismic profiles collected in the framework of the WEGA cruise highlights that two main structural phases affected the basement and its sediment cover in this sector of the George V Land continental shelf: a first tectonic phase that caused the formation of extensional grabens; a second tectonic phases that caused partial inversion of previous structures and sediment deformation.
The George V Land continental rise tectonic features
Dyke-like intrusion faults characterise the acoustic basement beneath the continental rise between 143°E and 144°E, as shown by multichannel seismic profiles collected in previous cruises (Eittreim and Smith, 1987) and the Australian AASOPP cruise (Stagg et al. 2004) with deeper penetration than the WEGA data. The WEGA seismic profiles also reveal the occurrence of cone-like structures characterised by convex reflectors and diffractions (Fig. 14). The reflectors onlapping and overlying these
Structural interpretation
- 1)
The extensional grabens that formed in the first tectonic phase are interpreted to be related to the Mesozoic phase of rifting between Antarctica and Australia. This is consistent with the lower Cretaceous (Aptian) age of the in-situ siltstone sample recovered from the oldest strata infilling these graben system and onlapping the basement along the coast, between the Mertz and Ninnis glacier (Domack et al., 1980). Brown lignites of Cretaceous age were also dredged west of the Mertz Glacier (
Relationship between the Southern Ocean geodynamic evolution and the superposed post-rift tectonics in the George V Land margin
The sector from Wilkes Land to Oates Land (105°–160°E) was formed during the separation of Australia and East Antarctica, culminating with the sea floor spreading in the late Cretaceous. Geologically the margin can be divided in two broad zones: one from the western Wilkes Land to the Terre Adélie, which formed predominantly in an orthogonal extensional setting involving the margins of western central Australia and East Antarctica; and the other off George V Land and Oates land, which formed in
Conclusions
The analysis of the multichannel seismic data collected in the George V Land margin highlights the importance of this sector of the Southern Ocean as it is located near the area of transition between the extensionally-dominated Wilkes Land–Great Australian Bight Basin conjugate segment of the Australian–Antarctic Rift and the transtensional, strike-slip kinematics of the Otway Basin–South Tasman Rise–Oates Land segment. For the first time the occurrence of rift and post-rift tectonic structures
Acknowledgments
The WEGA cruise was funded by Italian Programma Nazionale di Ricerche in Antartide (PNRA) and Australian National Antarctic Research Expeditions (ANARE) agencies (Brancolini and Harris, 2000). This work was funded by the PNRA under the WEGA and MOGAM projects. We thank the Institute Française du Pétrole and United Geological Survey for kindly providing access to the seismic data throughout the Antarctic Seismic Data Library System. We would like to thank Belinda Brown for her input in an early
References (63)
- et al.
A tectonic model of the Antarctic Gondwana Margin with implications for Southeastern Australia: isotopic and geochemical evidence
Tectonophysics
(1991) - et al.
New insights into Quaternary glacial dynamic changes on the George Vth Land continental margin (East Antarctica)
Quaternary Science Reviews
(2006) - et al.
A revised identification of the oldest sea-floor spreading anomalies between Australia and Antarctica
Earth and Planetary Science Letters
(1982) - et al.
Seismic stratigraphy and sediment distribution on the Wilkes Land and Terre Adélie margins
East Antarctica, Marine Geology
(2007) - et al.
Seismic facies and sedimentary processes on the continental rise off Wilkes Land (Antarctica): the role of bottom currents
- et al.
Seismic stratigraphic evidence of ice-sheet advances on the Wilkes Land Margin of Antarctica
Sedimentary Geology
(1995) - et al.
Thrust structures of the Ross/Delamerian orogenies in the northern Victoria Land (Antarctica) and the Glenelg–Kanmantoo complexes (southeastern Australia) and their implications on Gondwana reconstructions
- et al.
Deep-water Otway Basin: a new assessment of the tectonics and hydrocarbon prospectivity
APPEA Journal
(2000) - et al.
Breakup between Australia and Antarctica: a brief review in the light of new data
Tectonophysics
(1985) - et al.
Australia and Antarctica: precise correlations of Palaeoproterozoic terrains
Cenozoic tectonic lineaments of the Terra Nova Bay region
Global and Planetary Change
Cenozoic geodynamics of the Ross Sea region, Antarctica: crustal extension, intraplate strike-slip faulting, and tectonic subsidence
Journal of Geophysical Research
Intraplate strike-slip deformation belts
Geological Society of London Special Publication
The Mertz Shear Zone (George V Land): implications for Australia/Antarctica correlations and East Antarctic Craton/Ross orogen relationships
Terra Antartica Reports
Geology of deep-water margin of East Antarctica between Queen Mary and George V Lands
The structure of the continental margin off Wilkes Land and Terra Adélie Coast, East Antarctica
Leg 188 synthesis: transitions in the glacial history of the Prydz Bay region, East Antarctica, from ODP drilling
Aeromagnetic anomaly investigations along the Antarctic Coast between Yule Bay and Mertz Glacier
Terra Antartica
Seismo-stratigraphic analysis of the Wilkes Land continental margin (East Antarctica)
Deep Sea Research Special Part II
Lower Cretaceous sediment from the Antarctic continental shelf
Nature
Preliminary stratigraphy for a portion of the Wilkes Land continental shelf, Antarctica: evidence from till provenance
Sedimentary basins of the east Antarctic craton from geophysical evidence
Tectonophysics
Seismic sequences and their distribution on the Wilkes Land margin
Correlations between Tasmania and the Tasman–Transantarctic Orogen: evidence for easterly derivation of Tasmania relative to mainland Australia
Geology
Morphology and acoustic character of the Antarctic Wilkes Land turbidite systems: ice-sheet sourced versus river-sourced fans
Journal of Sedimentary Research
Cenozoic East Antarctic ice sheet history from the Wilkes Land sediments
et al.The Role of Intraplate Stress in Tertiary (and Mesozoic) Deformation of the Australian Continent and Its Margins: a Key Factor in Petroleum Trap Formation
Exploration Geophysics
Proceedings of the Ocean Drilling Program, Initial Reports, 189
Cited by (6)
Depositional and erosional signatures in sedimentary successions on the continental slope and rise off Prydz Bay, East Antarctica– implications for Pliocene paleoclimate
2020, Marine GeologyCitation Excerpt :The IODP Exp. 318, the IMAGE CADO and other projects revealed that the levees of the Jussieu Canyon preserve an incredible paleoceanographic archive of bottom water Cenozoic record (De Santis et al., 2010; Patterson et al., 2014, Jimenez-Espejo et al., 2020; Wilson et al., 2018; Smith et al., 2020). Our analysis suggest that such a similar record can be potentially obtained also from the levees of the Wild Canyon and provides the basis for a new IODP proposal.
Australian-Antarctic breakup and seafloor spreading: Balancing geological and geophysical constraints
2019, Earth-Science ReviewsCitation Excerpt :Fewer data are available over the offshore area in the conjugate George V Land section of the Antarctic margin. However, seismic profiles from the George V Basin (De Santis et al., 2010) show evidence for two phases of deformation, with the development of (likely Cretaceous) extensional grabens followed by a phase of transpressional/strike-slip deformation of Palaeocene or Eocene age. Some Australian-Antarctic reconstructions model an overlap of the Tasmania and Cape Adare region COTs (Fig. 8) at the expense of a good fit between Broken Ridge and the Kerguelen Plateau.
From Greenhouse to Icehouse at the Wilkes Land Antarctic Margin: IODP Expedition 318 Synthesis of Results
2014, Developments in Marine GeologyCitation Excerpt :These results are consistent with the suggestion that near-field processes such as local sea-level change influence the equilibrium state obtained by an ice-sheet grounding line. These results are also consistent with two reported tectonic deformation phases of shelf strata below the WL-U3 on the George V Land coast (De Santis, Brancolini, Donda, & O’Brien, 2010). A first extensional phase resulted in WNW-ESE grabens consistent with the separation between Antarctica and Australia.
Southern Ocean biogenic blooms freezing-in Oligocene colder climates
2022, Nature CommunicationsSedimentary processes and facies on a high-latitude passive continental margin, Wilkes Land, East Antarctica
2019, Geological Society Special PublicationSubmarine glacial landforms on the cold East Antarctic margin
2016, Geological Society Memoir