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Location map showing the part of the Transantarctic Mountains and Ross Sea covered by this "Geology of southern Victoria Land" 1:250 000 map.
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The "Geology of southern Victoria Land" is a 1:250 000 map and monograph describing the geology of the largest ice-free area in Antarctica. Covering the region between the Fry Glacier in the north and the Skelton Glacier in the south (∼76°30'S-78°45'S), and from the Polar Plateau to Ross Island (158°E-170°E), the map replaces a 1:250 000 map publis...
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... Year of 1957-1958, with detailed work by earth scientists from New Zealand, the United States of America, Italy, Australia, and Russia in the following decades. This new geological map and monograph, covering the area from the Convoy Range to the Skelton Glacier (76°30'S to 78°45'S) and from the Polar Plateau to Ross Island (158°00'E to 170°00'E; Fig. 1), incorporates fieldwork undertaken as part of the International Polar Year 2007Year -2008 celebrations. It commemorates the achievements of the geologists of the "heroic era" (1901)(1902)(1903)(1904)(1905)(1906)(1907)(1908)(1909)(1910)(1911)(1912)(1913)(1914)(1915)(1916)(1917), and marks 50 years of earth science research in southern ...
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... geological map of the Ross Island and Dry Valleys region of Antarctica ( Fig. 1) has been completed as the final component of the QMAP (Quarter-million MAP) series of New Zealand's Institute of Geological and Nuclear Sciences (GNS Science). Within the period 1994-2011, QMAP built a geographic information systems (GIS) database of New Zealand geology and published 21 full colour 1:250 000 geological maps which ...
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... three major domains: the stable craton of East Antarctica; the Transantarctic Mountains; and the tectonically more active amalgamation of younger blocks which forms West Antarctica and the associated West Antarctic Rift System (Talarico & Kleinschmidt 2009). The Transantarctic Mountains extend across the continent for a distance of about 3800 km (Fig. 1), separating East and West Antarctica, and form a partial barrier to the thick continental ice sheet on East Antarctica. Mt Lister, at 4025 m, is the highest peak in the map area (Figs 4, ...
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... across ductile shear zones ( Figs 10, 11;Cook & Craw 2001;. This undermines the original basis for subdivision of the metasedimentary rocks into two groups and, following Cook & Craw (2001) and Wysoczanski & Allibone (2004), use of the term Koettlitz Group is abandoned; the basement rocks are here all included in an expanded Skelton Group (Fig. ...
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... at metre to decimetre scale within individual outcrops. Sedimentary structures and stratigraphy have for the most part been destroyed by deformation, and only a general indication of original lithologies is possible. Where possible, the map subdivides Skelton Group into informal lithologic units in which one particular rock type is predominant (Fig. 10). Given the lack of stratigraphic continuity and the obscuring effects of metamorphism and deformation, informal units were deemed to be more appropriate than using formations (e.g. Blank et al. 1963;Findlay et al. 1984). A number of marked changes within the Skelton Group occur near the Walcott Glacier, where the Frio Shear Zone has ...
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... is only exposed near McConchie Ridge (162°49.98'E 78°08.69'S), where it is a subtle kilometre- wide zone of elevated strain (Beckett 2002) that locally separates rocks with distinct metamorphic histories. On the basis of new structural data, this map extends the Frio Shear Zone across Chancellor Ridge and eastwards beneath the Howchin Glacier (Fig. 11). Although its nature and location are not particularly well constrained, the shear zone serves as a useful reference for distinguishing different structural domains within the Skelton Group (e.g. Wysoczanski & Allibone 2004) and potentially also marks some significant changes in age and composition of granitoids (see ...
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... with pebbly conglomeratic horizons containing quartz and quartzofeldspathic clasts in a matrix of diopside and actinolite. There are also pelitic metasediments nearby that include andalusite semischist, and garnet-biotite and kyanite-staurolite-garnet schists (mapped as schist; ss). The Pipecleaner Shear Zone, exposed at 162°39.68'E 78°14.45'S ( Fig. 11), but not labelled on the map, separates the above rocks (Radian sub-block, Cook & Craw 2001) from an area dominated by white, coarsely crystalline, deformed marble (sm) (Rücker sub-block). A kilometre- scale discontinuous layer of biotite-garnet schist (ss) could be either an original lithologic variant, or tectonically emplaced (Cook ...
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... and quartzofeldspathic schist with metabasite at the Cocks Glacier (undifferentiated; ss) were named Cocks Formation by Skinner (1982), although this name was not used by Cook (1997) or Cook & Craw (2002 The regional variation in Skelton Group metamorphic grade is illustrated in Figure 11. North of the Frio Shear Zone, the metamorphic grade is entirely upper amphibolite facies, with significant migmatisation (Allibone & Norris 1992). ...
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... pluton-and suite- based subdivision is followed here and the rocks are included in the Granite Harbour Intrusive Complex. Many, but not all, of these intrusives in the mapped area can be assigned to one of four petrogenetic suites ( Fig.14): ...
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... outcrops of heterogeneous mafic plutonic rocks adjacent to the upper Skelton Glacier, described by Read (2010) as the Skelton Mafic Suite, are here renamed the Skelton Mafic Intrusives (gam; Fig. 15). This unit includes the Delta Diorite (named from Delta Bluff on the Skelton Glacier by Gunn & Warren (1962), but the name is now abandoned), but other mafic bodies they mapped as Delta Diorite further north are not included (see below). Gabbroic rocks between the Foster Glacier and Mt Cocks adjacent to the upper Koettlitz Glacier ...
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... Granitoids (gaa), re-named from the Hillary Suite of Read (2001,2010), are granitoid intrusions extending from the Radian Glacier south to the Mulock Glacier. These are included in the Koettlitz Glacier Alkaline Suite on the basis of A-type chemistry and age (551-542 Ma; Fig. 15). They are mainly high silica alkaline granites with subordinate syenite, and form small intrusions adjacent to the Cocks and Foster glaciers, and between the Panorama and Kempe glaciers. Typically these granitoids are coarse- grained, comprising K-feldspar, quartz, plagioclase, and foliation-defining biotite which may be chloritised, ...
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... Bonney Pluton (grb; Smillie 1992) is the largest DV1a pluton, mapped from the northern face of the Olympus Range south to the Blue Glacier ( Fig. 16; Cox 1993). With a length of over 100 km and an area of more than 1000 km 2 , the pluton accounts for 15% of basement rocks exposed in the map area. Bonney Pluton typifies DV1a lithologies, ranging in composition from granodiorite through quartz monzodiorite to monzodiorite . Rocks commonly have well developed flow- aligned alkali ...
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... have well developed flow- aligned alkali feldspar megacrysts, mafic enclaves and hornblende in a matrix of plagioclase, alkali feldspar, biotite and quartz with accessory clinopyroxene, allanite, zircon, apatite, monazite, titanite and opaque minerals (Cox 1993). Locally there are megacryst swarms and zones with distinctive orbicular texture ( Fig. 16; Palmer et al. 1967;Dahl & Palmer 1981;Smillie 1989;). The margins of the pluton are commonly highly strained by post-crystallisation ductile-plastic flow ( Fig. 16; Cox 1993). Marginal zones are also choked with rafts and xenoliths of the host Skelton Group and older orthogneisses (e.g. Cox 1989Cox , 1993Smillie 1989). High- precision ...
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... clinopyroxene, allanite, zircon, apatite, monazite, titanite and opaque minerals (Cox 1993). Locally there are megacryst swarms and zones with distinctive orbicular texture ( Fig. 16; Palmer et al. 1967;Dahl & Palmer 1981;Smillie 1989;). The margins of the pluton are commonly highly strained by post-crystallisation ductile-plastic flow ( Fig. 16; Cox 1993). Marginal zones are also choked with rafts and xenoliths of the host Skelton Group and older orthogneisses (e.g. Cox 1989Cox , 1993Smillie 1989). High- precision U-Pb ages of 510.78 ± 0.56 Ma for the deformed marginal zone and 503.77 ± 0.37 Ma in the flow-foliated centre of the pluton have recently been obtained by CA- ...
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... and is compositionally a granite (Jones 1995a, 1997a). DV1a plutons typically contain mafic microgranite enclaves, elongated parallel to foliation, and interpreted as immiscible melt blebs (Smillie 1989;). Xenoliths of Skelton Group metasediments are typically crowded along pluton margins, where megacrysts are commonly deformed into augen ( Fig. 16), and together with schlieren and mafic banding may be deformed to give a swirly or chaotic appearance. The Catspaw Pluton (grc) is an elongate body of coarse- grained granite that extends from the Kukri Hills across the Taylor Glacier into the Asgard Range ( ). The Catspaw Pluton differs from megacrystic DV1a plutons in being ...
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... Skelton Group metasediments. Randomly oriented stocks and dikes of orthogneiss cut blocks of metasediment entrained within the pluton, especially on the margins (Jones 1997a). Chancellor Orthogneiss is strongly deformed, with a matrix of recrystallised quartz, biotite and feldspar wrapped around relict feldspars, which are commonly megacrystic ( Fig. 17). Accessory minerals are titanite, apatite and garnet. Chancellor Orthogneiss has not been dated and the limited geochemical analyses are of samples that are silica-rich and strongly evolved (Jones ...
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... bodies of biotite orthogneiss (gub), some containing garnet, are intercalated with Skelton Group rocks in many areas, including the Garwood Valley ( Blank et al. 1963; Portal Augen Gneiss of Mortimer 1981), the St Johns Range ( Turnbull et al. 1994) and the Wilson Piedmont region ( ; only the largest can be differentiated at 1:250 000 scale (Fig. 18). Few chemical analyses are available for these rocks so inclusion in the DV1b Suite is tentative. Numerous small undeformed biotite granitoid plugs and dikes (gf), tentatively assigned to the DV1b Suite, are widespread and also form larger and more obviously discordant ...
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... Coleman Pluton (gfc) is mapped only around Mt Coleman, northwest of New Harbour ( , where it intrudes Skelton Group metasediments and associated orthogneisses. The pluton is characterised by magmatic flow foliation, outlined by biotite-rich schlieren ( Fig. 17). Compositionally it is a monzogranite, with alkali and plagioclase feldspar, up to 30% quartz, minor biotite and distinctive accessory garnet. In some areas the pluton is almost completely replaced by younger Vanda ...
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... Pearse (ggp), Nibelungen (ggn), and South Fork (ggx) plutons underlie the western Asgard Range, from the Friis Hills above the western Taylor Valley, through the Nibelungen Valley to east of the Labyrinth in the upper Wright Valley (Fig. 19). They include granitic, monzonitic and quartz monzonitic rocks, often with considerable textural variation within individual plutons. Margins of these plutons are finer grained, and may be choked with enclaves to form intrusion breccias (e.g. Isaac et al. 1996). Mineralogically they comprise varying amounts of alkali feldspar ...
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... & Allibone in Turnbull et al. 1994) but this is atypical. Dike emplacement was more or less coeval with intrusion of DV2 plutons, and they commonly show mutually cross-cutting relationships, but the youngest dikes cut all other bodies. Enclaves lithologically equivalent to Vanda Dikes are common within some DV2 plutons (Allibone et al. 1993a; Fig. 19). The dikes typically dip steeply and the predominant strike is northeast-southwest; apart from minor brittle faulting they are undeformed. Individual dikes may be up to four metres wide and several kilometres long. Chilled margins are common. Both felsic and mafic varieties are normally porphyritic; felsic dikes usually cut mafic ...
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... Harbour Intrusive Complex is now unconformably overlain by near-horizontal, sandstone-dominated covering strata; the contact is well exposed at many localities in the eastern Dry Valleys, though commonly complicated by the presence of a thick sill of younger dolerite (Fig. 21). This unconformity is known as the Kukri Erosion Surface ( McKelvey et al. 1977; the Kukri Peneplain of Gunn & Warren 1962). It cuts across Late Cambrian -Early Ordovician granitoids and the sandstones above it are probably Early Devonian, hence it represents about 80 to 100 million years of ...
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... relatively small, cross-cutting dolerite plugs have been sources for sills in adjacent strata (Elliot & Fleming 2008). In places, sills thin and change orientation to become dikes; dolerite dikes are commonly seen cutting Beacon Supergroup strata (Fig. 31), and more rarely, cutting rocks of the Granite Harbour Intrusive Complex. Skew Peak is named from a thick Ferrar Dolerite dike or tilted sill which, near the summit, dips east at up to 30°. At Terra Cotta Mountain the Peneplain Sill is truncated and displaced by a dike 200-800 m wide; a swarm of thinner, more regular dikes intrudes ...
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... near the summit, dips east at up to 30°. At Terra Cotta Mountain the Peneplain Sill is truncated and displaced by a dike 200-800 m wide; a swarm of thinner, more regular dikes intrudes Beacon Supergroup strata of the north face but apparently not the large cross-cutting dike to the west, which may therefore be younger (Morrison & Reay 1995; Fig. 31). Typically, Ferrar dikes are one to several metres thick and laterally persistent, in sub-perpendicular sets which trend NW and ENE (Wilson 1992). A NNW- trending dike near Mt Fleming can be traced for about 4 km, and on the north flank of the Olympus Range a dike extends for 10 ...
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... the lack of detailed investigations of glacial deposits in these areas. Older undifferentiated local glacier till (ml) has also been mapped in the Coombs Hills, Beacon Valley and Asgard Range, principally according to its degree of modification and weathering, and proximity to glaciers and other nearby tills. The floor of the upper Beacon Valley (Fig. 41) is covered by a locally derived, dolerite- rich till, with irregular relief suggesting that it is ice-cored ( Linkletter et al. 1973), by possibly some of the oldest ice on earth ( Sugden et al. 1995b;Schaefer et al. 2000;Ng et al. 2005;Kowalewski et al. 2012). The Alpine 3 and 4 tills ( Hall et al. 1993), which were deposited by Late ...
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... deposits are interpreted to have formed from interlocked glacial-and-lake-ice systems that acted as conveyor belts to transport both fine and coarse sediment from glacial lobes westward into the ice-free valleys on rafts of lake ice (Clayton-Greene et al. 1988;Hall et al. 2001). Processes presently occurring at Trough Lake are a modern analogue ( Fig. 51; Hendy et al. 2000). Fine-grained lacustrine facies are for the most part poorly exposed and/or preserved, hidden beneath coarser lacustrine drift or beneath surfaces armoured by cobble and boulder ...
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... et al 1989;Pocknall et al. 1994;Turnbull et al 1994;Isaac et al 1996). Older colluvium (mc) occurs in ice-free valleys of the Quartermain Mountains, western Asgard Range, and Coombs Hills (Marchant et al.1993a,b). It includes the Koenig and Monastery colluvium units of Marchant et al. (1993a,b). ...
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... from the earlier phase are exposed in only three areas at the periphery of the volcano; elsewhere they are mantled by the younger eruptives, snow, and ice. Phase I eruptions were mainly subaerial but include rare pillow lava, diamictite and intrusive dike complexes, which were mainly trachytic in composition, with minor rhyolite and basanite (Fig. 61). The overlying Phase II rocks are subaerial basanitic lava flows, cinder cones and other pyroclastic deposits of picrobasalt, basalt, basanite, tephrite and trachybasalt, with lesser phonolite ( Fig. 62; Martin et al. 2010). K-Ar and Ar- Ar ages (Martin et al. 2010 and references therein) from Phase I rocks are in the range 18.7-11.4 ...
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... of intrusive relationships, lithology or outcrop characteristics. Name: from the Dry Valleys region of South Victoria Land. Type area: n/a Description: undeformed alkali-calcic monzonite, quartz monzonite, and granite plutons, enriched in K, Rb, Zr, and light Rare Earth elements and depleted in Na and Ca (not shown separately on map face, but see Fig. 14). Age: Cambrian-?Ordovician. late DV2 granitoids (gg, gg?; gg) Previous usage or definition: n/a Name: n/a Type area: n/a Description: late-stage granitoids, typically unfoliated homogeneous and massive with pegmatites and enclaves; postdate Vanda Dikes. Alkali-calcic ...
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... by Smillie (1992), modified by Allibone et al. (1993b). Name: from the Dry Valleys region of South Victoria Land. Type area: n/a Description: variably deformed calc-alkalic biotite quartz monzodiorite, granodiorite, and granite plutons with distinctive Sr, Na, and Al enrichment and Y and Nb depletion (not shown separately on map face, but see Fig. 14). Age: ...
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... by Smillie (1992), modified by Allibone et al. (1993b). Name: from the Dry Valleys region of South Victoria Land. Type area: n/a Description: variably deformed calc-alkalic quartz monzodiorite and granodiorite plutons similar to I-type Cordilleran-style, igneous rocks of convergent-margin settings (not shown separately on map face, but see Fig. 14). Age: Cambrian. undifferentiated DV1a granitoids (gro, gro?; gro) Previous usage or definition: n/a; includes granitoid referred to as Moraine Bluff Suite by Read (2010). Name: n/a Type area: n/a Description: medium-grained hornblende biotite granodiorite, monzodiorite and diorite; contains mafic enclaves and calc-silicate xenoliths. ...
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In this paper, we present detailed field observations, chronological, geochemical and Sr–Nd isotopic data and discuss the petrogenetic aspects of two types of mafic dykes, of alkaline to subalkaline nature. The alkaline mafic dykes exhibit a cumulate to foliated texture and strike NW–SE, parallel to the main trend of the region. The 40Ar/39Ar amphi...
Citations
... The former comprises a variety of lithologies from hornblende-biotite tonalite and granodiorite to granite, leucogranite, and syenite. They show meta-luminous I-type to peraluminous S-type and high-K calc-alkaline to shoshonitic affinities [17,18,31,[47][48][49]. Zircon U-Pb dating shows that they were emplaced over a long period from~580 Ma to 470 Ma, with the main magmatic pulse between~530 Ma and 480 Ma [11,12,18,27,28,[50][51][52][53][54]. ...
... The transition from calc-alkaline to alkaline magmatism is indicative of a geodynamic switch from compressive to extensional regimes [75][76][77][78]. In the Victoria Land, the Larsen granodiorite, which extends south of the Fry glacier, has calc-alkaline affinities, similar to the~505 Ma Bonney pluton (a portion of the GHI in southern Victoria Land) comprising foliated diorite, monzodiorite, and granodiorite [49,79]. Although the Larsen granodiorite in the Central Victoria Land remains poorly studied, it probably has similar geochemical features. ...
It has been accepted that granitoids of the Irizar unit in the Central Victoria Land (Antarctica), as an important part of the Granite Harbour Intrusives, were formed in a post-collisional setting during the Ross orogeny along the margin of east Gondwana. However, the emplacement ages of the Irizar unit remain poorly constrained, making it difficult to form a more complete picture of the geodynamic evolution of the Ross orogen and its counterpart (Delamerian orogen) in southeast Australia. In this work, four syenogranite samples from the Irizar unit were chosen for SHRIMP zircon U-Pb dating, which yielded ages of 507.8–489.7 Ma. The new geochronological data indicate that the post-collisional extension in the Central Victoria Land had begun by ~508 Ma, much earlier than previously thought (i.e., 490–480 Ma). Integrated with U-Pb ages for Early Paleozoic granitoids from the literature, the Ross–Delamerian orogen shows that the post-collisional granitic magmatism initiated at ~515 Ma in the Central Transantarctic Mountains and northward systematically decreased to ~508 Ma in the Victoria Land, and then to ~487 Ma in southeast Australia. This can be explained well by the propagating northward transition from pre- and syn-collisional compression to post-collisional extension.
... The Beacon Supergroup strata unconformably overlie an important erosional surface (Kukri Erosion Surface) onto the crystalline basement referred to the latest Proterozoic-early Paleozoic Ross Orogen (Barrett, 1991;Stump, 1995;Cox et al., 2012;Elliot, 2013). The basement is mainly made up of igneous rocks of the Granite Harbour Intrusive Complex, and high-to very low-grade metamorphic rocks (Stump, 1995;Cox et al., 2012;Goodge, 2020). ...
... The Beacon Supergroup strata unconformably overlie an important erosional surface (Kukri Erosion Surface) onto the crystalline basement referred to the latest Proterozoic-early Paleozoic Ross Orogen (Barrett, 1991;Stump, 1995;Cox et al., 2012;Elliot, 2013). The basement is mainly made up of igneous rocks of the Granite Harbour Intrusive Complex, and high-to very low-grade metamorphic rocks (Stump, 1995;Cox et al., 2012;Goodge, 2020). The Beacon Supergroup mainly consists of terrestrial siliciclastic sediments, mostly sandstone, mudstone, and minor conglomerate, deposited in an alluvial environment, with minor depositional intervals recording glacial and shallow-marine paleoenvironments (Barrett and Kohn, 1975;Barrett, 1991;Isbell and Cúneo, 1996;Gulbranson et al., 2020). ...
... The Taylor Group in SVL is up 1400 m thick, subdivided into eight lithostratigraphic formations (Cox et al., 2012) while the Victoria Group, disconformably overlying it, is subdivided into six formations (Cox et al., 2012). In the whole, the Victoria Group reaches a maximum thickness of ca. ...
Between Permian to Triassic, the Earth experienced climatic and biotic crises, included the
greatest mass extinction at the Permian-Triassic boundary. These climatic and biological changes are
reflected in both marine and terrestrial depositional systems. Over this time span, the Gondwana
supercontinent hosted numerous large basins that may preserve the paleoenvironment response to
global changes in the sedimentary record. This study provides a lithostratigraphic reappraisal of the
latest Paleozoic-Mesozoic alluvial Beacon Supergroup at Allan Hills (Convoy Range), which is one of
the most complete sedimentary sequences in Antarctica. Fieldwork stratigraphic-lithological
observation, facies analysis, and petrographic characterization of sedimentary rocks allow the
identification of six depositional units. The investigations point out for a conformable relationship between depositional and lithostratigraphic units, characterized by changes in the fluvial style. The reconnaissance of a “transitional interval” showing intermediate features between the Permian Weller
Coal Measures and the Triassic Feather Conglomerate strengthen the conformable nature of the sequence across the Permian-Triassic boundary in this region. The lithological features of such
interval strongly resemble those observed in the coeval deeply studied Eastern Australia successions
crossing the Permian-Triassic boundary as well as the end-Permian extinction. More precisely, the
uppermost coal occurrence, just above a glossopterid macroflora-bearing carbonaceous mudstone
within the “transitional interval”, marks the disappearance of coal-peat forming Permian vegetation
which corresponds with the terrestrial end-Permian extinction, thus representing one of the few end-
Permian extinction records in Antarctica.
... northern Victoria Land; SVL = southern Victoria Land; CTAM = Central Transantarctic Mountains; QMM = Queen Maud Mountains. Simplified and exaggerated distributions of the Granite Harbour Intrusives of the Ross Arc are taken from the following papers: in northern Victoria Land (NVL), Läufer et al. (2011); in southern Victoria Land (SVL), Wysoczanski and Allibone (2004) and , with DV=Dry Valleys area; KG = Koettlitz Alkaline Province BG = Byrd Glacier area (from Cox et al., 2012, and; in the Central Transantarctic Mountains (CTAM), Goodge et al. (2004bGoodge et al. ( , 2020, with MR = Miller Range; in the Queen Maud Mountains (QMM, including the Horlick Mountains), Stump (1995) and Paulsen et al. (2015Paulsen et al. ( , 2020. W.Tas = West Tasmania Terrane. ...
New insights into the Late Precambrian-latest Devonian evolution of the Pacific margin of Gondwana are obtained by treating the margin in terms of three key tectonic elements: i) the in situ part of the Ross Orogen of Eastern Antarctica (Wilson Terrane) built on, and fringing, older crust; ii) the largely in situ southern Tasmanides of eastern Australia; and iii) offshore basement and island arc terranes now accreted either to the Ross Orogen, the Tuhua Orogen of southwestern New Zealand or, in one case, to the Australian Tasmanides. Detailed correlations between these elements suggest that the onset of convergence was essentially simultaneous along the margin over an original distance of ~1000 km. The first appearance of subduction-related igneous rocks occurred at ~540–530 Ma in the Tasmanides; ~535–530 Ma in the Tiger Arc of northern Victoria Land; and 550 Ma in southern Victoria Land of the Ross Orogen.
New correlations of this paper suggest possible but unconstrained trajectories of offshore terranes. The Bowers Terrane was accreted to the East Gondwana margin at ~491 Ma, producing the main Ross Orogeny. The adjoining Takaka Terrane had docked briefly with that margin at ~497–494 Ma (Haupiri Disturbance in New Zealand) before crustal extension rifted it oceanward to drift away in the latest Cambrian to become subsequently amalgamated with the sedimentary Buller Terrane at ~390 Ma. The West Tasmania Terrane was accreted to the East Gondwana margin beginning at~500–499 Ma (generating phase 3 of the Tyennan Orogeny) and the connected Selwyn Block to the Tasmanides at ~500 Ma (main Delamerian Orogeny).
Our new interpretations suggest that previous lithological correlations of subduction-related volcanics between the Ross Orogen and southern Tasmanides did not take into account major rollback in the Tasmanides from ~514 to ~503 Ma. Similarly, they suggest that the ~550–480 Ma Granite Harbour Intrusive roots of the continental margin Ross Arc are not correlatives of 514, 505 and ~ 495–470 Ma granites intruding the Kanmantoo Group in the Delamerian Orogen of South Australia, either in time or in tectonic setting. We also recognize an early (~520–516 Ma) boninitic infant arc event in the outboard West Tasmania, Bowers, and Takaka terranes that predated ~500 Ma more mature arcs in the last two. Arc-related magmatism in the Ross Orogen reflects the interplay between two main subduction systems — that which generated the Ross Arc and an outboard one that generated intraoceanic arcs.
Three major turbidite fan systems developed along the East Gondwana margin as responses to major deformations. Early Cambrian fan system 1 postdates the Beardmore Orogeny and includes the Kanmantoo Group in the Delamerian Orogen and the Berg and upper Priestley formations in the Wilson Terrane. Cambrian-Ordovician fan system 2 (the Robertson Bay Group, the Swanson Group in Marie Byrd Land, the Greenland Group in the Buller Terrane and the St Arnaud Group in the Delamerian Orogen) and Lower-Middle Ordovician fan system 3 (turbidites of the Eastern Lachlan Orogen, the Buller Terrane (New Zealand) and East Tasmania Terrane) both postdate different parts of the Ross Orogeny. Cessation of fan system at ~458 Ma correlates with ‘accretion’ of the Robertson Bay Terrane in northern Victoria Land.
... Much of the southern coastal zone of the ASMA is characterised by the Ross Sea 1 Drift deposits intersected by glaciers. The Ross Sea 1 Drift forms an almost continuous band from the Wright and Taylor valleys to the southern end of the Dry Valleys ASMA and is commonly ice cored and characterised by an abundance of kettles and eskers with frequent accumulations of mirabilite from evaporites from previous water bodies (Cox et al. 2012;Perotti et al. 2018). Inland of the Ross Sea 1 Drift is a complex geological setting of basement granites overlain by ancient sedimentary deposits much of which remained ice free through recent glaciations. ...
... The dense cluster of small ponds in the SE corner of Fig. 3 coincides with the distribution of the Ross Sea Drift 1 (Cox et al. 2012;Perotti et al. 2018). The second group of small ponds in the northern part of the MDV ASMA is situated on an extensive area of glacial moraine close to 77°S in the Alatna Valley-McKay Glacier area (Fig. 3). ...
... The second group of small ponds in the northern part of the MDV ASMA is situated on an extensive area of glacial moraine close to 77°S in the Alatna Valley-McKay Glacier area (Fig. 3). Water bodies on glacially derived, thermokast formations such as the Ross Sea 1 Drift are known as kettles or kettle holes (Cox et al. 2012). Because these ponds were a distinct subset by virtue of their high density, small size and occupation of recent glacial terrain, we separated these as the first dichotomy in our classification. ...
The McMurdo Dry Valleys are the largest single ice-free area in Antarctica, and of considerable scientific and conservation value as an extreme polar desert. This is recognised through the McMurdo Dry Valleys Antarctic Specially Managed Area (ASMA), where management's goals focus on protection of its unique features, while facilitating science access. Using a mix of remote sensing and existing cartography, we have identified over 6000 lakes and ponds in the ASMA. This study develops a classification of those aquatic ecosystems to provide a framework for management. It uses a limited top-down, hierarchical classification to define 13 class separations based on physical attributes that could largely be ascribed from existing databases or remotely sensed information. The first hierarchical level was based on landscape position, separating coastal kettle holes (reflecting recent glacial history), from other "topographic" water bodies. The second level was based on endorheic vs exorheic drainage, the third on mid-summer ice condition (no-ice cap; ice capped; frozen to base) and the fourth on source of inflow (glacial or non-glacial). Kettles were sub-classed by mid-summer ice only. Classes were tested against a set of field observations and an expert workshop validation process considered management implications for the ASMA. This study shows how the classification assists our understanding of Dry Valley landscapes and addresses management issues faced by researchers, environmental managers and policy makers. The approach to classification, rather than the detailed classes that may be specific to the Dry Valleys, has potential for wider use in other polar landscapes.
... The Ross Orogen plutonism is known collectively as the Granite Harbour Intrusive Complex (Cox et al. 2012; Figure 1) and rocks thought to be equivalent to this have been mapped in New Zealand (Gibson and Ireland 1996;Allibone et al. 2009a). At least four examples of Cambrian plutonism in New Zealand are thought to equate to Ross Orogen-related rocks. ...
Antarctica and Zealandia were once-adjacent blocks of Gondwana with a shared magmatic history during the Mesozoic and earlier. This is preserved in (a) shared Palaeozoic and Mesozoic Gondwana plutonism; (b) magmatism associated with syn-Gondwana breakup, including Jurassic-aged dolerite rocks of the Ferrar large igneous province, and igneous intrusions of similar isotopic affinity occurring on both continents coeval with Late Cretaceous rifting of Antarctica from Zealandia. The shared magmatic history continued post-Gondwana breakup through (c) the generation of oceanic crust and (d) eruption of diffuse alkaline magmatic province (DAMP) rocks. The DAMP encompasses magmatism from the Late Cretaceous to present day that shares isotopic and trace element characteristics over a (now) widely dispersed area of the southwest Pacific. This has been ascribed to either a previously contiguous mantle lithosphere with a shared, syn-Gondwana breakup history contributing to volcanic melts or to an isotopically distinct Antarctica – Zealandia asthenospheric mantle domain. The development of the Antarctic ice sheet after 34 Ma resulted in many volcanoes recording ice interactions that reveal many new details of Antarctica’s palaeoenvironmental history. Study of the volcanic history of Antarctica helps to advance understanding of the geological history of the region, including once-conjugate continents like Zealandia.
... S3found at http://dx.doi.org/10. 1017/S0954102019000129). Palaeozoic granitoids are widespread in the Wright Valley and the probable source of these contaminants is old feldspars(Cox et al. 2012). ...
Reliably dated surficial deposits for reconstructing palaeoclimate are rare in the McMurdo Dry Valleys of Antarctica. While many tephra have been found and dated, none is well characterized. In the Wright Valley, the Hart Ash is poorly dated and described. This paper reports profiles through tephra, the chemical signature of the glass shards and new high-precision multi-crystal laser fusion of ⁴⁰ Ar/ ³⁹ Ar ages. Major and trace element analyses of glass shards indicate the tephra are phonolitic and most probably sourced from Mount Discovery in the Erebus volcanic province. Two chemically distinct and stratigraphically separate tephra layers within the Hart Ash were found in three closely spaced soil profiles. The complex stratigraphy between these profiles could not be delineated without the geochemistry of the tephra. Importantly, our data suggest that only one tephra may be an in situ fall-out deposit, which gave a robust age of 2.97 ± 0.02 Ma. This new age for the Hart Ash tephra, which is 10 cm thick and is preserved at the current surface, provides a maximum age for surface deposits in the lower Wright Valley. This study highlights that well-characterized tephra enhance stratigraphic correlations in the Dry Valleys and improve the accuracy of palaeoenvironmental interpretations.
... Major rifting in the VLB has occurred since the latest Eocene ( , and the basin now contains more than 14 km of Mesozoic and Cenozoic sediments and volcanic detritus. Paleozoic and Mesozoic units in the Transantarctic Mountains and local volcanoes of the late Cenozoic McMurdo Volcanic Group (McMVG;Kyle, 1990;Wilch et al., 1993) are the main sources of sediments deposited in the VLB (e.g., Cox et al., 2012). ...
During the 2007 ANtarctic geological DRILLing (ANDRILL) campaign in the Ross Sea, Antarctica, the AND‐2A core was recovered through a stratigraphic succession spanning 1,138.54 m of Neogene sedimentary rocks that include an expanded early to middle Miocene sequence. The study reported here focuses on the magnetic properties of the interval from 778.63 m below sea floor (mbsf) to 1,138.54 mbsf, which comprises a time interval spanning 1.5 Myr, from ~18.7 to ~20.2 Ma. We recognize three main pulses of increased input of magnetic materials to the drill site between 778.34–903.06, 950.55–995.78, and 1,040–1,103.96 mbsf. Trends in the magnetic mineral concentration dependent parameters mirror changes in the proportion of sediments derived from McMurdo Volcanic Group rocks. We suggest that these pulses in magnetic mineral concentration reflect changes in sediment transport processes associated with changing glacial conditions at the drill site that included (1) subglacial and grounding zone proximal settings, (2) hemipelagic and neritic conditions with abundant sediment‐rich icebergs, and (3) grounding zone‐distal environment that was covered by land‐fast multiyear sea ice or a fringing ice shelf. The magnetic minerals record preserved in the AND‐2A core supports other data that indicate a highly dynamic and variable coastal environment during the early Miocene, where glaciers retreated inland under warm climatic conditions and advanced beyond the drill site across the continental shelf when cold climate prevailed.
... Deposition in this environment may be more favourable to larger magnetic grains, with the finer mud fraction being winnowed during periods of higher bottom water currents. Examination of the coarse fraction in these cores indicates the presence of McMurdo Volcanic Group, which dominates the McMurdo Sound Region (Cox et al., 2012). RS15-LC48 and RS15-LC108 lie further offshore on the lower continental rise and abyssal plain, in a lower energy environment that is bathed in AABW. ...
The Ross Sea is one of the major sites of formation for Antarctic Bottom Water (AABW), a key component of the global ocean overturning circulation. However, there is currently a lack of high quality stratigraphic records documenting how this water mass flows from the continental shelf into the abyssal ocean, and specifically how this pathway is affected by changes in ice sheet cover on the Ross Sea continental shelf through Pleistocene glacial-interglacial cycles. Over the course of two expeditions in 2015 and 2016, a suite of cores from the upper continental slope to the abyssal plain was obtained by the Korea Polar Research Institute from the R/V Araon. The age of these cores ranges from Holocene to the latest Pliocene, and they hold the potential to document a source-to-sink record of AABW transfer into the abyssal Pacific Ocean. The cores are located in regions with distinct differences in bottom water energy, with high-energy cascading water masses on the upper slope creating the potential for erosional hiatuses, passing downslope into a lower energy setting. To decipher the complex environmental records and allow core-to-core correlation, robust chronostratigraphies are essential. Here, we present age models for four of these cores, based on correlation between their magnetostratigraphy and the geomagnetic polarity timescale, resulting in sedimentation rates between 1.5 cm/ky and 0.5 cm/ky. Rock magnetic data indicate the remanence is carried by magnetite with an almost ubiquitous contribution of high coercivity fraction that is not demagnetised by 100 mT. We demonstrate that a reliable magnetostratigraphy is established for each of these cores, and magnetic properties can be used to identify potential hiatuses in the cores and as a proxy for sedimentary grain-size.
... Along the TAM, the base of the Beacon Supergroup is diachronous, being older in southern VL and Central TAM (Devonian) and younger in northern Victoria Land (Permian to Triassic), with variable thickness between 1 and~2.5 km in central and southern VL and much less in northern VL (see Elliot and Fleming, 2004 and references therein). Despite of some regional variability, in our study area the base of the Beacon Supergroup is considered almost synchronous of Permian age (Cox et al., 2012). There, the deposits of the Beacon Supergroup attain about 2 km of thickness, showing undeformed sub horizontal bedding gently dipping westwards. ...
... The Royal Society Range encompasses an area between the Ferrar and Skelton glaciers (Fig. 2). Basement rock lithology is mainly represented by the Skelton Group, made up of marbles, schist and medium-grade metamorphic rocks, and by intrusive rocks of the Koettlitz Group (mafic intrusives), and subordinate Granite Harbour Intrusive rocks (Cox et al., 2012). The Beacon Supergroup is represented by the Devonian Taylor Group. ...
... We extracted the elevation of Kukri surface and basement top in different ways: i) after geo-referencing the geological map (1:250000 map scale of Gunn and Warren, 1962), to the Radarsat DEM; ii) for the Convoy Range, Dry Valleys, and Royal Society Range we used the 1:250000 scale geological maps recently edited by the Institute of Geological and Nuclear Science of New Zealand (Cox et al., 2012); iii) for the southern region we used the 1:1.000.000 geological maps of Craddock et al. (1969) and the paper of Foley et al. (2013). ...
The Transantarctic Mountains (TAM) are an imposing topographic feature, forming the western shoulder of the Meso-Cenozoic West Antarctic Rift System. Although the TAM topography is similar to other continental rifts, some aspects such as the high topography and the transition in the mode of crustal extension from orthogonal to oblique rifting during the Cenozoic makes the TAM an anomalous rift margin. Here, we present a topography analysis of a 600 km long transect along the TAM front in southern Victoria Land combined with a large available thermochronological data-set to decode the tectonic signals hidden in the topography. An along-strike variability in tectonic, erosional and geomorphic characteristics is detected. We then focus our analysis on the Royal Society Range, where structural investigations were integrated with new fission track thermochronology in order to assess the morphotectonic evolution of the region. Fission-track data and topography of the Royal Society Range reveal remarkable differences with respect to the neighboring areas. Topography characteristics and thermal modeling suggest an increase in tectonic activity during late Eocene-early Oligocene times and structural analysis suggests that the Cenozoic rifting has been controlled by dextral transtension, as proposed for others sector of the TAM front. The detected along-strike variability in tectonic, erosional and geomorphic characteristics may reflect geodynamic complexities that should be taken into account in any further model of the TAM evolution.
... In the McMurdo Sound, ice supplied by Skelton and Mulock Glaciers during the LGM flowed over the volcanic islands and peninsulas of the region and into the Dry Valleys (Stuiver et al., 1981;Denton and Hughes, 2000;Denton and Marchant, 2000;. The glacial deposits left by this ice sheet are known in the region as Ross Sea Drift (Stuiver et al., 1981;Cox et al., 2012) and they are the result of multiple advances and retreats of the ice sheet occurred during the Quaternary. Onshore reconstructions of the LGM grounded ice sheet in McMurdo Sound are based essentially on the extension of the most recent of these deposits, the Ross Sea 1 Drift (Cox et al., 2012). ...
... The glacial deposits left by this ice sheet are known in the region as Ross Sea Drift (Stuiver et al., 1981;Cox et al., 2012) and they are the result of multiple advances and retreats of the ice sheet occurred during the Quaternary. Onshore reconstructions of the LGM grounded ice sheet in McMurdo Sound are based essentially on the extension of the most recent of these deposits, the Ross Sea 1 Drift (Cox et al., 2012). The geomorphology, chronology and erratic distributions of these glacial sediments have been extensively investigated (Denton and Hughes, 2000;Denton and Marchant, 2000;Hall and Denton, 2005;Hall et al., 2013;Anderson et al., 2014). ...
... The western side of McMurdo Sound is topographically dominated by the South Victoria Land (SVL) sector of the Transantarctic Mountains. A late Proterozoic-Cambrian metamorphic basement is composed of upper-amphibolite to upper greenschist facies rocks of the Skelton Group, in the past referred as the Koettlitz Group (Findlay et al., 1984;Cook and Craw, 2001;Cox et al., 2012). In general, regional metamorphism of the Skelton Group is of low Pressure/high temperature conditions (Allibone, 1992). ...
The provenance of Ross Sea Drift deposits from the McMurdo Sound region (Antarctica), ranging from middle Quaternary to a Last Glacial Maximum (LGM) age, has been investigated by means of petrographic techniques. A total of 19 bulk till samples from four areas was analyzed for three different granulometric fractions: pebble to cobble, granule, and coarse to very coarse sand grain size. Deposits were classified following the lithological composition of clasts and occurrence of different petrographic groups was evaluated for each sample. Clasts composition predominantly reflects source rocks cropping out in the region between Mackay and Koettlitz glaciers, with McMurdo Volcanic Group rocks being the most represented lithologies in the Royal Society Range foothills, while Granite Harbour Intrusive Complex rocks are more widespread in Taylor and Wright valleys. The lithological distribution of collected samples supports a distal provenance related to a grounded Ross Ice Sheet in Taylor Valley, while the specific distribution of volcanic lithologies in Royal Society Range foothills is evidence for a northward ice flow from Koettlitz Glacier catchment, thus supporting previous glaciological models of an expanded lobe during the LGM. In addition, middle-Quaternary Trilogy Drift composition from Wright Valley accounts for a local provenance, thus allowing the hypothesis of a thickened Wilson Piedmont Glacier rather than a grounded Ross Ice Sheet during past ice advances.
