Terra Antartica 2004, 11(1), 55-65 © Terra Antartica Publication

Revision of the Terrane Model of Northern Victoria Land (Antarctica)

N.W. ROLAND1, A.L. LÄUFER2 & F. ROSSETTI3

1Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hannover - Germany 2Johann Wolfgang Goethe-Universität, Geologisch-Paläontologisches Institut, Senckenberganlage 32-34, 60054 Frankfurt a.M. - Germany 3Dipartimento di Scienze Geologiche, Università “Roma Tre”, Largo S.L. Murialdo 1, 00146 Roma - Italy

Received 30 April 2004; accepted in revised form 30 July 2004

Abstract - During the joint German-Italian Antarctic expedition 1999-2000, new tectonic results triggered a revisiting of the classic terrane model for northern Victoria Land which postulated three terranes, the high- grade Wilson Terrane and the very low-grade to low-grade Bowers and Robertson Bay terranes. The brittle character of the former terrane boundaries was studied in detail and it was shown, that Meso- to Cenozoic brittle to semi-brittle tectonics has overprinted the inherited Early Palaeozoic structural pattern to a large extent. In addition to a revision of the Ross-orogenetic pattern in northern Victoria Land, the tectonic history and the arguments for a simple three-terrane model were questioned. A new model is proposed, which accepts the allochthonous character of arc volcanics and sediments, now called the Bowers Arc Terrane. These Bowers Arc rocks collided due to W-directed subduction processes with the Wilson active margin of Gondwana. As it is not yet proven that the Wilson plutonic and metamorphic rocks form a distinct terrane themselves, the term Wilson Terrane is abandoned consequently in favour of the newly suggested Wilson Mobile Belt. In addition, there are no proofs that the metasedimentary rocks of the Robertson Bay Group metasedimentary rocks docked as a separate terrane to the Bowers Arc Terrane. These turbidites were deposited after docking of the Bowers Arc and represent the continued sedimentary history in an accretionary environment at the Gondwana active margin.

INTRODUCTION: THE TERRANE MODELS The Lanterman Fault forms the boundary between OF NORTHERN VICTORIA LAND the Wilson and the Bowers terranes, while the Leap Year Fault separates the Bowers Terrane from the Northern Victoria Land (NVL) is located at the Robertson Bay Terrane (Gair et al., 1969; Bradshaw boundary between East and West Antarctica, at the et al., 1985; Gibson, 1985; GANOVEX Team, 1987) Pacific termination of the Transantarctic Mountains (Fig. 1). (Fig. 1). The overall tectonic architecture of NVL has Such high-angle, NW-SE-striking fault systems been commonly referred to the assembly and show a complex and polyphased tectonic activity stabilisation of three different NNW-trending, from Early Palaeozoic to Cenozoic times (Capponi et Neoproterozoic to Early Palaeozoic, fault-bound al., 1999; Rossetti et al., 2002; 2003). In particular, lithotectonic units or “terranes” onto the East different models have been proposed for the Early Antarctic Craton during the Early Palaeozoic Ross Palaeozoic kinematics along these major fault orogeny (e.g. Bradshaw et al., 1985; GANOVEX systems: Team, 1987; Kleinschmidt & Tessensohn, 1987; Borg (1) high-angle normal faults bordering the “Bowers & Stump, 1987; Stump, 1995). These terranes are Graben” (Stump et al., 1983), from west to east: the Wilson, Bowers, and Robertson (2) major strike-slip faults (Weaver et al., 1984), Bay terranes. Weaver et al. (1984) introduced and (3) thrusts, at least at the Lanterman Fault , which Bradshaw et al. (1985) extended the concept of possibly originated as back-thrusts following the suspect terranes and Cambrian tectonics as a major collision of the Early Palaeozoic palaeo-Pacific contribution to the geological framework of NVL and active margin of Gondwana with a west-facing hence increased the number of possible terranes. In island arc (Gibson & Wright, 1985), and addition to the Wilson, Bowers, and Robertson Bay (4) boundaries between different terranes (e.g. Weaver terranes, they in fact outlined within the Wilson et al., 1984; Gibson, 1985; Bradshaw et al., 1985; Terrane a so-called Daniels Terrane and a Lanterman Kleinschmidt & Tessensohn, 1987). Terrane and separated a Millen Terrane from the Although the existence of these defined suspect Robertson Bay Terrane. terranes remained doubtful and was subject to

*Corresponding author ([email protected]) 56 N.W. Roland et al.

Fig. 1 – Tectonic sketch map of northern Victoria Land.

continuous debate, Palaeozoic accretion at the palaeo- THE CLASSIC “TERRANES” Pacific margin of Gondwana and the general distinction of three major terranes in NVL have been THE WILSON TERRANE widely accepted, and the Lanterman and Leap Year faults are commonly interpreted as the main suture The medium- to high-grade metamorphic Wilson zones of the Ross Orogen (e.g. Kleinschmidt & Terrane consists mainly of schists, gneisses, and Tessensohn, 1987; Kleinschmidt et al., 1987; migmatites, the latter often closely related to the late GANOVEX Team, 1987; Stump, 1995; Ricci et al., intrusions of the Granite Harbour Igneous Complex, 1997; Capponi et al., 1999) (Fig. 1). the majority of which gave ages between 520 and In this paper, we first review the geological setting 480 Ma (cf. Goodge, 2003 and references therein). In of NVL and then we provide a number of arguments contrast, U/Pb geochronology particularly in southern against the classic “terrane model” of NVL. These Victoria Land and in addition on clasts in NVL arguments are consistent with the new findings conglomerates suggests that granites older than 520 obtained during the joined German-Italian Antarctic Ma up to 550 Ma are widespread and in places Expedition 1999-2000 and provide a new scenario for predominant (e.g. Encarnación & Grunow, 1996; the reconstruction of the palaeo-Pacific active margin Bassett et al., 2002; Goodge, 2003 and references of Gondwana within a subduction-accretion related therein). Biotite-plagioclase-quartz-paragneisses tectonic setting. prevail, but local occurrences of sillimanite-garnet- Revision of the Terrane Model of Northern Victoria Land 57 cordierite-K-feldspar-green spinel assemblages are conglomerates, and rare limestones. Slope reported from the Terra Nova Formation and graphitic facies turbidites occur in the SW, shelf facies staurolite-garnet-mica schists as well as silicate in the NE. marble and graphite-bearing marble from the Dessent * Mariner Group (late Middle to early Late Formation (GANOVEX Team, 1987). In addition, Cambrian: shallow-marine, fossiliferous granulite facies rocks are reported from the mudstones, limestones, sandstones, and Matusevich Glacier (Oates Coast) and the Campbell occasionally thick conglomerates). Glacier area (NVL). Recent SHRIMP-data of detrital * Leap Year Group (late Upper Cambrian to ?Lower zircons support a model of high-grade and partly Ordovician: Cooper et al., 1976; Dow & Neall, granulite-facies metamorphism and igneous activity in 1974): Polymict, very coarse conglomerates at the the Oates Coast basement are confined to a relatively base, followed by white to reddish fluvial to short period between the late Cambrian and early deltaic quartzites and quartz pebble bearing Ordovician (Henjes-Kunst et al., 2003, this vol.). The conglomerates with subordinate red silty eastern boundary of the Wilson Terrane with the mudstones. The Leap Year Group rocks rest Bowers Terrane is located in the Lanterman Range unconformably on the Mariner and Sledgers and consists of a mafic-ultramafic highly-strained belt Groups and are best interpreted as molasse-type with remnants of ultrahigh pressure rocks, which is sediments. It can partly be subdivided in: Carryer indicative of subduction of palaeo-Pacific oceanic Conglomerate, Reilly Conglomerate, Camp Ridge crust (e.g. Capponi et al., 1997; Ricci et al., 1997; Quarzite (see GANOVEX Team, 1987, also for Talarico et al., 1998). Recently reported findings of further references). coesite in these rocks underline the early high- According to Bassett et al. (2002) the Cambrian pressure metamorphism along the boundary (Ghiribelli Bowers Terrane intra-oceanic volcanic arc accreted to et al., 2002). In addition to the medium- to high- the Gondwana continental margin prior to the grade metamorphic units, the Wilson Terrane contains deposition of the Carryer Conglomerate of the Leap several occurrences of low-grade rocks, such as the Year Group. Isotopic provenance analysis of granitoid Priestley Formation, Rennick Schists, Berg Group etc conglomerate clasts provides constraints on the age of (GANOVEX Team, 1987). The age relations of these the accretion, which is “bracketed by the 511 Ma rocks of different metamorphic grades are still a Sledgers clast age and the 504 Ma Carryer clast ages matter of debate. placing the event in the upper Middle Cambrian” (Note: this is a granitic clast in the Sledgers Group conglomerate, not a clast of Sledgers Group THE BOWERS TERRANE metasedimentary rocks).

The Bowers Supergroup is exposed in a 20-30 km wide belt bound by extensive fault zones with strike- THE ROBERTSON BAY TERRANE slip-dominated brittle kinematics. The Bowers Supergroup comprises a variety of volcanic and The external Robertson Bay Terrane represents a sedimentary rocks and is divided into the ?Early to roughly 200 km wide metasedimentary unit E of the Middle Cambrian Sledgers Group (e.g. Laird et al., Bowers Terrane. It consists of: 1982; Wolfart, 1994; Cooper et al., 1996; Bassett et - The Robertson Bay Group (Late Cambrian to al., 2002; Henjes-Kunst, 2003), the Middle to Late Early Ordovician) with very thick, folded Cambrian Mariner Group (Laird et al., 1982; successions of monotonous turbiditic greywackes Wodzicki & Robert, 1986) and the Late Cambrian to alternating with silty mudstones. No volcanic Earliest Ordovician Leap Year Group (e.g. Cooper et intercalations and no coarse conglomerates have al., 1967, 1982). All together, the Bowers Supergroup been found so far. The turbidites were deposited represents more than 6.5 km of sedimentary and in a distal fan to basal plains sedimentary volcanic rocks. environment with approximately NNW directed From old to young, these main lithostratigraphic transport ± parallel to the main strike of the units consist of the following subunits and lithologies: Robertson Bay lithotectonic unit (Wright, 1981; * Sledgers Group (from bottom to top): Field & Findlay, 1983; Wright et al., 1984). The - Solidarity Formation: submarine tholeiites detrital components in the greywackes are mainly - Glasgow Volcanics (Middle Cambrian and clasts of quartz and lithic fragments, which older): Mafic, mainly submarine lavas (pillow generally indicate a rather uniform mature lavas), volcanic breccias, tuffs and tuffites. The continental provenance consisting of medium- to tholeiitic and calc-alkaline basalts to rhyolites high-grade rocks (Wright, 1981). erupted in an intra-oceanic arc environment. - Handler Formation (Cambrian/Ordovician - Molar Formation (Middle Cambrian and older): boundary): Greywackes and slates as in the Alternating greywackes and mudstones with Robertson Bay Group, but in addition minor red minor intercalated siltstones, grits, slates, pebbly mudstones, and exotic blocks of 58 N.W. Roland et al.

fossiliferous limestones and sandstones, quartz- fragment of continental or oceanic material welded to pebble conglomerates, and quartz sandstones (cf. a cratonic area by accretion at an active continental GANOVEX Team, 1987). The blocks reach margin. In this sense, “terrane” was applied to diameters from a few cm up to 7 m. Fossils in describe the structural development of NVL the limestone blocks indicate a depositional age (Bradshaw et al., 1985). However, the term is from around the Cambrian/Ordovician boundary obviously changing its meaning at present, as the into the Tremadocian. allochthonous character is less emphasised than the lithofacies. In the Central Asian Orogenic Belt, for instance, the geology of Mongolia is subdivided “into COMPARISON OF THE 44 terranes: island arcs, continental margins, TECTONOMETAMORPHIC AND ophiolites, accretionary wedges, passive continental ISOTOPIC EVOLUTION OF THE TERRANES margins, microcontinents, turbidite overlap basins and continental margin arcs” (Windley et al., 2001: 825) – TECTONOMETAMORPHIC AND AGE PATTERN a very high number of possible terranes, indeed. In NVL, the exotic, allochthonous character of the It is obvious that a major structural break and a different lithotectonic units was pronounced when step in the metamorphic grade have to be located defining the terrane model. The prominent faults between the Wilson and the Bowers terranes, whereas separating the terranes were eye-catching and the structural and metamorphic history of the Bowers interpreted as major sutures. But a condition sine qua and Robertson Bay terranes is very similar. The non is that these faults are related to the terrane Wilson Terrane reveals a wide range of metamorphic accretion in the Early Palaeozoic. Some striking facts, grades from low grade to granulite facies conditions. however, seem to question the former terrane model. In contrast, the units of the Bowers and the Robertson These will be discussed in the following paragraphs. Bay terranes reached only very low- to locally low- grade conditions. The Wilson Terrane shows polyphase deformation OLISTOLITHS AND OLISTOSTROMES with generally E to NE directed kinematics during the (INCLUDING SEDIMENTARY MELANGES) peak metamorphic conditions. This is consistent with a westward directed subduction during the Ross Both the Bowers and Robertson Bay supergroups Orogeny. At least 3 phases of folding have been contain olistoliths and olistostromes, which can yield recognised. In contrast, the Bowers and the Robertson important information on the hinterland evolution of Bay terranes reveal a rather simple and uniform clastic rocks. Exotic blocks mainly consisting of structural pattern which involves open folds and limestones are reported from different places on both thrusts with a dominating E to NE directed tectonic sides of the Bowers and Robertson Bay terranes transport. boundary, indicating a similar geotectonic setting for The different structural levels of the both units. metasedimentary rocks of the Wilson Terrane reveal a According to Bradshaw & Laird (1983), carbonate maximum Cambrian sedimentation age suggested by blocks and olistostromes are present in the turbiditic recent age determinations of detrital zircons (Henjes- portions of the Molar Formation of the Sledgers Kunst & Schüssler, 2003 and references therein). The Group in the lower Carryer Glacier area, the source minimum age of the metamorphic overprint is given of which is suggested to be located somewhere to the by the intrusion of the Granite Harbour Intrusive NE and ENE. Based on the clast spectra, both an Complex at 480-490 Ma. island arc and continental source are assumed. A The age of the Molar Formation of the Bowers possible source could be, for instance, a carbonate Terrane is Middle Cambrian according to fringe of the Cambrian Bowers arc. palaeontological (Wolfart, 1994; Cooper et al., 1996) One of the more spectacular olistoliths is present and recent SHRIMP zircon ages (Bassett et al., 2002). at Reilly Ridge in the eastern Lanterman Range. For the Robertson Bay Group, a maximum Late There, Laird & Bradshaw (1983) reported large Cambrian to Early Ordovician sedimentation age is shallow-marine limestone blocks within mudstones of indicated by recent age determinations of detrital the Spurs Formation of the overlying Mariner Group zircons (Ireland et al., 1998; Fioretti et al., 2003), and bound to channel-like breccia horizons shed from a by Ar-Ar laser dating of detrital mica (Henjes-Kunst, continental source area in the SW and SE (Laird et 2003). al., 1982; Wright, 1985). Although Bradshaw & Laird (1983) mention carbonate olistostromes in the Sledgers Group, they TERRANES OT NOT TERRANES? suspect them conspicuously to be absent in the Robertson Bay Group. However, Wright et al. (1984) As defined by Irwin (1972) and in Jackson (1997), described limestone olistoliths (10 cm to 2 m in the term “terrane“ indicates an allochthonous diameter) of Latest Cambrian to Earliest Ordovician Revision of the Terrane Model of Northern Victoria Land 59 in age within turbidites and hemipelagic shales from The boundary between the Robertson Bay and Handler Ridge in the Robertson Bay Terrane (Handler Bowers terranes Formation). Downslope movements from a carbonate The Millen Schists separate the Bowers and the shelf were postulated but it was emphasized that no Robertson Bay terranes and border the eastern side of such shelf of the same age is known in the areas the Leap Year Fault (GANOVEX Team, 1987). They nearby. may involve rocks of both terranes, e.g. turbidites of Since the Molar, Mariner, and Handler olisto- the Robertson Bay Group and clastic and volcanic stromes and olistoliths differ significantly in their rocks of the Bowers Supergroup (Bradshaw et al., ages, lithological details, source areas of the detritus, 1985). These latter findings postulate that rocks of the as well as fauna and palaeoecological characteristics, Bowers Supergroup are also present east of the Leap they naturally do not correlate in the stratigraphic Year Fault, i.e. within the Robertson Bay Terrane. The sense. However, they support arguments for or against relationship between the Robertson Bay Group and the terrane nature of the Bowers and Robertson Bay the Bowers Supergroup was often discussed (e.g. lithotectonic units and the accretion history of the E- Wright & Findlay, 1984, Adams & Kreuzer, 1984). Gondwanan palaeo-Pacific margin in Early Palaeozoic Wright & Findlay (1984) suggested that the sequence times (see discussion chapter). at Handler Ridge in the Robertson Bay Terrane is in fact equivalent to the Bowers Supergroup. Although these authors had no definitive prove for this model, they discussed the consequences derived from this THE SO-CALLED “TERRANE BOUNDARIES” observation, which imply that the Robertson Bay Group would conformably underlie the Bowers The rocks of the Bowers and Robertson Bay Supergroup and both units would share a common terranes are generally of very low-grade metamorphic origin and general tectonic history. grade. Low-grade facies is only reached near the This is in line with the tectonic evolution boundaries of both units. The rocks of both the proposed by Findlay (1986), who interpreted the Bowers Supergroup and the Robertson Bay Group Millen Schists as the basal mylonitic reverse shear partly differ in their composition but not in their zone marking the contact between overlying structural style and metamorphic overprint. This Robertson Bay metasedimentary sequences and the indicates that the major upright fold structures underlying metasedimentary and metavolcanic rocks observed in the two units and metamorphic overprint of the Bowers terrane. This is also in line with the occurred after accretion, but it does not automatically aforementioned view that the Leap Year Fault cannot imply that the two units were always together. represent a terrane boundary neither a major suture, However, the compositional differences at the time of but rather a reverse shear zone developed during a deposition of the Bowers and the Robertson Bay major shortening episode linked to the development clastic rocks and the distribution of volcanic detritus of the Robertson Bay fold-and-thrust belt. The actual are indicative of a separate tectonic history prior to terrane boundary is located within the Millen shear involvement of the two units in the accretion process zone. The main consequence of this statement is that at the active margin. The structural and metamorphic the Robertson Bay low-grade metasedimentary rocks similarities suggest furthermore that the far more are not part of a distinct tectonic block or an exotic dominant and obvious structural and metamorphic terrane accreted onto the East Gondwana active break is located between the Wilson and Bowers margin. Consequently, there are no hints of the terranes (i.e. at the Lanterman Fault Zone) rather than closing of an ocean of Cambrian or older age between the Bowers and Robertson Bay terranes. This separating the Robertson Bay Terrane from the major break is not only evident in terms of the Bowers Terrane. They rather represent continuous tectonometamorphic histories of the two units, but turbiditic sedimentation in an accretionary setting that especially by the tectonic zone of ultrahigh-pressure existed at the palaeo-Pacific Gondwanan margin rocks on the western (i.e. towards the Wilson terrane) during the Palaeozoic in analogue to the Lachlan Fold of the Wilson-Bowers boundary zone in the Belt in Australia (e.g. Ferguson, 2003). Lanterman Range. In earlier descriptions of the tectonic history of NVL, the importance of the The boundary between the Wilson and Bowers different lineaments separating the terranes was terranes recognised: The Lanterman Fault was interpreted to The Lanterman conglomerate, Husky con- separate the Rennick Trough Tectonic Zone from the glomerate, and Black Spider Greenschists Bowers Trough Tectonic Zone which itself was (GANOVEX Team, 1987, and references therein) separated from the Robertson Bay Tectonic Zone by delineate the boundary between the Wilson and the Leap Year Fault (Grindley & Oliver, 1983). In the Bowers terranes and parallel the Lanterman Fault. following years, schist belts were mapped which are Here, we have indeed a boundary separating distinct associated with the terrane boundaries, so for example tectonic blocks, which are different in structural style, the Millen Schists or the Black Spider Greenschists. metamorphic grade, geochemistry, and age. The 60 N.W. Roland et al. importance of this boundary is emphasised by the 2003). Old structural trends and younger, at least occurrence of UHP eclogitic lenses (Ghiribelli et al., post-Jurassic trends seem to coincide or overlap to 2002), as well as by slices of mafic and ultramafic some degree (Salvini et al., 1997; Rossetti et al., rocks which proved to represent ocean floor material. 2003). Capponi et al. (1999) distinguish four main tectonic In the past, the main NW-SE striking lineaments phases for this zone: (1) west over east thrusting of that dominate the structural trends in NVL were Ross age (around 500 Ma); (2) sinistral strike-slip thought to have formed during W-directed subduction shearing which may be related to the Ross Orogeny associated with magmatic growth and accretion at the or the so-called “Borchgrevink” Orogeny (around 360 Palaeo-Pacific active continental margin of Gondwana Ma); (3) large-wavelength folding of late-Ross or during the Ross Orogeny in Neoproterozoic to Early “Borchgrevink” age; (4) Cenozoic brittle tectonics, Palaeozoic times (e.g. Kleinschmidt & Tessensohn, expressed by small to km-scale structures. On the 1987; Bradshaw, 1989; Stump, 1995). However, other hand, based on integrated structural and fission timing and direction of terrane docking were track apatite thermochronology, Rossetti et al. (2003) discussed in different ways. The accretion of the three terranes at the East Antarctic Craton in one step was documented that the Lanterman Fault Zone favoured by Kleinschmidt & Tessensohn (1987), or in corresponds to a broad zone of distributed and two stages involving early Palaeozoic accretion of the partitioned right-lateral shearing, activated at the Wilson Terrane at the Precambrian shield followed by Pacific coast of NVL at about 40-50 Ma. The same Devonian to Carboniferous accretion of the Bowers authors also argued that Cenozoic right-lateral slip and Robertson Bay terranes at the Wilson Terrane along the Lanterman Fault might have had a (Borg & Stump 1987). Orthogonal versus oblique fundamental control on the final assembly of the convergence scenarios were also proposed for the Wilson Terrane against the Bowers-Robertson Bay early Palaeozoic subduction at the Palaeo-Pacific assembly (Admiralty Block in Tessensohn, 1994). active margin of Gondwana, including the effect of This is consistent with the definition of a terrane slab roll back (Matzer, 1995; Finn et al., 1999; boundary, which in this case is overprinted by later Ferraccioli et al., 2002). tectonics. Nevertheless, post-Ross deformation was reported by Laird & Bradshaw (1981), Grindley & Oliver The boundary between the Wilson Terrane and the (1983), and Roland & Tessensohn (1987). The latter Mawson Block authors described occurrences of folds and thrusts in When introducing the terrane concept, the Wilson Beacon as well as in Ferrar rocks along the western Metamorphics were considered to represent a distinct flank of the Lanterman Range and strike-slip tectonics terrane (e.g. Bradshaw et al., 1985; Weaver et al., were thought to be the reason for these brittle 1984). The medium- to high-grade rock units and the deformations. However, further studies on the tectonic related granites and migmatites of the Wilson Terrane position of the Lanterman Range and especially on can well be regarded as the platform area of a craton, the nature of the terrane boundaries were required to whilst the Mawson Block represents the shield part of better elucidate this Meso-Cenozoic tectonic the craton (the definitions of platform, shield, and evolution. Based on the interpretation of offshore craton used as in Jackson 1997). Being the seismic reflection data in the Ross Sea (Fig. 1), overprinted multiple deformed margin of Gondwana´s Salvini et al. (1997) postulated post-Oligocene large- Palaeo-Pacific rim, there is no reason to postulate a scale right-lateral strike-slip motions reactivating both distinct Wilson Terrane. Similar arguments were used the inherited Palaeozoic NW-SE-trending structures already by Tessensohn (1997), who states that no and terrane boundary faults (e.g. Ferraccioli and inboard terrane boundary is exposed against the Bozzo, 1999). According to Salvini et al. (1997), the Precambrian East Antarctic Craton. Cenozoic tectonic pattern thus results in an array of major NW-SE dextral displacement zones abutting in the Ross Sea into a major N-S transtensional KINEMATIC AND DEFORMATION EVOLUTION deformation belt. As a matter of fact, late Cenozoic OF NVL partitioned NW-SE striking right-lateral strike-slip tectonics has been recognised in NVL (Storti et al., At the Pacific coast of the Antarctic continent, at 2001; Rossetti et al., 2002; 2003), whereas N-S least in the areas (from east to west) of the Pennell, striking right-lateral transtensional tectonics dominates Oates, and George V coasts, NW-SE to NNW-SSE the Cenozoic structural pattern in southern Victoria trending lineaments dominate both morphology and Land (Wilson, 1995; Rossetti et al., 2000). Moreover, geology. Even the large Rennick and Matusevich a clear relationship is established between Cenozoic glaciers follow more or less this trend as well as denudation, activation and connectivity of the various some aeromagnetic anomalies including the huge dextral strike-slip fault systems cutting through NVL Matusevich anomaly which parallels the Matusevich during the Cenozoic (Rossetti et al., 2003). These Glacier (Damaske et al., 2003, Ferraccioli et al., results attest persistence through time of dextral Revision of the Terrane Model of Northern Victoria Land 61 shearing by ca. 34 Ma and suggest a possible the two units have quite different geological and connection between NW-SE striking strike-slip particularly palaeogeographic histories. The Bowers faulting and active tectonics in the Ross Sea region Supergroup comprises three major lithological groups, (namely Victoria Land and the Ross Sea). This is the Sledgers, the Mariner, and the Leap Year Group. confirmed by earthquakes registered in the lower The volcanic, volcaniclastic and turbiditic rocks of the Matusevich Glacier area in 1952 and in the lower lower Sledgers Group formed in a rather deeper Rennick Glacier area in 1974 (M 4.9; 33 km depth) slope-environment close to an intra-oceanic island arc (Roland & Tessensohn, 1987). During the Joint in ?Early to Middle Cambrian times. Partly oolithic German-Italian1999-2000 Antarctic Expedition, carbonate olistostromes can probably be related to another earthquake (M 3.1; 23.5 km depth) was carbonate fringes around this arc in a rather wave- recorded in the lower Rennick Glacier area on dominated regime. These rocks grade upwards into December 30th 1999 at 6.33 UTC (Cattaneo et al., the regressive series of the Middle-Late Cambrian 2001), probably connected to the eastern boundary shallow-marine Mariner and the however not-well fault of the Rennick Graben or the Lanterman Fault. constrained Late Cambrian to ?Early Ordovician We propose that the present arrangement is not continental-fluviatile Leap Year Group. entirely the result of Cenozoic tectonics, but that it Sedimentological features in the Sledgers Group has strongly overprinted the older Ross age large- indicate detrital transport towards the SW to WSE, scale structures (Rossetti et al., 2003). which contrasts with the transport directions in the Mariner and Leap Year groups suggesting a continental source area somewhere in the SW (e.g. THE GEOLOGICAL DEVELOPMENT OF Laird et al. 1982). Since the accretion of this intra- NORTHERN VICTORIA LAND REVISITED oceanic arc to the active E-Gondwanan margin can roughly be dated to the Late Middle Cambrian (see In the light of the results from the Joint German- chapter 2), we suggest that the deposition of Italian Antarctic Expedition 1999-2000, the particularly the Leap Year Group and possibly in evolutionary model for the Early Palaeozoic tectonic parts the Mariner Group as well post-dates accretion. accretion in the NVL sector of Antarctica needs in This is underlined by the contrasting sedimentary our view to be modified. In particular, according to transport directions and the different sources of the new results of e.g. Rossetti et al. (2003), the detrital material of the rocks in the Sledgers and present trace of the Lanterman Fault is an expression Mariner/Leap Year groups. of Cenozoic right-lateral tectonics, which has strongly While the Mariner Group is characterised by overprinted the Early Palaeozoic structural and common limestone and widely distributed carbonate metamorphic edifice as well as possible Late cobble rudites (e.g. in the Mariner Glacier in the SE), Palaeozoic and as well Mesozoic tectonic features there is practically no carbonate in the Robertson Bay (e.g., structures related to the so-called Group, apart from the Handler Formation, which is “Borchgrevink” event [e.g. Capponi et al., 2002 and significantly younger (i.e. Latest Cambrian to Earliest references therein]; structures related to the break-up Ordovician). If the interpretation of the Handler of Gondwana [e.g. Tessensohn 1994]). Cenozoic slip Formation as an exotic block of shallow-marine along this major, NW-SE striking fault might be still limestone derived from a southwesterly located source active even today, as suggested by the registered area is correct, it would, in our opinion, indicate that seismic activity in the lower Rennick Glacier area. the sedimentary matrix and thus the Robertson Bay Accordingly, the exact trace of the terrane boundaries sediments are at least in great parts of the same age need to be revised and the role of Cenozoic overprint or even younger. This would place a great part of the has to be taken into account in any tectonic Robertson Bay turbidites in the Late Cambrian and reconstruction of the Early Palaeozoic structural Early Ordovician rather than way back into the evolution. For instance, the exact trace of the Ross- Cambrian. A maximum Late Cambrian to Early orogenic boundaries (e.g., the Wilson-Bowers UHP Ordovician age of deposition is also suggested by zone, the Millen Schist zone in the Bowers-Robertson recent age data of detrital zircons (Ireland et al., Bay boundary region) strike approximately NW-SE 1998; Fioretti et al., 2003) and Ar-Ar laser ages of and thus indicate an acute angle to the main, NNW- detrital mica (Henjes-Kunst, 2003). Furthermore, SSE trending course of the Lanterman Fault. In the sedimentological (Wright, 1981; Wright et al., 1984) area of the Lanterman Range, these inherited and more recent geochemical evidence (Henjes-Kunst structures are re-used as a contractional step-over or & Schüssler, 2003) emphasize that the source area of duplex structure caused by right-lateral Cenozoic the Robertson Bay turbidites was located in the area motion along the Lanterman Fault (e.g. Rossetti et al., of the evolving Ross-orogenic belt in the W to SW 2002, 2003). rather than a suspect continental landmass in the E The afore-mentioned lithological, palaeontological, (e.g. Gibson & Wright, 1985; Matzer 1995). The geochronological, and sedimentological features of the arguments favouring a Late Cambrian-Early Bowers and Robertson Bay supergroups indicate that Ordovician age would also suggest that Robertson 62 N.W. Roland et al.

Fig. 2 – Comparison of the former three-terrane model and the proposed new model with alternative terminology.

Bay deposition was roughly synchronous to the 2003). We hence think that the term “terrane” is not further inland continental-fluviatile Leap Year Group, applicable for the Robertson Bay lithotectonic unit. which probably represented a molasse-type The term “terrane” should not be applied for the sedimentary sequence deposited after accretion of the Wilson Terrane either. This lithotectonic unit formed Bowers Terrane. in Early Palaeozoic times by reorganization of the Based on our comparison of the Bowers and geotectonic pattern at the palaeo-Pacific margin of Robetson Bay lithotectonic units, we think that the Gondwana. The former passive margin developed into term “terrane” is applicable for the Bowers Terrane an active one by the onset of west-directed only but not for the outboard turbidite sequence of subduction of the Palaeo-Pacific lithosphere under the the Roberson Bay Group. The Bowers Terrane indeed East Antarctic Craton involving the formation of a represents a fault-bounded lithotectonic unit, which magmatic arc (Granite Harbour Intrusives), an formed as an intra-oceanic arc of ?Early to Middle accretionary wedge, and both regional and HP/LT- Cambrian age somewhere in the palaeo-Pacific ocean metamorphism (e.g. Ricci et al., 1997; Finn et al., off the E-Gondwanan margin. After cessation of 1999). Since the Wilson Terrane was never welded to subduction under the Bowers arc, the Bowers Terrane the continent, the term “terrane” is once again was attached to the active Gondwana margin in the obsolete and we introduce the name Wilson Mobile Late Middle Cambrian (Bassett et al., 2002). It is Belt (Fig. 2). separated from the Wilson Terrane by a narrow belt The geological development of NVL can be consisting of mafic to ultramafic rocks containing described in the following steps: coesite-bearing eclogite lenses within a quartzo- - Onset of the subduction process in the Earliest feldspathic matrix (Ricci et al., 1997; Ghiribelli et al., Palaeozoic and establishment of an active 2002). The latter rock assemblage is interpreted as the continental margin result of subduction of palaeo-Pacific crust under the - Formation of a thick orogenic wedge due to Gondwana active margin and was exhumed after subduction, turbiditic sedimentation in a trench, collision of the Bowers Terrane and subsequent uplift and magmatic growth (including UHP of the thickened crust (Goodge & Dallmeyer, 1996). metamorphism on deeply subducted continental Following the accretion and uplift of the Bowers and oceanic materials) and, possibly, subsequent Terrane, the turbidite sequence of the Robertson Bay collapse-related exhumation of its deep-seated Group was deposited outboard of the margin in an portions accretionary environment and both the Bowers and - Progressive retreat of the subduction boundary the accreted turbidites became involved in Ross-age - Island arc development of the Bowers Supergroup imbricate deformation, a tectonic scenario comparable above an Early Palaeozoic intra-oceanic to the Lachlan Fold Belt in SE Australia (Ferguson, subduction zone located further E of the active Revision of the Terrane Model of Northern Victoria Land 63

continental margin, which includes conglomerates, terranes, northern Victoria Land, Antarctica. In: Roland quartzites, limestones, turbidites, and volcanics of N.W.(ed), German Antarctic North Victoria Land Expedition 1982 / 83, GANOVEX III, Vol. I., Geologisches Jahrbuch, B tholeiitic composition, i.e. primitive island arc or 60, 265 – 288. back-arc but not MORB affinities according to Bassett K.N., Weaver S., Bradshaw J.D. & Ireland T., 2002. Dating Weaver et al. (1984) the accretion of the Cambrian intra-oceanic arc, Bowers - Collision of the Bowers island arc at the East Terrane, northern Victoria Land, Antarctica. Gondwana 11 – Correlations and connections, Programme and Abstracts, Gondwanan margin, and formation of the Wilson- Christchurch. Bowers suture zone. Borg, S.G. & DePaolo, D.J., 1994. Laurentia, Australia, and - Continuing outboard migration of the subduction Antarctica as a Late Proterozoic supercontinent: Constraints zone and formation of the accretionary wedge of from isotope mapping. Geology, 22, 307-310. Borg S.G. & Stump E., 1987. Palaeozoic magmatism and the Robertson Bay Group after docking of the associated tectonic problems of Northern Victoria Land, Bowers Arc Terrane involving turbiditic Antarctica. In: McKenzie, G.D. (ed.), Gondwana Six: sedimentation including large olistoliths (e.g. Structure, Tectonics and Geophysics. Geophys. Monogr. Handler Fm.) in analogy to the Australian Lachlan American Geophys. Union, 67-75. Bradshaw, J.D., 1989. Terrane boundaries in northern Victoria Fold Belt (e.g. Ferguson, 2003). Land. Memorie della Società Geologica Italiana, 33, 9-15. - Large-scale Cenozoic strike-slip dominated Bradshaw M.A., 1991. The Devonian Pacific margin of Antarctica.- tectonics is responsible for the final tectonic In: Thomson M.R.A., Crame J.A. Thomson J.W. (eds.), architecture of the Wilson Mobile Belt with the Geological evolution of Antarctica, Cambridge University Press, Cambridge, 193-197. arc/fore-arc system represented by the Bowers and Bradshaw J.D. & Laird M.G., 1983. The pre-Beacon geology of Robertson Bay units. Northern Victoria Land: A review.- In: Oliver R.L., James P.R. Accordingly, we suggest the following & Jago J.B. (eds.), Antarctic Earth Science, 98-101. lithotectonic major units (Fig. 2) for the Ross- Bradshaw J.D., Weaver S.D. & Laird M.G., 1985. Suspect Terranes and Cambrian Tectonics in Northern Victoria Land, Antarctica. orogenic geological evolution of NVL from west to In: Howell D.G. (ed.), Tectonostratigraphic Terranes of the east: Circum-Pacific Region, Circum-Pacific Conference for Energy - The Precambrian East Antarctic Craton or Mawson and Mineral Resources, Earth Science Series, 1, 467-479. Block Capponi G., Castelli D., Fioretti A.M. & Oggiano G., 1997. Geological mapping and field relationships of eclogites from - The Wilson Mobile Belt, representing the re- the Lanterman Range (northern Victoria Land, Antarctica). In: organised former platform area of the Precambrian Ricci C.A. (ed.), The Antarctic Region: Geological Evolution craton with polyphase metamorphic basement and Processes. Terra Antartica Publication, Siena, 219-225. intruded by the late-orogenic Granite Harbour Capponi G., Castorina F., Di Pisa A., Meccheri M., Petrini R. & Villa I.M., 2002. The meta-igneous rocks of the Barber Glacier Complex area (northern Victoria Land, Antarctica): a clue to the - The Bowers Arc Terrane, representing a Cambrian enigmatic Borchgrevink Orogeny? In: Gamble J., Skinner island arc association and co-genetic slope D.N.B. & Henrys S. (eds.), Antarctica at the close of a sediments accreted to the East Gondwana active millennium. Royal Society of New Zealand Bulletin, 35, 99- 104. margin Capponi G., Crispini L. & Meccheri M., 1999. Structural history - The Robertson Bay Accretionary Wedge involving and tectonic evolution of the boundary between the Wilson and continuous turbiditic sedimentation at the East Bowers terranes, Lanterman Range, northern Victoria Land, Gondwana active margin subsequent to the Antarctica. Tectonophysics, 312, 249-266. Cattaneo M., Chiappini M. & De Gori P., 2001. Seismological Bowers Arc Terrane accretion. experiment. Terra Antartica Reports, 5, 29-43, Siena. Cooper R.A., Begg J.G. & Bradshaw J.D., 1990. Cambrian trilobites from the Reilly Ridge, northern Victoria Land, Acknowledgements – This paper is a contribution to the Antartica. New Zealand Journal of Geology and Geophysics, joint German-Italian GANOVEX VIII – ITALIANTARTIDE XV 33, 55-66. Expedition 1999-2000. Logistic and financial support was Cooper R.A., Jago, J.B. McKinnon D.J. Simes J.E. & Braddock P.E., 1976. Cambrian fossils from the Bowers Group, northern provided by BGR and PNRA. A.L. and F.R. are indebted Victoria Land, Antartica. New Zealand Journal of Geology and to BGR for invitation to the programme. A.L. thanks Geophysics, 19 (2), 283-288. Deutsche Forschungsgemeinschaft for financial support Cooper R.A., Jago J.B. & Begg J.G., 1996. Cambrian trilobites (grants KL 429/18-1 to 3) and Alfred-Wegener-Institute for from Northern Victoria Land, Antarctica, and their stratigraphic Polar and Marine Research, Bremerhaven, for polar implications. New Zealand Journal of Geology and Geophysics, equipment. F.R. acknowledges a fellowship of PNRA at 39, 363-387. Siena University and thanks R. Funiciello and F. Salvini for Damaske, D., Ferraccioli, F. & Bozzo, E., 2003: Anomaly investigations along the Antarctic coast between Yule Bay and continuous encouragement and support. The reviewers J. Mertz Glacier. Terra Antartica, 10, 85-96. Bradshaw and F. Talarico are gratefully acknowledged for Dow J.A.S. & Neall V.E., 1974. Geology of the lower Rennick providing constructive suggestions, which improved an Glacier, northern Victoria Land, Antarctica. New Zealand earlier version of the manuscript. Journal of Geology and Geophysics, 17 (3), 659 – 714. Encarnación J. & Grunow A., 1996. Changing magmatic and tectonic styles along the paleo-Pacific margin of Gondwana and the onset of Early Palaeozoic magmatism in Antarctica. REFERENCES Tectonics, 15 (6) 1325-1341. Ferguson C.L., 2003. Ordovician-Silurian accretion tectonics of the Adams C.J. & Kreuzer H., 1984. Potassium-argon age studies of Lachlan Fold Belt, southeastern Australia. Australian J. Earth slates and phyllites from the Bowers and Robertson Bay Sci., 50, 475-490. 64 N.W. Roland et al.

Ferraccioli F. & Bozzo E., 1999. Inherited crustal features and Sciences (ISAES IX), Antarctic Contributions to Global Earth tectonic blocks of the Transantarctic Mountains: An Sciences, Programme and Abstracts. Terra Nova, 2003/04, 150- aeromagnetic perspective (Victoria Land, Antarctica). Journal 151. of Geophysical Research, 104, 25297-25319. Henjes-Kunst F., Roland N.W. & Dunphy J., 2003. SHRIMP-dating Ferraccioli F., Bozzo E. & Capponi G., 2002. Aeromagnetic and of high-grade metamorphic and igneous rocks from Oates Land gravity anomaly constraints for an early Palaeozoic subduction at the Pacific margin of the Transantarctic Mountains, system of Victoria Land, Antartica. Geophysical Research Antarctica.- In: Fütterer, D.H. (ed.), 9th Internat. Symp. on Letters, 29 (10), 1406. Antarctic Earth Sciences (ISAES IX), Antarctic Contributions Ferraccioli, F., Damaske, D., Bozzo, E. & Talarico, F., 2003. The to Global Earth Sciences, Programme and Abstracts. Terra Matusevich Aeromagnetic Anomaly over Oates Land Nova, 2003/04, 149-150. (Antarctica). Terra Antartica, 10, 221-228. Henjes-Kunst F., Roland N.W. & Dunphy J., 2004. SHRIMP dating Field B.D. & Findlay R.H., 1983. The sedimentology of the of high-grade migmatites and related granitoids from the Oates Robertson Bay Group, northern Victoria Land. In: Oliver, R.L., Coast area (East Antarctica): Evidence for a single high-grade James, P.R. & Jago, J.B. (eds.), Antarctic Earth Science, event of Ross-orogenic age. Terra Antartica, this volume. Australian Academy of Science, Canberra, 102-106. Henjes-Kunst F. & Schüssler U., 2003. Metasedimentary units of Findlay R.H., 1986. Structural geology of the Robertson Bay and the Cambro-Ordovician Ross Orogen in northern Victoria Land Millen terranes, northern Victoria Land, Antarctica. In: Stump and Oates Land: Implications for their provenance and E. (ed.), Geological investigations in Northern Victoria Land. geotectonic setting from geochemical and Nd-Sr isotope data. American Geophys. Union, Antarctic Research Ser., 46, 91-114. Terra Antartica, 10, 105-128. Finn C., Moore D., Damaske D. & Mackey T., 1999. Aeromagnetic Ireland T.R., Flöttmann T., Fanning C.M., Gibson G.M. & Preiss legacy of early Palaeozoic subduction along the Pacific margin W.V., 1998. Development of the early Palaeozoic Pacific of Gondwana. Geology, 27, 1087-1090. margin of Gondwana from detrital-zircon ages across the Fioretti A.M., Black P., Henjes-Kunst F. & Visonà D., 2003. Delamerian orogen. Geology, 26, 243-246. Detrital zircon age patterns from a large gneissic xenolith from Kleinschmidt G. & Tessensohn F., 1987. Early Palaeozoic westward Cape Phillips granite and from Robertson Bay Group directed subduction at the Pacific margin of Antarctica. In: metasediments, northern Victoria Land, Antartica. In: Fütterer McKenzie, G.D. (ed.): Gondwana Six: Structure, tectonics and D.K. (ed.), 9th Internat. Symp. on Antarctic Earth Sciences geophysics. Amer. Geophys. Union, Geophys. Monogr. Series, (ISAES IX), Antarctic Contributions to Global Earth Sciences, 40, 89-105. Programme and Abstracts. Terra Nova, 2003/04, 94-95. Kleinschmidt G., Tessensohn F. & Vetter U., 1987. Palaeozoic Gair H.S, Sturm A., Carryer S.J. & Grindley G.W., 1969. The accretion at the Paleopacific margin of Antarctica. geology of northern Victoria Land. Antarctic Map Folio Series, Polarforschung, 57, 1 8. American Geogr. Soc, New York. Folio 12, Pl. XII. Läufer A. & Rossetti F., 2001. Brittle deformation features in the GANOVEX-Team, 1987. Geological map of North Victoria Land, Rennick Glacier-Yule Bay area, Northern Victoria Land, Antarctica, 1:500000 - Explanatory Notes. In: Tessensohn F & Antarctica. Terra Antartica Reports, 5, 77-80, Siena. Roland N.W. (eds.), German Antarctic North Victoria Land Läufer A.L., Rossetti F., 2003. Late-Ross ductile deformation Expedition (GANOVEX III), Vol. 2, Geologisches Jahrbuch, B features in the Wilson Terrane of northern Victoria Land 66, 7-79. (Antarctica) and their implications for the western front of the Ghiribelli B., Frezzotti M.-L. & Palmeri R., 2002. Coesite in Ross Orogen. Terra Antartica, 10, 179-196. eclogites of the Lanterman Range (Antarctica): Evidence from Laird M.G. & Bradshaw J.D., 1981. Permian tillites of North textural and Raman studies. Eur. J. Mineral., 14, 355-360. Victoria Land, Antartica. In: Hambrey M.J. & Harland W.B. Gibson G., 1985. Lanterman Fault: Boundary between (eds.), Earth´s pre-Pleistocene glacial record. Cambridge, 237- allochthonous terranes, northern Victoria Land, Antarctica. 240. Third circum-Pacific terrane conference, Abstr., Geol. Soc. Laird M.G. & Bradshaw J.D., 1983. New data on the Lower Australia, 14. Palaeozoic Bowers Supergroup, Northern Victoria Land. In: Gibson G., Tessensohn F. & Crawford A.R.,1984. Bowers R.L. Oliver, P. R. James & J. B. Jago (eds.), Antarctic Earth Supergroup rocks west of the Mariner Glacier and possible Science, 123 126, Australian Academy of Science, Canberra. greenschist facies equivalents. In: Roland, N.W. (ed.), German Laird M.D., Bradshaw J.D. & Wodzicki A., 1982. Stratigraphy of Antarctic North Victoria Land Expedition 1982/83 GANOVEX the Upper Precambrian and Lower Palaeozoic Bowers III, Vol. I., Geologisches Jahrbuch, B 60, 289 318. Supergroup, northern Victoria Land, Antarctica. In: Craddock Gibson G.M. & Wright T.O.,1985. Importance of thrust faulting in C. (ed.). Antarctic Geoscience, Madison, Wisconsin (Univ. the tectonic development of northern Victoria Land, Antarctica. Wisconsin Press), 535-542. Nature, 315 (6019), 480483. Matzer S., 1995. Palaeozoic accretion at the Paleopacific margin of Goodge J.W., 2003. From Rodinia to Gondwana: supercontinent Antarctica in North Victorialand – P-T-D-history and evolution in the Transantarctic Mountains. In: Gamble J., deformation mechanisms in the Bowers Terrane. Berichte zur Skinner D.N.B. & Henrys S. (eds.). Antarctica at the close of a Polarforschung, 173, 1-234 (in German). millennium. Royal Soc. New Zealand Bull., Wellington, 35, 61- Ricci C.A., Talarico F. & Palmeri R., 1997. Tectonothermal 74. evolution of the Anarctic Paleo-Pacific margin of Gondwana: a Goodge J.W. & Dallmeyer R.D., 1996. Contrasting thermal northern Victoria Land perspective. In: Ricci, C.A. (ed.), The evolution within the Ross Orogen, Antarctica: Evidence from Antarctic Region: Geological Evolution and Processes. Terra mineral 40 Ar/39 Ar ages. J. Geology, 104, 435-458. Antartica Publication, Siena, 213-218. Grindley G.W. & Oliver P.J., 1983. Post-Ross Orogeny Roland N.W. & Tessensohn F., 1987. Rennick faulting - an early cratonisation of North Victoria Land. In: Oliver R.L., James phase of Ross Sea Rifting. In: Tessensohn F. & Roland N.W. P.R. & Jago J.B (eds.), Antarctic Earth Science, Australian (eds.), German Antarctic North Victoria Land Expedition Academy of Science, Canberra, 133-139. (GANOVEX III), Vol. 2, Geologisches Jahrbuch, B66, 203 – Irwin W.P., 1972. Terranes of the western Palaeozoic and Triassic 229. belt in the southern Klamath Mountains, California. In: Rossetti F., Storti F. & Salvini F., 2000. Cenozoic noncoaxial Geological Survey research, 1972. U.S. Geological Survey transtension along the western shoulder of the Ross Sea, Professional Paper, 809-C, C103-C111. Antarctica, and the emplacement of McMurdo dyke arrays. Jackson J.A. (ed.), 1997. Glossary of Geology, 4. ed., American Terra Nova, 12(2), 60-66. Geological Institute, Alexandria, Virginia, 769 p. Rossetti F., Lisker F., Storti F. & Läufer A.L., 2003. Tectonic and Henjes-Kunst F., 2003. Single-crystal Ar-Ar laser dating of detrital denudational history of the Rennick Graben (North Victoria micas from metasedimentary rocks of the Ross orogenic belt at Land): Implications for the evolution of rifting between East the Pacific margin of the Transantarctic Mountains, Antartica. and West Antarctica. Tectonics, 22(2), 1016, In: Fütterer, D.H. (ed.), 9th Internat. Symp. on Antarctic Earth doi:10.1029/2002TC001416. Revision of the Terrane Model of Northern Victoria Land 65

Rossetti F., Storti F. & Läufer A.L., 2002. Brittle architecture of the for the Early Palaeozoic tectonic evolution of northern Victoria Lanterman Fault and its impact on the final terrane Land, Antarctica. Earth and Planetary Science Letters, 68, amalgamation in North Victoria Land, Antarctica. Journal of 128 140. the Geological Society, London, 159, 159-173. Wilson T.J., 1995. Cenozoic transtension along the Transantarctic Salvini F., Brancolini G., Busetti M., Storti F., Mazzarini F., & Mountains – West Antarctic Rift boundary, southern Victoria Coren, F., 1997. Cenozoic right-lateral strike-slip tectonics in Land, Antarctica. Tectonics, 14(2), 531-545. the Ross Sea Region, Antarctica. In: Ricci, C.A. (ed.), The Windley B.F., Badarch G., Cunningham W.D., Kröner A., Buchan Antarctic Region: Geological Evolution and Processes, Terra A.C., Tomurtogoo, O. & Salnikova, E.B., 2001. Subduction- Antartica Publication, Siena, 585-590. accretion history of the Central Asian Orogenic Belt: Storti F., Rossetti F. & Salvini F., 2001. Structural architecture and Constraints from Mongolia. Gondwana Research, 4(4), 825- displacement accommodation mechanism at the termination of 826. the Priestley Fault, northern Victoria Land, Antarctica. Wodzicki A. & Roberts R., 1987. Geology of the Bowers Tectonophysics, 341(1-4), 141-161. Supergroup, central Bowers Mountains, northern Victoria Land. Stump E., 1976. On the Late Precambrian-Early Palaeozoic In: Stump E. (ed.), Geological investigations in northern metavolcanics and metasedimentary rocks of the Queen Maud Victoria Land, Antarctic Research Series, 46, 39-68. Mountains, Antarctica, and a comparison with rocks of similar Wolfart R.,1994. Middle Cambrian Faunas (Brachiopoda, Mollusca, age from southern Africa. Rep. Inst. Polar Studies Ohio State Trilobita) from exotic limestone blocks, Reilly Ridge, North Univ., 62. Victoria Land, Antarctica; their biostratigraphic and Stump E., 1995. The Ross Orogen of the Transantarctic Mountains. Palaeobiogeographic significance. Geologisches Jahrbuch, B84, Cambridge University Press, Cambridge, 284 pp. 1-161. Stump E., Laird, M.G., Bradshaw J.D., Holloway J.R., Borg S.G. Wright T.O., 1981. Sedimentology of the Robertson Bay Group, & Lapham, K.E., 1983. Bowers graben and associated tectonic North Victoria Land, Antarctica. Geologisches Jahrbuch, B41, features cross northern Victoria Land, Antarctica. Nature, 304 (5924) 334-336. 127 - 138. Talarico F., Ghiribelli B., Smith-Siddoway C., Palmeri R. & Ricci, Wright T.O., 1985. Late Precambrian and early Paleozoic tectonism C.A., 1998. The northern Victoria Land segment of the and associated sedimentation in northern Victoria Land, Antarctic paleo-Pacific margin of Eastern Gondwana: New Antarctica. Geological Society of America Bulletin, 96, 1332- constraints from the Lanterman and Mountaineer ranges. Terra 1339. Antartica, 5, 245-252. Wright T.O. & Findlay R.H., 1984. Relationships between the Tessensohn F., 1994. The Ross Sea Region, Antarctica: Structural Robertson Bay Group and the Bowers Supergroup - New interpretation in relation to the evolution of the Southern progress and complications from the Victory Mountains, Ocean. Terra Antartica, 1, 553-558. northern Victoria Land. In: Roland, N.W. (ed.), German Tessensohn F., 1997. Shackleton Range, Ross Orogen and SWEAT Antarctic North VictoriaLand Expedition 1982/83, GANOVEX Hypothesis. In: Ricci C.A. (ed.), The Antarctic region: III, Vol. I., Geologisches Jahrbuch, B60, 105-116. Geological evolution and processes. Terra Antartica Publication, Wright T.O., Ross R.J. jr. & Repetski J., 1984. Newly discovered Siena, 5-12. youngest Cambrian or oldest Ordovician fossils from the Weaver S.D., Bradshaw J.D. & Laird M.G., 1984. Geochemistry of Robertson Bay terrane (formerly Precambrian), northern Cambrian volcanics of the Bowers Supergroup and implications Victoria Land, Antarctica. Geology, 12, 301305.