U.S. Geological Survey and The National Academies; USGS OF-2007-1047, Short Research Paper 102; doi:10.3133/of2007-1047.srp102 Triassic-Jurassic sediments and multiple volcanic events in North Victoria Land, Antarctica: A revised stratigraphic model R. Schöner, 1 L. Viereck-Goette, 1 J. Schneider, 2 and B. Bomfleur 3 1 Friedrich-Schiller-Universität Jena, Institut für Geowissenschaften, Burgweg 11, 07749 Jena, Germany (robert.schoener@uni-jena.de ; lothar.viereck-Goette@uni-jena.de) 2 TU Bergakademie Freiberg, Institut für Geologie, Bernhard-von-Cotta Str. 2, 09596 Freiberg, Germany (schneidj@geo.tu-freiberg.de) 3 Westfälische Wilhelms-Universität Münster, Geologisch-Paläontologisches Institut, Hindenburgplatz 57, 48143 Münster, Germany (bennibomfleur@gmx.de) Abstract Field investigations in North Victoria Land, Antarctica during GANOVEX IX (2005/2006) allow the revision of the Triassic-Jurassic stratigraphy of ~300 m thick continental deposits in between the crystalline basement and the Kirkpatrick lava flows of the Ferrar Group. The lower stratigraphic unit (Section Peak Formation) is characterised by braided river-type quartzose sandstone deposits with intercalations of shale and coal occurring at the top. It is overlain by a homogeneous unit of reworked tuffs composed of fine-grained silicic shards, quartz and feldspar (new name: "Shafer Peak Formation"). These deposits can be correlated with parts of the Hanson Formation in the Central Transantarctic Mountains and require a distal yet unknown source of massive silicic volcanism. Clastic products of mafic volcanic eruptions, formerly described as a separate stratigraphic formation (Exposure Hill Formation), occur within local diatreme structures as well as intercalated at various stratigraphic levels within the sedimentary succession. These dominantly hydroclastic eruptions are the first subaerial expression of Ferrar magmatism. The initial Kirkpatrick lavas/pillow lavas were generated from local eruptive centres and again may be overlain by thin sediments, which are covered by the thick plateau lava succession known throughout the Transantarctic Mountain Range. Citation: Schöner, R., L. Viereck-Goette, J. Schneider and B. Bomfleur (2007), Triassic-Jurassic sediments and multiple volcanic events in North Victoria Land, Antarctica: A revised stratigraphic model, in Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES, edited by A.K. Cooper and C.R. Raymond et al., USGS Open-File Report 2007-1047, Short Research Paper 102, 5 p.; doi:10.3133/of2007-1047.srp102 Introduction The Ferrar Province in Antarctica is one of the large igneous provinces that was related to the break-up of the supercontinent Gondwana during the Mesozoic. In North Victoria Land (NVL), South Victoria Land (SVL), and the Central Transantarctic Mountains (CTM), Ferrar Province related igneous activity culminated in the effusion of the Early Jurassic Kirkpatrick plateau lava flows, developing a thickness of up to ~1000 m. This volcanic succession overlies ~300 m thick continental siliciclastic and volcaniclastic sediments, which are the focus of this paper. Previous investigations have shown that the Kirkpatrick lava flows are pre-dated by mafic volcaniclastic breccias and tuff breccias in the CTM (Prebble Formation; e.g., Barrett et al., 1986; Elliot, 2000), in SVL (Mawson Formation; e.g., Ballance and Watters, 1971; McClintock and White, 2006) and in NVL (Exposure Hill Formation; e.g., Elliot et al., 1986). Only in the CTM these volcaniclastic breccias are underlain by volcaniclastics of the Hanson Formation, a silicic tuffaceous unit thought to be Early Jurassic in age (Elliot, 1996). Potential correlative silicic tuffaceous sand- /siltstones are also known from SVL and NVL where they form megaclasts in the deposits of the Mawson and Exposure Hill Formation (Elliot et al., 1986; Elliot and Hanson, 2001). These rocks are underlain by quartzose sandstones of the Victoria Group (Beacon Supergroup) in the entire Transantarctic Mountains (e.g., Collinson et al., 1994). The quartzose sandstone unit in NVL is referred to as Section Peak Formation and interpreted as braided river deposits of Middle to Late Triassic (e.g., Collinson et al., 1986; Tessensohn and Mädler, 1987) or even Early Jurassic age (e.g., Norris, 1965; Pertusati et al., 2006). Although the contacts between siliciclastic rocks of the Victoria Group and the overlying volcaniclastic units appear to be concordant, e.g. in the Beardmore Glacier region, CTM (Elliot, 2000), the true contact relationships are often uncertain. In SVL, volcaniclastic deposits that had previously been described as lahars filling up palaeotopography (Ballance and Watters, 1971; Elliot and Hanson, 2001) have recently been re-interpreted as components of vent complexes and magmatically- generated collapse structures (White and McClintock, 2001; Elliot et al., 2006). In NVL, the Exposure Hill Formation is regarded as a separate stratigraphic unit on top of the siliciclastic sequence (Elliot et al., 1986; Elliot et al., 2006), but the contacts were not yet investigated systematically. Based on new field investigations during the 9th German North Victoria Land Expedition (GANOVEX IX, 2005/2006), we describe here the contact relationships of siliciclastic and volcaniclastic rocks underlying the Kirkpatrick lava flows, and suggest a revised model for the Triassic to Early Jurassic stratigraphy of NVL. The Triassic to Early Jurassic succession in North Victoria Land 28 representative outcrops of the Triassic to Early Jurassic sedimentary succession in southern NVL were measured in detail (Fig. 1). The base of this succession is exposed at several localities along the edge of the polar plateau as well as at Stewart Heights and Vulcan Hills. The top is exposed in the Deep Freeze Range and in the