The Permo-Carboniferous of North Victoria Land, Antarctica: continental despositional systems and paleo-environmental evolution of a high-latitude Gondwana basin
Zusammenfassung der Projektergebnisse
During the late Paleozoic a series of sedimentary basins occupied the eastern margin of Gondwana, which is considered as long-lasting subduction-related plate boundary. Nature, evolution and provenance of some of these basins, for example of the Permian Victoria Basin in the Ross Sea sector of East Antarctica, are still poorly understood. The Permian Takrouna Formation in northern Victoria Land represents the fossil record of the northern part of this basin system, exposed within an outcrop belt with an extension of 125 × 160 km. The Takrouna Formation is an up to 300 m thick succession of siliciclastic deposits that documents the onset of sedimentation after a long period of erosion and the Late Carboniferous to Early Permian glaciation of Gondwana. The Takrouna Formation grades from unnamed heterogeneous basal deposits including abundant matrix-supported conglomerates, or unconformably overlies pre-Devonian basement, which consists of three major fault-bounded terranes. The Takrouna Formation includes conglomerates, sandstones, carbonaceous fine-grained rocks and coal that were deposited in a braided river system, draining towards Tasmania. Fluvial architecture at the base of the Takrouna Formation demonstrates multistory stacked channel bodies with a sheet-like geometry. It gradually changes upwards forming well-defined channel-fill deposits associated with units of finer-grained deposits, indicating a decrease in transport capacity. A coarse-grained, pebbly sandstone facies was recognized in all sections and allows, together with distinct architectural facies elements, a lithostratigraphic correlation across the basin. Above the central sheet-like sandstone unit ripple-laminated sandstone was deposited on a large braid-plain, where local topography was largely leveled out. Stressing bounding-surface hierarchies and architectural analysis, the control on channel-belt avulsion and migration was related to autogenic processes. In contrast, large-scale, vertical grain size trends observed across the basin are considered to represent allogenic signals, related to either tectonic or climatic processes. The observed regional fining of grain-sizes towards the western part of the study area, the facies trends and paleocurrent measurements indicate the existence of an eastern basin margin and an axial drainage system in the western part of the study area, perpendicular to this basin margin. The sandstones of the Takrouna Formation are litharenites, sublitharenites and rarely lithic subarkoses. All studied localities show only minor differences in their light mineral composition, but are distinct in their heavy mineral assemblage. U-Pb data of detrital zircon enable the distinction of mainly Archean to Proterozoic, Grenville, Pan-Gondwana and a 450-300 Ma age populations. Sandstones from the eastern mountain contain material derived from the Bowers and Robertson Bay Terrane metasedimentary units at the eastern basin margin. The heavy mineral assemblages in the western part of the study area together with the detrital zircon age spectra suggest mainly reworking of Wilson Terrane basement. Because the heavy mineral composition in the lower part of the succession is different from locality to locality, but lithofacies assemblages are similar, a major input of material from distinct local sources, filling a pre-existing relief, can be assumed for the early stages of sedimentation. A vertical trend is evident from the successions of the central mountain ranges, showing the income of a garnet source in the upper part of the sections. An unknown, garnet-bearing low- to medium-grade metasedimentary basement source is proposed to occur to the east of the Robertson Bay Terrane to explain the abundance of the observed garnet varieties in the eastern and central part of the study area. Most other heavy minerals can be related to sources equivalent to the basement in, or in the vicinity of, northern Victoria Land. All data indicate a shift from local sources in the lower part to a mixed provenance of distal and proximal sources in the upper part of the Takrouna Formation. This is interpreted as the establishment of a major drainage system that evolved on a large-scale braid-plain subsequently to the infill of local paleotopography. Considering heavy mineral abundances and lithofacies associations, the Permian Weller Coal Measures of southern Victoria Land and the Takrouna Formation in northern Victoria Land were rather deposited in two separate sub-basins than in a connected drainage system within one basin, but probably had similar source lithologies. Lithofacies patterns and sedimentary architecture of the Takrouna Formation point to an intracontinental basin, where slow subsidence was induced by dynamic loading in the mantle. A forebulge was possibly located to the east of the present-day northern Victoria Land. This forebulge is proposed as the source of the abundant garnet variety of the Takrouna Formation, which requires a yet unknown low- to mediumgrade metasedimentary source area.
Projektbezogene Publikationen (Auswahl)
- (2010): The Permian Beacon Supergroup of North Victoria Land, Antarctica: Evolution of a fluvial system. 24. Internationale Polartagung, Obergurgl/Österreich, 05.09.-09.09.2010
John, N., Schöner, R. & Gaupp, R.
- (2011): A heavy mineral-based provenance study of the Permian Takrouna Formation, Antarctica. The Geological Society of London: Sediment Provenace Studies in Hydrocarbon Exploration & Production, London/UK, 5.-7.12.2011
John, N., Schöner, R. & Gaupp, R.
- (2011): Sedimentary architecture and provenance of the Permian Beacon Supergroup of North Victoria Land, Antarctica: Implications for the correlation of a fluvial system. 11th International Symposium on Antarctic Earth Sciences, Edinburgh/UK, 10.07.-16.07.2011
John, N., Schöner, R. & Gaupp, R.
- (2012): Eine Schwermineral-Studie der Takrouna Formation, Nord- Viktoria-Land: Mögliche Liefergebiete und Geometrie des permischen Sedimentbeckens. 35.Treffen des Arbeitskreises „Geologie und Geophysik der Polargebiete“ der Deutschen Gesellschaft für Polarforschung
John, N., Schöner, R. & Gaupp, R.
- (2012): The depositional evolution and provenance of a fluvial post-glacial basin: the Takrouna Formation, Antarctica. GV and SEDIMENT meeting 2012, Hamburg, 23.09-28.09.2012
John, N., Schöner, R., & Gaupp, R.
- (2013): Provenance of the Permian Takrouna Formation, Antarctica - Implications on basin geometry and paleogeography. 25. Internationale Polartagung, Hamburg, 17.03.-22.03.2013
John, N., Schöner, R., Gerdes, A. & Gaupp, R.
- Sedimentological field investigations on Permian deposits (Beacon Supergroup) in Northern Victoria Land, Antarctica. Polarforschung 84 (1), 49–58, 2014
Schöner, R. & John, N.
- Sedimentology and composition of the Takrouna Formation, northern Victoria Land, Antarctic : Provenance and depositional evolution of a Permian Gondwana basin. - PhD Thesis, Univ. Jena, 256 pp., 2014
John, N.
