The Gondwana successions in Antarctica unconformably overlain the Ross Orogen terranes and are widespread throughout the whole Transantarctic Mountains. They are mainly represented by the siliciclastic Devonian-Jurassic Beacon Supergroup and the Jurassic Ferrar Dolerite-Kirkpatrick Basalt. In Northern Victoria Land (NVL), they occur with variable age and thickness, ranging from few tens of meters to 300 m. The outcrops are scattered in two wide regions including the lowerRennick Glacier (studied in the 80s by USA-NZ-AUS and german teams) and the lower Priestley and Campbell glaciers studied in the 90s by italian teams. According to many authors, the clastic successions of the NVL, called Takrouna Fm. (Permian) in the northernmostoutcrops and Section Peak Fm. (Triassic-?Jurassic) inthe southernmostones, represent the siliciclastic, mainly cross-bedded sandstone infilling of alluvial Permo-Triassic basin systems, and corresponding to the prolongation to the north of the wider basin system, located in Southern Victoria Land, of the Beacon Supergroup. It is worth to note that the age of the latter formation is not well constrained, because, despite the presence of Triassic paleoflora and trace fossils, the relationships with the overlying middle Jurassic lava beds, dykes and sills are not well defined. These formations show a general flat-bedding attitude, and they unconformably overlain the basement formed of metamorphic and intrusive rocks of the Wilson Terrane, through a regional erosional surface called “sub-Beacon Peneplain”. For this overview, based on available previous geological maps and on a new survey performed during the 2012/13 Italian Antarcticexpedition, we have investigated many of the NVL Beacon-like outcrops, which are greatly scattered, due to their low-thickness and ice cover. These factors make difficulties for a high-resolution bed-correlation, but a stratigraphic-sedimentological architecture frame can be tentatively defined. To this aim, sedimentological facies and petrographical analyses have been preliminary performed and will be developed in the next steps of the research. In the Rennick Glacier area, the base of the siliciclastic succession may consist ofa 20-50 m thick diamictite-fluvioglacial horizon. The clastic successions comprise a wide spectrum of coarse sedimentary facies, with dominant pebbly to coarse sandstones with trough or planar cross-bedding, and subordinate massive microconglomerates, massive and normal graded sandstones, carbonaceous mudstones with fossil leave impressions and trunk remains, coal deposits. The sandstone composition, reveals high maturity, containing mainly quartz and feldspar clasts, with minor lithic fragments, ranging from quartzarenite to subarkose to arkose, whereas the upper portion of the westernmore successions show significant volcanic clastic content, so to define volcanic-bearing lithic arkoses. Palaeocurrent data show a north to northwest wide dispersion. The depositional system agrees with a wide alluvial plain characterized by large and deep rivers with braided to meander style, compatible with the sandy-braided model (similar to the deep perennial braided “S. Saskatchewan type” of Miall), forming compound bars with sandy bedforms and downstream accretion macroforms, infilling a plain close to a high to moderate morphological gradient area. The thickness differences between southern and northern sectors of the NVL, allow to define a basin variability and splitting, due to the tectonic rifting processes, starting during Triassic with the formation of the Rennick Glacier “graben” and developing in the Jurassic with the volcanic activity.

(2013). Overview on the stratigraphic and sedimentological features of the Permian-Mesozoic continental successions in Northern Victoria Land (Transantarctic Mountains, Antarctica). In Abstract Volume of the 30th IAS Meeting. Manchester.

Overview on the stratigraphic and sedimentological features of the Permian-Mesozoic continental successions in Northern Victoria Land (Transantarctic Mountains, Antarctica)

Cornamusini, G.;Talarico, F. M.
2013

Abstract

The Gondwana successions in Antarctica unconformably overlain the Ross Orogen terranes and are widespread throughout the whole Transantarctic Mountains. They are mainly represented by the siliciclastic Devonian-Jurassic Beacon Supergroup and the Jurassic Ferrar Dolerite-Kirkpatrick Basalt. In Northern Victoria Land (NVL), they occur with variable age and thickness, ranging from few tens of meters to 300 m. The outcrops are scattered in two wide regions including the lowerRennick Glacier (studied in the 80s by USA-NZ-AUS and german teams) and the lower Priestley and Campbell glaciers studied in the 90s by italian teams. According to many authors, the clastic successions of the NVL, called Takrouna Fm. (Permian) in the northernmostoutcrops and Section Peak Fm. (Triassic-?Jurassic) inthe southernmostones, represent the siliciclastic, mainly cross-bedded sandstone infilling of alluvial Permo-Triassic basin systems, and corresponding to the prolongation to the north of the wider basin system, located in Southern Victoria Land, of the Beacon Supergroup. It is worth to note that the age of the latter formation is not well constrained, because, despite the presence of Triassic paleoflora and trace fossils, the relationships with the overlying middle Jurassic lava beds, dykes and sills are not well defined. These formations show a general flat-bedding attitude, and they unconformably overlain the basement formed of metamorphic and intrusive rocks of the Wilson Terrane, through a regional erosional surface called “sub-Beacon Peneplain”. For this overview, based on available previous geological maps and on a new survey performed during the 2012/13 Italian Antarcticexpedition, we have investigated many of the NVL Beacon-like outcrops, which are greatly scattered, due to their low-thickness and ice cover. These factors make difficulties for a high-resolution bed-correlation, but a stratigraphic-sedimentological architecture frame can be tentatively defined. To this aim, sedimentological facies and petrographical analyses have been preliminary performed and will be developed in the next steps of the research. In the Rennick Glacier area, the base of the siliciclastic succession may consist ofa 20-50 m thick diamictite-fluvioglacial horizon. The clastic successions comprise a wide spectrum of coarse sedimentary facies, with dominant pebbly to coarse sandstones with trough or planar cross-bedding, and subordinate massive microconglomerates, massive and normal graded sandstones, carbonaceous mudstones with fossil leave impressions and trunk remains, coal deposits. The sandstone composition, reveals high maturity, containing mainly quartz and feldspar clasts, with minor lithic fragments, ranging from quartzarenite to subarkose to arkose, whereas the upper portion of the westernmore successions show significant volcanic clastic content, so to define volcanic-bearing lithic arkoses. Palaeocurrent data show a north to northwest wide dispersion. The depositional system agrees with a wide alluvial plain characterized by large and deep rivers with braided to meander style, compatible with the sandy-braided model (similar to the deep perennial braided “S. Saskatchewan type” of Miall), forming compound bars with sandy bedforms and downstream accretion macroforms, infilling a plain close to a high to moderate morphological gradient area. The thickness differences between southern and northern sectors of the NVL, allow to define a basin variability and splitting, due to the tectonic rifting processes, starting during Triassic with the formation of the Rennick Glacier “graben” and developing in the Jurassic with the volcanic activity.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11365/709232
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