The influence of climate and tectonics on uplift and denudation of the Terra Nova Bay Region (Transantarktisches Gebirge)
Zusammenfassung der Projektergebnisse
The Transantarctic Mountains (TAM) are a 3,500 km long and up to 5,000 m high mountain chain that was supposed to have been formed in discrete uplift episodes during the Early Cretaceous, Late Cretaceous, and Cenozoic. However, stratigraphic and thermochronological crossover age data and various geological inconsistencies challenge this traditional concept. Therefore, the project applied low-temperature thermochronological methods supplemented by structural 2 investigation and thermal indications on rock samples from the Terra Nova Bay, a ~10,000 km region at the western Ross Sea coast. Apatite fission track and (U-Th-Sm)/He ages between 28±3 and 274±17 Ma and associated proxies from Eisenhower Range, Deep Freeze Range and northern Prince Albert Mountains were, for the fist time in the TAM, thoroughly modelled and considered in the geomorphological context to derive the thermal state of the uppermost crust at various time slices. Main goal of this research was the establishment of a new, realistic exhumation and uplift scenario for the TAM with particular focus on the paleogeographic setting of the region within Gondwana, the development of the continental transform margin between Antarctica and Australia, mode and timing of rifting across the Ross Sea (i.e., the West Antarctic Rift System), uplift mechanism(s) of the TAM, and the influence of climate, tectonics and lithology on exhumation. The results of the grant can be generally divided into methodological and geological aspects. From the methodological point of view, thermal history modelling of vertical profiles demonstrated that FT data obtained by population technique can only help to constrain very rapid cooling processes, and a break in slope in the altitude-age regression does usually not date cooling events. Instead, such a break in slope only provides minimum time constraints for the onset of cooling, and cannot resolve complex thermal histories or substitute thermal history modelling. As a consequence, all proposed thermal histories and exhumation scenarios from the whole TAM qualitatively derived in earlier studies need to be verified by numerical thermal history modelling and cross-checked against geological reality. The consistent thermal history models also have most severe geological implications. Long lasting heating of Jurassic paleosurfaces and volcanic rocks until late Eocene times can only be explained with the formation of a Mesozoic Victoria Basin on the extended continental crust beneath the Antarctic Ross Sea sector and SE Australia. The presently exposed basement of the Terra Nova Bay was buried by an up to 2.5 km thick pile of volcanic and sedimentary rocks. Mid-Jurassic basin formation and subsequent sediment accumulation may have been caused by initial extension of the West Antarctic Rift System at ~180 Ma, with a continuous stable stress field of low E-W extension prevailing until Ross Sea rifting started at ~35 Ma. High Jurassic intrabasinal heatflow with geothermal gradients of 45°–60°C was apparently related to the Ferrar volcanic activity, and decreased to a stable conventional geothermal gradient of 25°–28°C throughout Cretaceous to Eocene times. Exhumation and uplift of the TAM since ~35 Ma occurred in two steps of rapid basin inversion and isostatically triggered basement uplift with intensive glacial incision.
Projektbezogene Publikationen (Auswahl)
-
(2011): Late Ross-orogenic deformation of Granite Harbour Intrusives in the northern Deep Freeze Range, Victoria Land, Antarctica: the Lichen Hills Shear Zone. – Polarforschung, 80, 60-70
Läufer, A.L., Lisker. F. & Phillips, G.
-
(2011): Neogene tectonics in the Edisto and Tucker Inlet region and its correlation with offshore magnetic anomalies north of Cape Adare, northern Victoria Land, Antarctica. – Polarforschung, 80, 111-126
Läufer, A.L., Damaske D. & Lisker, F.
-
(2011): Thermochronological research in northern Victoria Land (Antarctica): a key to the pre-disintegration palaeogeography of Panthalassian Gondwana. – Polarforschung, 80, 100-110
Lisker, F. & Läufer, A.L.
-
(2013): The Cretaceous Victoria Basin between Australia and Antarctica. – Geology, 41, 1044-1046
Lisker, F. & Läufer, A.L.
-
(2013): The Eisenhower Range, Transantarctic Mountains: Evaluation of qualitative interpretation concepts of thermochronological data. – Chemical Geology, 352, 176-187
Prenzel, J., Lisker, F., Balestrieri, M.L., Läufer, A.L. & Spiegel, C.
-
(2014): Burial and exhumation of the Eisenhower Range, Transantarctic Mountains, based on thermochronological, maturity and sediment petrographic constraints. – Tectonophysics, 630, 113- 130
Prenzel, J., Lisker, F., Elsner, M., Schöner, R., Balestrieri, M.L., Läufer, A.L., Berner, U. & Spiegel, C.
-
(2014): Geology of the Millen Thrust System, northern Victoria Land, Antarctica – Polarforschung, 84, 39-47
Phillips, G., Läufer, A. & Piepjohn
-
(2014): Recent thermochronological research in northern Victoria Land, Antarctica. – Polarforschung, 84, 59-66
Lisker, F., Prenzel, J., Läufer, A. & Spiegel, C.
