Orvin Mountains
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Southern Drygalskiberge, looking northwest
The Orvinfjella is a mountain range in Antarctica which lies in the claimed of Norway Dronning Maud Land. In January 1939, the mountain range was discovered at the German Antarctic Expedition flights 1938/39, and documented on aerial photographs, but only certain parts of the mountains were named by the German expedition. As part of the Norwegian Antarctic Expedition 1956-1960, the area was mapped at a scale of 1:250,000 and by the geologist Anders Kristian Orvin ( 1889-1980, head of Norsk Polarinstitutt 1957-1960 ) named.
Geography and Geology
The mountain group includes a group of north- south direction, about 15 to 35 km long mountain ranges that protrude about 150 km inland Antarctica from the ice cap. These are from west to east:
- The Filchnerberge
- The Drygalskiberge
- The Holtedahlfjella
- The Short Mountain
- Conrad Mountains
- The Dallmannberge
The mountain range is separated by wide glacier from the adjacent mountain ranges. To the west of Djupedalen forms at 7 ° east longitude, the boundary between the Filchnerbergen and the Mühlig -Hofmann Mountains, the Somovgletscher at about 11 ° east separates the Orvinfjella from Wohlthat solid. The individual mountains are separated from each other smaller glaciers, which unite on the designated as Hellehallet glaciated foothills between the mountains and coast.
The oldest rocks are highly metamorphosed, folded several times gneisses and amphibolites, their parent rocks are volcanic and plutonic rocks of an island arc with mesoproterozoischem age. At the turn Mesoproterozoikum / Neoproterozoic these rocks were in the collision of the island arc with the Grunehogna craton first overprinted deformed and metamorphosed. It melts penetrated with granitic and tonalitischer composition solidified in the form of thin transitions. Another deformation went through the rocks in the collision of West and East Gondwana about 540 mya, with the east-west oriented Faltenbau today was born. In the northern parts of Drygalskiberge, the Holtedahlfjella and the Conrad Mountains syenite and alkali granite plutons are immediately after the orogeny to several square kilometers penetrated and solidifies. Since the Ordovician is subject to the mountain of the ablation. In this period there were in the Permian and since the beginning of the current cold period to extensive glaciation.