Orvinfjella

Orvinfjella
	Southern Drygalski Mountains, view to the NW
location	Queen Maud Land , East Antarctica
part of	Fimbulheimen
Coordinates	71 ° 55 ′ S , 9 ° 0 ′ E Coordinates: 71 ° 55 ′ S , 9 ° 0 ′ E

The Orvinfjella is a mountain group in Antarctica , which lies in the Dronning Maud Land claimed by Norway . In January 1939, the mountain group was discovered during flights of the German Antarctic Expedition 1938/39 and documented in aerial photographs , but only individual parts of the mountain range were named by the German expedition. As part of the Norwegian Antarctic Expedition 1956–1960, the area was mapped on a scale of 1: 250,000 and named after the geologist Anders Kristian Orvin (1889–1980, head of the Norsk Polar Institute from 1957 to 1960).

Geography and geology

The mountain group comprises a group of north-south oriented, about 15 to 35 kilometers long mountain ranges, which protrude about 150 kilometers in the interior of the Antarctic from the inland ice . These are from west to east:

The mountain group is separated from the neighboring mountain groups by wide glaciers . In the west, the Djupedalen at 7 ° east forms the border between the Filchner Mountains and the Mühlig-Hofmann Mountains , the Somoveken glacier at around 11 ° east separates the Orvinfjella from the Wohlthat massif . The individual mountains are separated from each other by smaller glaciers, which unite on the glaciated foreland between the mountains and the coast known as the Hellehallet .

The oldest rocks are highly metamorphic , multiply folded gneisses and amphibolites , the parent rocks of which are volcanics and plutonites of an island arc with a Mesoproterozoic age. At the turn of the Mesoproterozoic / Neoproterozoic , these rocks were deformed and metamorphically shaped for the first time when the island arc collided with the Grunehogna craton . Melts with a granitic and tonal composition penetrated and solidified in the form of thin corridors. The rocks underwent a further deformation when the West and East Gondwana collided approx. 540 mya ago , which resulted in the fold structure that is now oriented towards east and west . In the northern parts of Drygalski Mountains, the Holtedahlfjella and Conrad mountains are immediately after the formation of mountains on several square kilometers syenite - and alkali granite - Plutone penetrated and solidifies. The mountains have been subject to erosion since the Ordovician . During this period there was extensive glaciation in the Permian and since the beginning of the current glacial period.