NJG84-2-02
2004
The Larajæg’gi outcrop – a large combined Neoproterozoic/Pleistocene roche moutonnée at Karlebotn, Finnmark, North Norway.
84
2
pp. 107-115
82-92394-13-3

The gneiss hillocks , which emerge above the Karlebotn quartzite of the Neoproterozoic Smalfjord Formation in the Karlebotn area, North Norway, have been interpreted as primary, uneven basement relief under the Neoproterozoic cover. A study of the largest gneiss occurrence, the Larajæg’gi outcrop (c. 200 x 350 m), showed these features to be large, inherited Neoproterozoic (Varangerian) roches moutonnées, modified later by Pleistocene glaciation(s).

The western surface of the Larajæg’gi gneiss outcrop is clearly a Pleistocene stoss slope as its smoothly rounded surface inclines up-glacier to the latest Pleistocene ice movement, which was from west to east in the area. However, the foot part of the opposite side of the gneiss outcrop does not show any evidence of being a Pleistocene lee side, but the gneiss surface is smoothly rounded, in part grooved, and has a convexo-concave surface topography with crestal hinge-lines plunging gently to the east, under the Karlebotn quartzite. This is attributed to abrasion caused by the Neoproterozoic ice, which moved from the present east to the present west; i.e. from the opposite direction to that of the latest Pleistocene ice. This interpretation is supported by relics of Neoproterozoic diamictite filling fractures and hollows in the basement gneiss on the Pleistocene stoss side indicating that this side originally represented the rough and hackly Neoproterozoic lee side. The preserved Neoproterozoic features of the Larajæg’gi roche moutonnée support the hypothesis that during the later stage of the first Varangerian glaciation the ice flowed from the present east to the present west.

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