Terminal stages of the evolution of sheet and mountain glaciations in Khibiny

Abstract

The purpose of this work is to reconstruct terminal stages of the evolution of sheet and mountain glaciations in the Khibiny mountainous massif. We investigated a vast area of nepheline syenites of the Khibiny pluton in the southern Khibiny Massif. This area is characterized by an abundance of glacial cirques and the existence of mountain glaciations [1, 2]. We revealed here typical structures of the marginal belt of the Scandinavian glacier as dump and push moraine ridges [3] (Fig. 1). The northern part of the area includes deposits of mountain glaciers with a specific composition of clastic material. Judging from the petrographic composition of the pebble fraction and the mineral composition of sand and silt, the clastic material is almost entirely represented by products of destruction of nepheline syenites of the Khibiny intrusive massif. Mountain glaciers and their meltwaters include the following structures: (i) end moraines damming valleys of the Poachvumjok and Vudjavrjok rivers; (ii) ridges resembling De Geer moraines; (iii) glaciofluvial deltas formed by meltwater running southward and located in valleys of the Poachvumjok and Vudjavrjok rivers behind end moraines; (iv) periglacial lake terraces developed at an altitude of about 500 m in the Poachvumjok river valley; and (v) a small sandur with an even surface complicated by “pocks” of the Malyi Vudjavr and Kupal’noe lakes obviously indicating the filling of lake depressions with dead ice during the sandur formation. The southern part of the study area includes sheet glaciation deposits that are developed represented by dump and push moraine ridges, as well as a thin cover