Cirque infills in the Khibiny Mountains, Kola Peninsula, Russia — palaeoglaciological interpretations and modern analogues in East Antarctica

Abstract

We report here on cirque infills mapped in the Khibiny Mountains, Kola Peninsula, Russia. Cirque infills are morainic deposits located near the headwalls of valleys and cirques. Their location and shape, often with concave margins towards the valley side, indicate that they were deposited by ice flowing up-valley, into the mountains, rather than by local glaciers. We suggest that they formed during the last deglaciation, when Khibiny was a nunatak and Fennoscandian ice sheet lobes extended into valleys and cirques of the massif. The formation of cirque infills is probably more related to ice sheet dynamic factors, occurring when the ice margin retreated from the cirques, than to climate-driven interruption in the ice-marginal retreat. Glacial conditions similar to those prevalent when the Khibiny cirque infills were formed, occur today in Antarctica where the ice sheets engulf nunatak ranges. In Heimefrontfjella, Antarctica, the formation of supraglacial moraines at the head of cirques are linked to blue-ice conditions, indicating locally low accumulation rates, a dry continental climate and sublimation dominated ablation. We suggest that these Antarctic moraines are modern analogues of cirque infills on the Kola Peninsula, and possibly, that the cirque infills may be used as palaeoenvironmental indicators.

Comments on Jansson, K.N. and Glasser, N.F. (2008) “Modification of peripheral mountain ranges by former ice sheets: The Brecon Beacons, southern UK,” Geomorphology 97, 178–189

“…However, Jansson and Glasser raised the possibility that pronounced, well-formed ridges in the two cirques referred to above (namely Fan Hir and Cwm Llwch) were formed by a recessional stage of the last ice sheet rather than by small Younger Dryas Stadial age glaciers. This follows recent suggestions of such an origin in, for example, Antarctica, Sweden, and Russia (Hättestrand and Johansen, 2005;Heyman and Hättestrand, 2006;Hättestrand et al, 2008). We categorically disagree with this interpretation.…”

“…2B); (v) no erratics were found by Shakesby and Matthews (1993), as would be common if formed by an ice sheet moving across the area (cf. Hättestrand et al, 2008); (vi) it increases in size from the upslope (northern) to downslope (southern) end of the escarpment as would be expected for glacier flow with components of movement both away from the headwall and downslope to the south (cf. Cwm Crew; Fig.…”

“…2A); (vii) two small distinct depositional ridges are aligned obliquely across the gap between the headwall and moraine, which can be explained by formation by minor stillstands during ice wastage at the end of the Younger Dryas Stadial; (viii) it is separated from the headwall by a distinct small valley across which one would expect any ice sheet margin to have extended to leave the moraine banked against the headwall (cf. Hättestrand et al, 2008); and (ix) there is a fan of outwash deposits to the south beyond the gorge that cuts through the southern end of the moraine, which is consistent in scale and position with glaciofluvial drainage from a cirque glacier having occupied the gap between the headwall and moraine ridge. Outwash deposits do not occur elsewhere in the vicinity of the moraine.…”

Evolution of a Lateglacial mountain icecap in northern Scotland

“…Our interpretation is that these mounds were originally deposited by eastward ice cap retreat and thinning (see below), allowing sediment to accumulate between the ice margin and reverse slope, prior to subsequent ice cap thickening, overriding and streamlining. Hättestrand et al (2008) have reported morphologically similar features, termed 'cirque infills' on the Kola Peninsula in Russia. Abundant sources for the debris would have existed during ice cap thinning and retreat, including: rockfall, fluvial transport from the upper valley, and debris flows / fluvial transport from valley sides and ice margin.…”

Controls on Rockfall-Talus Process-Response Systems, Kananaskis, Canadian Rockies

“…Following deglaciation, mountain landscapes continue to be modified by weathering and erosion (Ballantyne, 2002;Hattestrand et al, 2008). It is important to understand these landscape processes because they may modify the altitudinal range of drainage basins and reduce the gradient of mountainous terrain (Barr & Spagnolo, 2015).…”