Re-evaluating the sub-Caledonian erosion surface at the border of the Caledonides in Enontekiö Lapland, north-western Finland

Abstract

The sub‑Caledonian erosion surface in the northwesternmost tip of Finland lies almost horizontal under the Finnish Caledonides. In its most easterly part, east of the Valtijoki River, the erosion surface was assumed to be located in an elevated position. Recent mapping shows the elevation to be an illusion created mainly by the absence of the very steeply jointed Kalak Nappe schists that elsewhere cap the lower Caledonian units. The rock now exposed is a quartzite that has yielded to erosion, so causing the more com­mon, undulating topography. The pre‑Caledonian basement had, however, been subject to fracturing that developed into broader zones of erosion such as the Valtijoki River valley or, as single fractures, was healed by diabase intrusions which seem to have fortified the foundations of some present‑day fells. Extrapolating the erosion surface to SE necessitates a greater evening of its inclination.