The outcrops of Devonian terrigenous sedimentary rock on Ruhnu Island

The Ruhnu Outcrop, also known as the Flisbacka Steep, is the steep on Ruhnu’s east and north-east coast; it has a total length of 2.5 km, and a height of 5.5 m. The length of the bedrock sandstone ridge beneath the Quaternary sediments is about 350 m, and the height of the outcrop 2.3 m. On the ridge, there are outcrops of the Mid-Devonian Narva stratum’s (the upper part of the stratum) terrigenous sediments. These sediments have been the source material for formation of sand deposits. Exposed siltstones, clean and marl clays, and sandstones can be found. In the latter, fossilised fish remains have been found. In the more northern outcrops, marl dolomite can also be found.

The outcrops of Devonian terrigenous sedimentary rock on Ruhnu Island are the only ones in Saare County, and this is the only location in Estonia where they are abraded by the sea.

The Ruhnu Outcrop has been included in the data base of the volume Eesti ürglooduse raamat (Estonian Book of Primeval Nature), and is included in the Ruhnu limited conservation area.

Created in 2013