Genesis of the Lammi esker (Sothern Finland)

Abstract

The Lammi esker forms a part of an esker chain stretching NW from the moraines of I Salpausselkä. The described section is about 10 km long. The Lammi esker runs along the axis of a well‑marked trough in the bedrock.

The esker constitutes a chain of poorly‑developed proglacial deltas connected by means of short ridges. The deltas formed in the Baltic Ice Lake at the mouth of crevasses along which glaciofluvial drift was delivered. Each delta registers an ice‑front of strong ablation. During the ice‑front recession the subglacial crevasses were filled up with debris.

Within the described area there are also terminal‑moraine forms which presumably mark the ice‑front during the II Salpausselkä stage. They consist of proximal erratic debris and till overlying glaciofluvial deposits. Glaci­tectonic disturbances of sand formations were found at one place.

During the field work attention was also paid to traces of former shorelines. Cliffs formed during the lowering of the Baltic Ice Lake water‑level (B III) down to the level of the Yoldia Sea (Y I), as well as during later Yoldia stages, Y II and Y IV.