Electrical-sedimentary anisotropy of Rogen moraine, Lake Rogen area, Sweden

Abstract

The electrical-sedimentary and morphological anisotropy of Rogen moraine was studied with aerial photographs and azimuthal measurements of electrical conductivity (σ a) in the Lake Rogen area, Härjedalen, Sweden. The Rogen ridges are fluted on their surfaces and exhibit down-ice horn-features linked to active transverse-to-ice and subglacial genesis. The maximum σ a-anisotropy of sediments in the cores of the Rogen ridges was parallel to the orientation of the ridge trends. The core was mantled with sediments exhibiting σ a-anisotropy parallel-to-iceflow, yet the σ a-anisotropy of surface sediments reflects slope reworking. On the basis of morpho-sedimentary anisotropy we contend that Rogen moraine is polygenetic in origin and exhibits both transverse-to-ice (older) and parallel-to-ice (younger) electrical-sedimentary stratigraphy. Due to the lack of dating evidence it remains unresolved whether the Rogen moraine was formed during one or several Weichselian glacial events. Polygenetic origin may apply only to the type of area found on the northeast side of Lake Rogen. On the southwestern side of Lake Rogen, the ribbed ridge morphology is highly diverse, and is difficult to explain by the polygenetic model as well as monogenetic concepts of frozen-bed extension and bed ribbing instability.