A weathered diamicton beneath Upper Weichselian sediments at Silvereke, southeastern Sweden

Abstract

An at least 2 m thick, weathered, non‐glacial diamicton, buried beneath a 6 m thick Upper Weichselian glaciogenic sequence at Silvereke in SE Sweden, is composed of variously coloured angular/rhombohedral to rounded clasts set in a red or reddish‐brown matrix of clayey silty sand. The clasts (mainly local metavolcanic rock and Cambrian sandstone) are generally thoroughly weathered and would hardly survive transport, suggesting weathering after deposition. XRD‐analysis of the clay fraction of individual argillized clasts reveals an assemblage dominated by kaolin minerals, probably including halloysite. The matrix has a more complex clay mineralogy, including vermiculite. The petrography and mineralogy as well as the extensive argillization of the diamicton contrast to the composition and texture of the overlying Upper Weichselian till. Apart from small amounts of pollen, mainly Pinus, Betula and NAP, the unit is almost devoid of organic matter. Since most pollen are well‐preserved, they were probably added to the exposed, weathered sediment. The pollen spectrum evidence a Quaternary age. It is suggested that the Silvereke diamicton was deposited between the Pliocene and the beginning of the Eemian Interglacial, and that the Silvereke diamicton‐Upper Weichselian till boundary represents a hiatus, or erosional unconformity, of between 117,000 and some million years.

Olvmo, M., Ronnert, L., Ekman, S.R. & Olsson, S., 1996: A weathered diamicton beneath Upper Weichselian sediments at Silvereke, southeastern Sweden. GFF, Vol. 118 (Pt. 2, June), pp. 65–71. Stockholm. ISSN 1103–5897.

Keywords:

• Diamicton
• Quaternary stratigraphy
• weathering
• kaolin minerals
• SE Sweden