Shape development of sandstone cobbles associated with the Säkylä-Mellilä esker, southwest Finland

Authors

  • Veijo Kaitanen Department of Geography, University of Turku
  • Olli Ström Department of Geography, University of Turku

Abstract

Sandstone cobble morphology and lithological composition of till, esker and beach material were studied, including about 22 000 morphometric measurements on stones in the 16 ... 128 min size range and about 11000 lithologic identifications on stones in the 4 ... 128 mm size range.

Glacial transportation did not lead to intensive fracturing of the material which evidently originated from the sources nearby, and from relatively unweathered bedrock. Glaciofluvial processes, on the contrary, were mark­edly more powerful, and brought about more radical changes in shape, and strong increase in roundness. During glaciofluvial transportation the mate­rial travelled 6 ... 10 km further, and at the same time the mixing of material was thorough.

Shape, as definable in terms of symmetry, but also as measured in terms of axial ratio, was revealed as very persistent. Where change in shape did occur, it usually was a reinforcement of the original shape. Ideally this became apparent under beach processes on the cobbles of 32 ... 64 mm size class.

Not even the most delicate indices can provide a detailed enough picture of the complex changes undergone by stones of a given lithological composi­tion becoming subject to a series of processes, as the intensity and duration of energy flows in the processes vary extremely widely under natural condi­tions, and many an apparently well‑defined picture becomes complicated by the countervailing effect of mechanisms in the same process.

Section
Research Papers

Published

1978-01-01

How to Cite

Kaitanen, V., & Ström, O. (1978). Shape development of sandstone cobbles associated with the Säkylä-Mellilä esker, southwest Finland. Fennia - International Journal of Geography, 155(1). Retrieved from https://fennia.journal.fi/article/view/9563