moraines

till

glacial erratics

esker

kame terrace

outwash terraces

Glacial stratigraphy

On the main tools for reconstructing the glacial history of an area is to examine the local stratigraphic record. Tills are firm indicators of the former presence of glacier ice and the their fabrics and erratic content provide information about the direction of former ice movement. Where tills are interbedded with other sediments, such as meltwater or periglacial deposits then a sequence of events can be built up.

In the Cairngorms, the possibilities for the development of complex stratigraphy has been greatly reduced by the erosive effects of successive ice masses. The latest glaciers tend to erode the loose sediment deposited by earlier ice masses and meltwater. Nonetheless useful information can be provided even when only two tills are superposed, as shown in the example below.

 

Till sequence on the eastern flank of Strath Nethy at around 730 m. The thin layer of granite blocks on the surface rests on a till containing an abundance of metamorphic debris. The stratigraphy suggests that a final flow of ice from Strath Nethy was preceded by ice moving across the mouth of Strath Nethy from Strathspey. Interestingly, this picture does not fit neatly with published interpretation of the glacial history of this area, where the final movement is from Strathspey (Brazier et al., 1998). Does the lower till precede this period?