Testing the groove-ploughing theory for mega-scale glacial lineaton (MSGL) formation, using a large dataset of their morphology

Abstract

Subglacial bedforms provide an important insight into the nature of the processes operating at the ice-bed interface. In particular, the well-established link between mega-scale glacial lineations (MSGLs) and ice streams allows for indirect examination of the processes controlling the flow of ice streams, using observations of the morphology of features from palaeo-ice stream beds. Determining whether the existing theories of MSGL formation, in particular the groove-ploughing theory, can produce landforms with the morphology observed from palaeo-ice stream beds, is likely to have a significant impact on the understanding of the mechanisms that control the flow of ice streams.
A number of theories for MSGL formation have been proposed in the literature. There have, however, been relatively few attempts to falsify these theories. This is partially due to the limited amount of observational data, regarding MSGL morphology and internal composition. In particular, the groove-ploughing theory for MSGL formation provides a number of predictions which can be tested by examining the morphology of lineation populations. This work constitutes the first extensive test of the groove-ploughing theory, using a large dataset of MSGL morphology from a number of different palaeo-ice stream beds.
The objective of this work is to digitise a large sample of lineations, from three different palaeo-ice stream beds, in order to test the predictions of the groove-ploughing theory. It is necessary to identify the specific predictions that can realistically be tested using lineation morphology, and to devise measures that provide quantifiable tests of these predictions. Using the measures devised to test these predictions, along with close qualitative observation of other features of the palaeo-ice stream beds studied, it is found that the morphology of the lineations studied do not generally conform to the predictions of the groove-ploughing theory.