DISTRIBUTION, MORPHOMETRY AND GENESIS OF DRUMLINS AND STREAMLINED TILL PATCHES IN SOUTHERN SWEDEN

Abstract

Research on streamlined landforms offers valuable insights into the evolution of glaciated landscapes and the characteristics of the ice sheets responsible for their formation. Despite the significance of these bedforms, the exact processes responsible for their subglacial formation remain a subject of debate. The goal with this master thesis is to identify and analyze drumlins and streamlined till patches in southern Sweden to enhance the understanding of their distribution, morphometrics and genesis. To answer the set goals, this study was carried out through GIS-, field-, and lab work. A total of 1187 drumlins and streamlined till patches were identified in this study, and they are mainly situated at elevated and/or eroded surface forms of the bedrock. Length, width, elongation ratio, area, spacing between features, height, and orientation were measured in this study for all the landforms, as well as drumlins and streamlined till patches separately. The length, width, and height of the drumlins are generally larger than other drumlins identified within Sweden and elsewhere. Only a few parameters show strong correlations with each other, namely length vs width, length vs area, and width vs area. Drilling and excavation data showed 78 features with diamicton all the way down to the bedrock. Nine landforms were identified with sorted sediment under a cover of diamicton, one from field work and eight from compilation of previous drillings and excavations. Sand was predominantly found here. The sorted sediment is interpreted to predate the overlying diamicton as it may have been deposited during a previous glaciation. 1083 of the mapped drumlins and streamlined till patches were furthermore found with bedrock knobs. This suggests that presence of bedrock had a significant role in the landform formation. Undulated hilly terrain is a key aspect in the formation of mapped drumlins and streamlined till patches, as it may control the accumulation and distribution of material. Multiple studies propose that drumlins can be classified according to three primary processes shaping their formation: erosion, deposition and deformation. The first two have been considered in this study. Evidence of erosion, such as the presence of older sub-till sediment, margins altered by meltwater corridors, the shielding effect of bedrock knobs, and the preservation of sediment, highlights potential mechanisms contributing to the formation of drumlins and streamlined till patches. Evidence of deposition are indicated through the presence of till comprising the mapped landforms. Presence of sorted sediment could also have induced the deposition of till, resulting in the emplacement of till on top of the sorted sediment.