Abstract
ABSTRACTFláajökull is a non-surging outlet glacier draining the south-eastern part of the Vatnajökull, southeast Iceland. Fláajökull was stationary or advanced slightly between 1966 and 1995 and formed a prominent end moraine. Glacial retreat since then has revealed a cluster of 15 drumlins. This study focuses on the morphology and sedimentology of the drumlins. They are 100–600 m long, 40–130 m wide, and have cores of glaciofluvial sediment or till. The drumlins are draped by ~1 m thick, massive subglacial traction till. The glacier forefield is characterized by a number of arcuate and saw-tooth, terminal and recessional moraine ridges, overridden moraines with fluted surfaces, and glaciofluvial outwash. Some of the drumlins extend towards the 1995 end moraine but terminate abruptly at the moraine and are not observed in front of it. This suggests that they were formed sub-marginally during the 1966–1995 terminal position. The sedimentary structure of the drumlins is best explained by the sticky spot model. Dating and dendrochronological analyses of birch logs found on the surface of one of the drumlins indicate that the valley was forested about 2100 calendar year BP, after which the glacier started to reform, possibly due to an abrupt change in climate.
Highlights
Drumlins are important landforms of many Pleistocene landscapes and, they have been extensively studied, the exact nature of their formation is still enigmatic (Menzies, 1979; Patterson and Hooke, 1995; Clark and others, 2009)
The glaciofluvial sediment in the drumlin cores suggests that the drumlins were formed around sticky spots in the substrate where higher resistance to basal sliding, erosion and deformation caused the deposition of the subglacial traction till (Boulton, 1987; Piotrowski and others, 2004; Stokes and others, 2007)
It can be concluded that the drumlins at Fláajökull were formed under ‘normal’ ice velocities like previously reported from for example, Sléttjökull and Sólheimajökull in Iceland rather than under substantially enhanced velocities, as has been suggested for highly elongate Pleistocene drumlins (e.g. Hart, 1999; Stokes and Clark, 1999, 2002; Briner, 2007; Hess and Briner, 2009) and for drumlins formed by surge-type glaciers in Iceland (e.g. Boulton, 1987; Hart, 1995; Waller and others, 2008; Johnson and others, 2010)
Summary
Drumlins are important landforms of many Pleistocene landscapes and, they have been extensively studied, the exact nature of their formation is still enigmatic (Menzies, 1979; Patterson and Hooke, 1995; Clark and others, 2009). Drumlins are usually thought to have formed some distance behind the ice front. This is reflected in ice stream models (Stokes and Clark, 2001), in the active temperate glacial landsystem model by Evans and Twigg (2002), and has been suggested for well-studied drumlin fields, such as the Great Lakes region drumlin fields of North America (Kerr and Eyles, 2007; Maclachlan and Eyles, 2013). Drumlins are not as common in the forefields of modern glaciers as in Pleistocene landscapes. The only modern drumlin field that has been described is at Múlajökull, Central Iceland (Johnson and others, 2010; Jónsson and others, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
