Discriminating between subglacial and proglacial lake sediments: an example from the Danischer Wohld Peninsula, northern Germany

作者：Livingstone Stephen J^*; Piotrowski Jan A; Bateman Mark D; Ely Jeremy C; Clark Chris D

来源：Quaternary Science Reviews, 2015, 112: 86-108.

DOI：10.1016/j.quascirev.2015.01.030

• Subglacial lake
• Proglacial lake
• Ice Sheet
• Sedimentology
• Optically Stimulated Luminescence dating
• Northern Germany

Subglacial lakes are common features of contemporary ice masses. However, they are rarely identified in the geological record. This is due to the difficulty in discriminating between subglacial and proglacial lake sediments; a proglacial origin is typically preferred as the 'simplest' explanation. We hypothesise that numerous deposits currently interpreted to record proglacial lake sedimentation may actually have a subglacial origin. Here we try and find ways of distinguishing proglacial from subglacial lake sediments by investigating three sites along the Danischer Wohld Peninsula, northern Germany, which have been interpreted to record both proglacial and subglacial sedimentation. We identify two major phases of ice activity and associated lake formation during the Late Weichselian glaciation. (I) Proglacial lake formation at similar to 23 ka in front of the advancing Baltic Ice Stream. This lake was subsequently overridden and the sediments glaciotectonised as ice continued to advance to its maximum extent. (2) Retreat of ice back into the Baltic Basin at similar to 19 ka and formation of a proglacial lake that persisted for similar to 4 ka. We suggest that subglacial lake activity may have occurred at two of the sites between 23 and 19 ka. This is based on the presence of aggrading sediment deposits characterised by stratified/laminated diamictons and interbedded tabular to channelized sorted sediments, the juxtaposition of relatively undeformed waterlain sediment and subglacial till, absence of glaciotectonic thrusting and folding or of fining/coarsening successions and the geomorphic association with tunnel valleys to the south of the study area. The style of sedimentation and deformation provided the greatest insight into the discrimination of proglacially vs subglacially deposited glaciolacustrine sediments. The luminescence signal palaeodose distributions also offers a potentially powerful means of fingerprinting sediment transport pathways of young glacial systems.

• 出版日期2015-3-15