Geological Survey of Finland, Special Paper 46 - arkisto.gsf.fi
Geological Survey of Finland, Special Paper 46 - arkisto.gsf.fi
Geological Survey of Finland, Special Paper 46 - arkisto.gsf.fi
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Applied Quaternary research in the central part <strong>of</strong> glaciated terrain,<br />
edited by Peter Johansson and Pertti Sarala.<br />
<strong>Geological</strong> <strong>Survey</strong> <strong>of</strong> <strong>Finland</strong>, <strong>Special</strong> <strong>Paper</strong> <strong>46</strong>, 55–62, 2007.<br />
LATE WEICHSELIAN SHEETFLOW DRAINAGE OF SUBGLACIAL<br />
LOKKA ICE LAKE<br />
by<br />
Raimo Sutinen 1 , Mari Jakonen 2 , Pauliina Liwata 1 and Eija Hyvönen 1<br />
Sutinen, R., Jakonen, M., Liwata, P. & Hyvönen, E. 2007.<br />
Late Weichselian sheetfl ow drainage <strong>of</strong> subglacial Lokka ice<br />
lake. Applied Quaternary research in the central part <strong>of</strong> glaciated<br />
terrain. <strong>Geological</strong> <strong>Survey</strong> <strong>of</strong> <strong>Finland</strong>, <strong>Special</strong> <strong>Paper</strong> <strong>46</strong>, 55–62,<br />
6 <strong>fi</strong> gures.<br />
A conceptual model regards arboreal eskers as products <strong>of</strong><br />
time-transgressive glaci<strong>of</strong>l uvial deposition within close proximity<br />
<strong>of</strong> the retreating ice margin. In contrast, an anastomosing<br />
network <strong>of</strong> tunnel valleys or esker tracks is attributed to subglacial<br />
fl ood events, but the outburst release mechanisms <strong>of</strong> former<br />
subglacial meltwater bodies have remained obscure. We studied<br />
an anastomosing network <strong>of</strong> esker tracks in Lokka, east-central<br />
Finnish Lapland. Sheetfl ow paleohydrography as compiled with<br />
a digital elevation model (DEM) and airborne gamma-ray (AGR)<br />
data disputes the concept <strong>of</strong> ice-marginal deposition, but the<br />
network displays evidence <strong>of</strong> subglacial mass-fl ows. The tracks<br />
show convex-up parts in their long pr<strong>of</strong>i les and cross topography<br />
regardless <strong>of</strong> slope indicating a subglacial origin beneath the Fennoscandian<br />
Ice Sheet (FIS). The alignment <strong>of</strong> the esker tracks,<br />
fanning out to southeast and south seems to be generated from a<br />
large subglacial reservoir beneath the FIS, and we propose that<br />
the former Lokka ice-lake had been the source <strong>of</strong> the sheetfl ow<br />
system. The coincidence <strong>of</strong> escarpments (DEM) and airborne<br />
magnetic (AM) anomalies suggests that neotectonic fault instability<br />
likely was the triggering mechanism for the outburst <strong>of</strong> the<br />
subglacial Lake Lokka.<br />
Key words (GeoRef Thesaurus, AGI): glacial geology, subglacial<br />
lakes, meltwater, drainage patterns, eskers, neotectonics, Pleistocene,<br />
Weichselian, Lokka, Lapland Province, <strong>Finland</strong>.<br />
1 <strong>Geological</strong> <strong>Survey</strong> <strong>of</strong> <strong>Finland</strong>, P.O. Box 77, FI-96101<br />
Rovaniemi, <strong>Finland</strong><br />
2 University <strong>of</strong> Oulu, Dept. <strong>of</strong> Geosciences, FI-90570<br />
Oulu, <strong>Finland</strong><br />
E-mail: raimo.sutinen@gtk.<strong>fi</strong> , marijako@mail.student.oulu.<strong>fi</strong><br />
pauliina.liwata@gtk.<strong>fi</strong> , eija.hyvonen@gtk.<strong>fi</strong><br />
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