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SUMMARY:Subglacial landscapes: Tunnel valleys in the central and northern 
 North Sea - Dr. Margaret Stewart\, Senior Scientist - Marine and Petroleum
  Geology\, British Geological Survey.
DTSTART:20191205T160000Z
DTEND:20191205T170000Z
UID:TALK134263@talks.cam.ac.uk
CONTACT:Frazer Christie
DESCRIPTION:Tunnel valleys are km-scale linear landforms formed subglacial
 ly and\, in the North Sea\, found offshore and associated with multiple gl
 aciations by the Quaternary ice-sheets. In this talk\, I present the use o
 f seismic reflection and gravity data to map more than a thousand buried t
 unnel valleys in the central and northern North Sea. The tunnel valleys ar
 e generally present from the seabed to depths of around 400 metres\, in a 
 study area of 180 000 km2 from 56°N to around 62°N. Buried tunnel valley
 s are well-imaged in seismic reflection data\, particularly in horizontal 
 timeslice in 3D seismic data. In gravity data\, the tunnel valleys appear 
 as small scale gravity lows\, likely due to their infill being less compac
 ted and potentially more porous than the surroundings.\n\nThis talks shows
  the most extensive study of tunnel valleys in the region to date\, with m
 ore than 20% of the study area containing buried tunnel valleys\, and also
  finds the longest tunnel valley recorded worldwide\, with large meanderin
 g tunnel valleys extending for more than 160 km. We also find tunnel valle
 ys further north than previously reported\, as well as a number of isolate
 d tunnel valleys extending towards and into the Norwegian Channel. As repo
 rted by other works in the region\, the apparently extensive networks of b
 uried valleys are found to be comprised of cross-cutting generations and t
 he next step in the puzzle is to link them to ice sheet dynamics.
LOCATION:Scott Polar Research Institute\, main lecture theatre
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