Monitoring the thermal state of permafrost by automated time-lapse Capacitive Resistivity Imaging
At the University of Sussex Permafrost Laboratory, geophysical experiments are being set up as part of the Natural Environmental Research Council (NERC) Technology Proof of Concept Programme. The aim of the experiments is to test the technical feasibility of undertaking time-lapse tomographic measurements using permanent, in-situ capacitive sensors to remotely monitor permafrost temperatures. The sensors are placed on the rock surface, as distinct from galvanic sensors drilled into the rock and subject to ice-induced disturbance or variable electrical contact. Results from capacitive sensors will be compared with those from galvanic electrodes used for time-lapse Electrical Resistivity Tomography (ERT) in blocks of soft and hard limestone subject to one-sided and two-sided freezing. It is hoped that this will lead to significant improvements in monitoring capability, both for permafrost simulation experiments in the laboratory and for practical applications in the field (e.g. monitoring of thaw-sensitive alpine permafrost in Europe). The research is funded by a NERC grant to Oliver Kuras, Paul Wilkinson, Phil Meldrum, Ed Haslam and Simon Holyoake (British Geological Survey), Julian Murton (University of Sussex) and Michael Krautblatter (University of Bonn), and is being carried out by this interdisciplinary team, which also includes Tim Cane, Phil Watson and Barry Jackson (University of Sussex).
The interactions of past permafrost and glaciers was a major theme of a Glaciotectonics Workshop that took place from 11th to 15th September 2011 at Sheringham, North Norfolk, UK. The complex polydeformed glacial and pre-glacial sediments exposed in the coastal sections of North Norfolk provided an ideal location and natural laboratory that brought expertise in glacial geology, structural geology, permafrost stratigraphy and state-of-the-art imaging of sediment microstructures. The workshop comprised a fertile mixture of talks and field visits. A prominent theme proposed by Richard Waller (Keele), Emrys Phillips, Jonathan Lee (British Geological Survey), David Vaughan-Hirsch (University of Southampton) and Julian Murton was the identification of geological evidence for coupling between a Middle Pleistocene ice sheet and permafrost beneath its margin, in the form of sand intraclasts within a glaciotectonic mélange (Figures 1 and 2; Waller et al., 2011) and rafts of chalk bedrock measuring tens of metres in length (Figure 3). The workshop was sponsored by the Quaternary Research Association, the Glacial Landsystems Working Group and the Subglacial Permafrost Task Force of the International Permafrost Association. It was organized by Emrys Phillips, Jonathan Lee and Hannah Evans (British Geological Survey), who have also edited a field guide on the topic:
Phillips E, Lee JR, Evans HM. 2011. Glacitectonics - Field Guide. Quaternary Research Association. (available from: http://qra.org.uk/publications/field_guides)
Waller RI, Phillips E, Murton JB, Lee JR, Whiteman, CA. (2011). Sand intraclasts as evidence of subglacial deformation of Middle Pleistocene permafrost, north Norfolk, UK. Quaternary Science Reviews 30: 3481–3500.
Fig. 1 Sand intraclasts within a glaciotectonic mélange (the Bacton Green Till Member), West Runton, North Norfolk, UK. The intraclasts range from a few tens of centimetres to >10 m in length and have sharp contacts with the surrounding till. Preservation of primary stratification within the intraclasts is attributed to deformation at temperatures slightly below the pressure-melting point, when pore ice cemented the intraclasts as rigid bodies. At the same time deformation was concentrated into the surrounding finer-grained till because of its significant liquid water content and ductile rheology.
Fig. 2 A geological conundrum: the big question mark. This sand intraclast within the glaciotectonic mélange at West Runton invited participants of the Glaciotectonic Workshop to identify its origin and palaeoenvironmental significance. Please send your answers to Richard Waller.
Periglacial and Glacial Engineering Geology Working Party
The Working Party on Periglacial and Glacial Engineering Geology—part of the Engineering Group of the Geological Society of London—has submitted a book proposal to the society. The book’s aim is to provide an essential reference handbook for professionals working in relict periglacial and glacial ground conditions, as well as a valuable textbook for students and others. The Steering Group of the Working Party comprises John Charman (Chair), Chris Martin (Secretary), Dave Giles, Julian Murton, Kevin Privett and Mike Winter. For further information, contact Chris Martin (Christopher.Martin@uk.bp.com).
Julian Murton (firstname.lastname@example.org)
Fig. 3 Two stacked rafts of white chalk bedrock (note flint bands within them) separated by and overlain by unconsolidated sand and gravel of the Wroxham Crag Formation, Overstrand, North Norfolk, UK. The detachment of the chalk rafts is inferred to have occurred near the ice-sheet margin or proglacially, when permafrost was present in the chalk and overlying crag deposits.