Julien Moreau, Aberdeen University (United Kingdom)
Adriaan Janszen, TU Delft (Netherlands)
Paul van der Vegt, University of Cambridge (United Kingdom)
Philip L. Gibbard, University of Cambridge (United Kingdom)
Mads Huuse, Aberdeen University (United Kingdom)
Andrea Moscariello, TU Delft (Netherlands)
Sub- to proglacial sediment transfer and associated ice-sheet behaviour is one of the most challenging topics of glaciological studies. The meltwater drainage system is responsible for a large part of the sediment transport from the ice-sheet base to the proglacial sedimentary system. It is now documented that subglacial meltwater is also driving ice-sheet behaviour, including the advances and retreats of ice masses. Apart from recent advances in remote sensing methods, active subglacial drainage systems are very hard to constrain and observe due to their extremely dynamic nature and obscure location underneath ice sheets. Therefore, models of subglacial meltwater systems are often assessed by analogy with the record of former glaciations. An outstanding feature of the meltwater systems associated with past glaciations is the occurrence of tunnel valleys, which are particularly well documented in the North Sea Pleistocene.
Tunnel valleys are also common in the Late Ordovician and Permo-Carboniferous record. Palaeozoic glaciogenic deposits are implicated in petroleum systems in North Africa and South America. In these systems, tunnel valleys and associated depositional elements constitute important oil reservoirs, often characterised by a complex sedimentary architecture. This paper presents initial results from a joint industry-academia project which aims to establish reservoir models for the NW European Pleistocene record and utilise these as analogues for the more poorly documented reservoirs of the Late Ordovician glaciogenic succession in North Africa.
The glaciogenic reservoir analogue studies project (GRASP) is a collaborative project focusing on the record of Pleistocene glaciations in NW Europe and principally in the North Sea and the surrounding onshore areas. Tunnel valleys and associated proglacial depositional systems are studied using diverse data types: high resolution bathymetry, offshore 3D seismic and high-resolution 2D seismic data, outcrop studies, and groundwater borehole data. The project aim is, by integrating the different type of data, to build a comprehensive model of the Pleistocene North Sea glacial system and compare it to the ancient glacial rock record, both in terms of regional evolution and in terms of glaciogenic reservoir geometries.
The first results emphasise differences between areas dominated by subglacial meltwater and areas dominated by ice streams, such as their association with sedimentary basins in the substrate. Several observations of the valley infill show clinoforms prograding towards the ice sheet centre. Our study provides insights into the facies changes associated with these clinoforms, and the integration of diverse techniques and datasets should enable us to establish a robust model of tunnel valley formation, distribution and infill architecture.