Significance
Understanding tunnel valleys is important because:
- They serve as a marker for areas with the potential for effective oil exploration in Africa,
- Their bedrock boundaries and glacial infill makes them effective aquifers in many regions.
- Soil engineers must accommodate the variations which they exhibit when boring tunnels, establishing foundations, and
- They provide one of several signatures marking the edge of former glaciations.
Tunnel valleys play a useful role in identifying oil rich areas in Arabia and North Africa. The Upper Ordovician–Lower Silurian materials there contain a roughly 20 m (66 ft) thick, carbon-rich layer of black shale. Approximately 30% of the world's oil is found in these shale deposits. Although the origin of these deposits is still under study, it has been established that the shale routinely overlies glacial and glacio-marine sediment deposited ~445 million years before the present by the Hirnantian glaciation. The shale has been linked to glacial meltwater nutrient enrichment of the shallow marine environment. Hence the presence of tunnel valleys is an indicator of the presence of oil in these areas.
Tunnel valleys represent a substantial fraction of all melt-water drainage from glaciers. Melt-water drainage influences the flow of glacial ice, which is important in understanding of the duration of glacial–interglacial periods and aids in identifying glacial cyclicity, a problem that is important to palaeoenvironmental investigations.
Tunnel valleys are typically eroded into bedrock and filled with glacial debris of varying sizes. This configuration makes them excellent at capturing and storing water. Hence they serve an important role as aquifers across much of Northern Europe, Canada and the United States. Examples include Oak Ridges Moraine Aquifer, Spokane Valley-Rathdrum Prairie Aquifer, Mahomet Aquifer, the Saginaw Lobe Aquifer, and the Corning Aquifer.
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