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Dating of Quaternary Fluid Flow Events |
1 Fluid Processes and Waste Management Group, British Geological Survey, Keyworth, Notts, NG12 5GG, UK
2 Hydrogeology Group British Geological Survey, Keyworth, Notts, NG12 5GG, UK
3 Mineralogy and Petrology Group, British Geological Survey, Keyworth, Notts, NG12 5GG, UK
During the Quaternary (the last 1.6 Ma), episodic groundwater flow occurred to depths of several hundred metres. In many regions, climatic fluctuations induced episodes of rapid and slow groundwater flow. The former, termed here ‘groundwater flow events’, were characterized by extensive fresh-water recharge, and flushing of pre-existing water. It is important to identify and characterize such events to: (i) calibrate predictive models for future flow, thereby underpinning Performance Assessments for underground waste repositories; (ii) establish what proportion of global fresh-water resources was recharged during early Holocene or Pleistocene flow; and (iii) help interpret the timing and nature of Pleistocene climatic changes. To date, hydrogeochemical, mineralogical and petrological data have been interpreted in terms of post-glacial Holocene groundwater flow, or pre-Quaternary palaeofluid flow. Typically, Pleistocene recharge before the last glacial maximum has been unresolved. The effect of any given Quaternary climate change on the flow of pre-existing groundwaters is rarely identified. This paper considers the methods available to date these flow events, and finds that mineralogical evidence has been under-used to interpret Quaternary groundwater flow. Used together with hydrogeochemical data, mineralogical observations offer the best prospect of improving our understanding of Quaternary groundwater flow events.
