OR/15/064 Summary

From Earthwise
Jump to: navigation, search
Ford, J R, Hughes, L, Burke H F and Lee, J R. 2015. The Vale of Pickering: an initial summary of the Quaternary/superficial geology and data holdings. British Geological Survey Internal Report, OR/15/064.

This desk study of the Quaternary geology of the Vale of Pickering has considered a range of existing datasets held by the BGS, including maps, superficial thickness and rockhead models and selected borehole information. The latter has been synthesised as a series of interlocking schematic cross sections. This study has been undertaken to provide a ‘conceptual geological’ model for the area to support the selection of groundwater monitoring sites for the BGS-led Environmental Baseline Monitoring project.

The geological cross-sections presented in this study consider a variety of baseline data including borehole logs and surface geological mapping. The interpreted geology shown is informed by the geologists’ tactic knowledge and conceptual understanding of the local geology.

Key outcomes of the work are as follows:

  • The study has identified considerable lithological heterogeneity in the lacustrine deposits including: a lower fine-grained facies and an upper interbedded fine- and coarser-grained facies; the latter has been correlated primarily in the south and east part of the Vale.
  • The interbedded facies is inferred to pass laterally into fine-grained facies.
  • ‘Lenses’ of sand and gravel have been identified in the fine-grained facies. Although these are modelled as lenses in the cross-sections, they may represent bodies of sediment that are channelized and that extend for a greater distance away from the section.
  • Beds of sand and gravel have been identified in the interbedded facies that have been correlated between boreholes for several kilometres.
  • Basal sand and gravel is inferred to be present over a considerable part of the Vale. These deposits are in part inferred to be contiguous with equivalent deposits that are mapped at surface on the edges of the lacustrine deposits and at higher elevations on flanks of the Vale.
  • The till deposits are inferred to be mostly restricted to highly dissected patches on the topographic highs and the mapped areas on the periphery of the Vale; the lacustrine deposits are believed to overlie the till. This study has not identified any large areas of concealed till at depth in the Vale.
  • The subsurface/concealed Quaternary geology is likely to be locally heterogeneous, with a level of complexity that is not apparent in the published superficial mapping of the area nor captured by the current set of schematic cross sections.
  • The thickness of superficial deposits depicted in the cross sections differs considerably from that shown in the SDTM model in some parts of the Vale.