Age and provenance of the metasediments of the Monian Supergroup

Staff: J.M. Horák [with Dr Jane Evans, NERC Isotope Geology Laboratories and Dr Ulf Linnerman, Natural History Museum, Dresden].

The Monian Supergroup is a thick succession (estimated at 7km) of sedimentary rocks found in North Wales. As some sediments are rather like geological dustbins, taking in detritus from other eroding rocks, studying their content provides valuable information about the sedimentary and plate tectonic environment at the time, and constrains the age of deposition. Two separate studies are being undertaken under this general project:

  1. A geochemical study (whole-rock major and trace element analysis) and isotopic analysis (Sm-Nd) of the Monian Supergroup succession to determine and compare the source of the sediment in the three sub-units. The sample analysis is almost complete and contrasts between units have been noted.
  2. Dating the age and provenance of the New Harbour Group, the middle unit of the Monian Supergroup. These sediments contain no fossils so detrital zircons have been extracted and analysed for U-Pb isotopes to determine their age of formation. The sediments can be no older than the youngest crystal, this constrains the age of deposition.