Characterisation of Quaternary sediments from East Anglia

This report describes the mineralogical investigations of Quaternary sediments,mainly Cromer Till, collected from East Anglia. The main aim of the work was to characterise the mineralogical and physical properties of the till samples to facilitate correlation between tills from different localities. The clast composition of the samples was determined using a binocular microscope and the mineralogy of the matrix was determined using X-ray diffraction and thermogravimetry. Calibration charts were used to quantify the amount of quartz and calcite present. Cumulative frequency graphs were plotted from the particle-size data to determine the mean, median, standard deviation and skewness. Also ternary sand/silt/clay diagrams were plotted. The Cromer Till samples typically contained 2% gravel (mainly flint, sandstone, quartz and chalk), 45% sand, 31 % silt and 22% clay. The Starston Till contained 12% gravel (mainly flint), 46% sand, 16% silt and 26% clay. The 'Clay' from Sea Palling contained 1 % gravel (mainly flint), 10% sand, 78% silt and 11 % clay. The Lowestoft Till samples had different particle-size distributions and the gravel consisted mainly of chalk.The Crag Clay samples contained 1 % gravel (mainly sandstone), 11 % sand, 49% silt and 39% clay. The Blue Clay samples contained virtually no gravel, 4% sand, 59% silt and 37% silt. The Holocene sample contained 1 % gravel (mainly flint), 21% sand, 39% silt and 39% clay. The CaC03 contents and particle-size distributions of the Cromer Till samples were compared with published data (Lunkka, 1994). Based upon this comparison the samples were tentatively classified as either Walcott Diamicton, Happisburgh Diamicton or Norwich Brickearth. The 'Blue Clay' samples were also tentatively classified as Crag Clay. Recommendations for further work include detailed logging and sampling of coastal sections; collection of large samples for more accurate clast analysis ; and heavy mineral analysis.