The generation of soil over sandstones in a periglacial environment A.M. Tye ⇑ , M.A. Ellis British Geological Survey, Keyworth, Nottingham NG12 5GG, UK article info Article history: Available online 22 March 2011 abstract The work examines the chemical and physical processes that are likely to have contributed to forming the soil thickness across the Sherwood Sandstone outcrop in Nottinghamshire, England, UK. The similarity in the extent of chemical weathering across the interface of the loosely compacted sand that forms the soil and regolith and the non-durable rock underneath suggests that physical weathering processes are required as the final part of the weathering process, essential to breaking the clay cement that maintains the structural integrity of the non-durable rock. With prior knowledge that the outcrop was the input point for water currently in the aquifer with ages between 10 and 35,000 a, periglacial processes such as ‘frost cracking’ and ‘active zone development’ are considered major influences on soil thickness. Ó 2011 British Geological Survey. Published by Elsevier Ltd. All rights reserved. 1. Introduction A soil’s thickness will affect its ability to store C, filter water and store essential nutrients. There are relatively few systematic stud- ies of soil thickness over large areas, and, therefore, existing soil formative models are typically not tested against rigorous spatially distributed data. Such data has now been extracted, however, from borehole logs held at the National Geoscience Data Centre at the British Geological Survey. These logs date back over 75 a and were examined to assess (i) the depth of weathering to bedrock (n = 500) and (ii) the depth of soil thickness (n = 280) across a major sand- stone outcrop and aquifer (Tye et al., 2010). The area examined comprises the Triassic Sherwood Sandstone unit in Nottingham- shire, UK, exposed over an area of 750 km 2 . Borehole logs reveal a weathering pattern derived from the engineering geology description of Spink and Norbury (1993) of (i) soil and subsoil, (ii) weak non-durable rock and (iii) durable bedrock. Spatial anal- ysis of the depth of weathering to bedrock shows that increased thickness of weathering exists in areas of high-density faulting in the underlying Carboniferous units. The pattern of faulting is determined by analyses of records of coal-seam abandonment. The process of enhanced weathering was likely driven by the fault- ing and associated fracturing acting as a drainage pathway for gla- cial/periglacial meltwater. The outcrop is a major recharge area for the Sherwood sandstone aquifer and evidence of periglacial waters exist in the aquifer (Edmunds et al., 1982). This abstract reviews current work which assesses the chemical and physical weathering processes that are believed to contribute to the soil thickness across the outcrop. 2. Material and methods Borehole data were collected from the National Geoscience Data Centre at the British Geological Survey. The weathering process was examined at a study site in Sherwood Forest, Nottinghamshire (Grid Ref: 461200 362300). Cores (diameter 7.5 cm) were ex- tracted from the study site to depths of 3 m. Samples of sandstone were collected from the Bestwood Quarry in Nottinghamshire, 10 km from the sample sites. Total soil element concentrations (including Ca, Mg, Na, K, Si, Al, Fe and Zr) were determined by X- ray Fluorescence analysis. Physical characteristics, such as bulk density, were determined from core material. A Panda Penetrome- ter was used to measure the changes in the resistance (MPa) through the soil/regolith at the site. 3. Results The archived borehole logs provide a means to review soil thickness across the area. Average soil depth was 1.8 m and med- ian soil depth was 1.5 m across the area (Tye et al., 2010). The fre- quency distribution of soil thickness is shown in Fig. 1. No relationships could be found between soil thickness and topo- graphic attributes (e.g., slope, aspect, curvature) (Tye et al., 2010). From the borehole logs, soil depths < 60 cm are common where the sandstone overlies Permian limestone on the western edge of the area. Soil depths > 4 m are rare and may possibly rep- resent earlier deposits. The majority of soil depths, however, are between 1 and 2.5 m. Because the Sherwood Sandstone Formation is a major aquifer in the UK, the weathering process in the rock has been extensively examined. Weathering of the sandstone largely involves the removal of Ca-carbonate and gypsum cements (Burley and Kantorowicz, 1986). Results from the XRF analyses showed that there was little difference in elemental concentrations of 0883-2927/$ - see front matter Ó 2011 British Geological Survey. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2011.03.050 ⇑ Corresponding author. E-mail address: atye@bgs.ac.uk (A.M. Tye). Applied Geochemistry 26 (2011) S139–S141 Contents lists available at ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem