3. GEOLOGY, SOILS AND LANDCAPABILITYGeology, Soils and Land CapabilityUndulat<strong>in</strong>g Class 3 arable land, formed on till andfluvioglacial material <strong>of</strong> ORS (Devonian) lavas andsediments, Lomond Hills near K<strong>in</strong>rossGeologyFor <strong>the</strong> purpose <strong>of</strong> this handbook, <strong>the</strong>geology <strong>of</strong> <strong>the</strong> <strong>East</strong> <strong>of</strong> <strong>Scotland</strong> can besimplified <strong>in</strong>to three blocks: <strong>the</strong> MidlandValley, clearly demarcated from <strong>the</strong><strong>East</strong>ern Highlands by <strong>the</strong> HighlandBoundary Fault and, from <strong>the</strong> Sou<strong>the</strong>rnUplands, by <strong>the</strong> Sou<strong>the</strong>rn Upland Fault(Figure 3.1).• The Sou<strong>the</strong>rn Uplands, roll<strong>in</strong>g hills ris<strong>in</strong>gto altitudes around 600m, are relativelysimple geologically: predom<strong>in</strong>antlyshales and greywackes (metamorphosedabyssal f<strong>in</strong>e sandy sediments) <strong>of</strong> <strong>the</strong>Ordovician/Silurian (O/S) period, withsome sedimentary rocks <strong>of</strong> <strong>the</strong> Devonianand Carboniferous periods. The O/Srocks contribute little to <strong>the</strong> arable soils<strong>in</strong> Table 3.1.• The Midland Valley, is dom<strong>in</strong>ated bysandstones, calciferous sandstones,shales and limestones <strong>of</strong> <strong>the</strong>Carboniferous period (but without <strong>the</strong>thick Mounta<strong>in</strong> Limestone strata <strong>of</strong> <strong>the</strong>North <strong>of</strong> England). Between <strong>the</strong>se rocksand <strong>the</strong> Highland Boundary Fault aresandstones <strong>of</strong> <strong>the</strong> Devonian period (<strong>the</strong>“Old Red Sandstones” - ORS). There arealso very extensive <strong>in</strong>trusive andextrusive areas <strong>of</strong> igneous rocks,predom<strong>in</strong>antly basalt, notably <strong>in</strong> NorthFife, and <strong>the</strong> Lothians. Under glaciationand wea<strong>the</strong>r<strong>in</strong>g, <strong>the</strong>se rocks, and <strong>the</strong>Carboniferous rocks <strong>in</strong> particular, yieldedsoil-form<strong>in</strong>g materials <strong>of</strong> high basestatus and f<strong>in</strong>e texture. The ORS tendedto give coarser, typically dark red,materials <strong>of</strong> lower base status.• The <strong>East</strong>ern Highlands, more ruggedterra<strong>in</strong> ris<strong>in</strong>g to 1000m, are composedpredom<strong>in</strong>antly <strong>of</strong> ancient Dalradian(south) and Mo<strong>in</strong>ian (north)metamorphic rocks (various schists withgneisses, slates etc.: part <strong>of</strong> <strong>the</strong> landmass which <strong>in</strong>cluded much <strong>of</strong> N. Canada,Greenland, Norway & Sweden), withsubstantial areas <strong>of</strong> <strong>in</strong>trusive andextrusive igneous rocks (granite andgabbro). There is an important nor<strong>the</strong>rnfr<strong>in</strong>ge <strong>of</strong> ORS, which is <strong>in</strong>ternationallyfamousas a source <strong>of</strong> fossils <strong>of</strong>Devonian fish. Under glaciation andwea<strong>the</strong>r<strong>in</strong>g, <strong>the</strong> Dalradian and Mo<strong>in</strong>ianrocks yielded a great variety <strong>of</strong>predom<strong>in</strong>antly coarse and base-poor soilmaterials, but, <strong>in</strong> mixture with igneousrocks, could give base-rich materials.The last glaciation <strong>of</strong> <strong>Scotland</strong> wascomplete and extensive, leav<strong>in</strong>g deep layers23
<strong>Crop</strong> <strong>Production</strong> <strong>in</strong> <strong>the</strong> <strong>East</strong> <strong>of</strong> <strong>Scotland</strong>Figure. 3.1 Simplified geological map <strong>of</strong> <strong>Scotland</strong>Reproduced by permission <strong>of</strong> <strong>the</strong> British Geological Survey. ©2000 NERC. All rights reserved24