Crop Production in the East of Scotland - SASA

3. GEOLOGY, SOILS AND LANDCAPABILITYGeology, Soils and Land CapabilityUndulating Class 3 arable land, formed on till andfluvioglacial material of ORS (Devonian) lavas andsediments, Lomond Hills near KinrossGeologyFor the purpose of this handbook, thegeology of the East of Scotland can besimplified into three blocks: the MidlandValley, clearly demarcated from theEastern Highlands by the HighlandBoundary Fault and, from the SouthernUplands, by the Southern Upland Fault(Figure 3.1).• The Southern Uplands, rolling hills risingto altitudes around 600m, are relativelysimple geologically: predominantlyshales and greywackes (metamorphosedabyssal fine sandy sediments) of theOrdovician/Silurian (O/S) period, withsome sedimentary rocks of the Devonianand Carboniferous periods. The O/Srocks contribute little to the arable soilsin Table 3.1.• The Midland Valley, is dominated bysandstones, calciferous sandstones,shales and limestones of theCarboniferous period (but without thethick Mountain Limestone strata of theNorth of England). Between these rocksand the Highland Boundary Fault aresandstones of the Devonian period (the“Old Red Sandstones” - ORS). There arealso very extensive intrusive andextrusive areas of igneous rocks,predominantly basalt, notably in NorthFife, and the Lothians. Under glaciationand weathering, these rocks, and theCarboniferous rocks in particular, yieldedsoil-forming materials of high basestatus and fine texture. The ORS tendedto give coarser, typically dark red,materials of lower base status.• The Eastern Highlands, more ruggedterrain rising to 1000m, are composedpredominantly of ancient Dalradian(south) and Moinian (north)metamorphic rocks (various schists withgneisses, slates etc.: part of the landmass which included much of N. Canada,Greenland, Norway & Sweden), withsubstantial areas of intrusive andextrusive igneous rocks (granite andgabbro). There is an important northernfringe of ORS, which is internationallyfamousas a source of fossils ofDevonian fish. Under glaciation andweathering, the Dalradian and Moinianrocks yielded a great variety ofpredominantly coarse and base-poor soilmaterials, but, in mixture with igneousrocks, could give base-rich materials.The last glaciation of Scotland wascomplete and extensive, leaving deep layers23