Geology of the Tisbury district (Wiltshire), 1:10000 sheet ST92NW, and the Jurassic of ST93SW : part of 1:50000 sheets 297 (Wincanton) and 298 (Salisbury)

The Tisbury d i s t r i c t lies at the western end of the Vale of Wardour. The lowlying central part of the d i s t r i c t along the the valleys of the rivers Sem and Nadder is underlain by the Kimmeridge Clay (Figure 1). The Nadder Valley is flanked by the Portland Group which, on the north side of the valley, forms long dip slopes rising to a maximum height of about 216 m OD at West Tisbury. Cretaceous strata include a thin Lower Greensand and a somewhat thicker Gault, both of which are poorly exposed. The latter formation is involved in extensive landslips in the south-west of the d i s t r i c t . The Upper Greensand on both sides of the valley forms impressive escarpments, that on the south rising to over 200 m OD near Old Wardour, and that in the north rising to 230 m OD north of West Tisbury. The latter is the highest point in the d i s t r i c t . A small area of Chalk crops out in the south-east. The principal drainage is by the rivers Sem and Nadder in the south and central part of the d i s t r i c t and by several north-bank tributaries, mostly unnamed, but including the Oddford Brook on the west side of Tisbury. Soils developed on the Kimmeridge Clay and the Gault are heavy and poorly drained and are mostly under pasture. However, s o i l s on the Portland Group and Upper Greensand, especially on the Boyne Hollow Chert, are l i g h t and w e l l drained and given over to arable farmland. Woods, both deciduous and coniferous, occur principally on the steep scarp slope of the Shaftesbury Sandstone. Apart from a few light industrial units in Tisbury, agriculture is the only industry.