Geoscience Reference
In-Depth Information
assic and Early Jurassic units. In the early days of geological exploration, the Middle
Jurassic succession was divided by William Smith (Chapter 6, Area 9) into an Inferi-
or Oolite unit and a Great Oolite unit. The Inferior Oolite lies below the Great Oolite,
but there is much variation from place to place in the detailed nature of these bed-
rock materials. Limestones, of particular importance in producing steep slopes in the
scenery, alternate in the successions with mudstones and sandstones. Special mention
should also be made of the Northampton Sandstone layer (forming the local base of
the Middle Jurassic), in which ironstones have been of great importance economically,
particularly in the southwest of Area 15 around Market Harborough and Corby. This
variable package of Middle Jurassic bedrock, rarely more than 50 m thick in total, has
been eroded into isolated hills in the west but forms whole valley sides further east,
where the tilt has brought it down to lower elevations. Many of these incised valleys
have rather parallel sides and trend roughly east-west, a pattern that may indicate that
the early streams formed on easterly sloping surfaces.
Rutland Water, near Oakham, was created in 1977 by the construction of a dam
across two such easterly-trending branches of the River Gwash. The Gwash has eroded
downwards through the Middle Jurassic limestones into the underlying Northampton
Sandstone and Early Jurassic mudstones. The limestone has been used in building the
older houses in the village of Edith Weston, shown in the foreground of Figure 270.
The Middle Jurassic limestone has also provided stone for many of the buildings
throughout Landscape B , whether in villages or stately mansions. The building of
Burghley House (Fig. 271) was begun in 1555, largely using the locally quarried Lin-
colnshire Limestone of Middle Jurassic age. It has been the home of the Cecil family
ever since.
FIG 270. Northwesterly view across Rutland Water from the village of Edith Weston.
(Copyright Aerofilms)
North of Stamford, between Bourne and Sleaford, a number of low hills are un-
derlain by Late Jurassic Oxford Clay, often capped by Anglian ice-laid material. Ero-
sion here has carved numerous 30-40 m deep valleys, cut through the Anglian material
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