Page:VCH Rutland 1.djvu/39

 GEOLOGY bered that the rocks indicated are not everywhere exposed at the surface. This is especially the case with the Lincolnshire Limestone, large tracts of which are buried beneath accumulations of Boulder-Clay and Gravel. It so happens however that more of it is exposed in Rutland than in the adjacent part of Northampton, and as it underlies the greater part of the eastern half of the county from Barrowden on the south to Thistleton on the north, and from Barnsdale Hill on the west to Stamford on the east, it will be seen that this limestone is a prominent feature in the geology of the county. The limestone produces a light soil of a bright red colour, and Professor Judd has remarked that the county probably acquired its name of Rutland (i.e. red land) from the prevalent colour of its soil, for not only the Lincolnshire Limestone, but the Northampton Sands and the Marlstone Rock (see p. 3.) also produce red soils, and these soils have been washed down the clay slopes below the outcrops of the rocks which produce them. The Lincolnshire Limestone has been extensively quarried for building-stone at Ketton, Casterton, Stamford and Clipsham, as well as at Barnack, Wittering and Wansford in Northamptonshire. Professor Judd remarks that the freestones are of greater value when quarried from under the clays of the Upper Estuarine Series, that of Ketton being specially famous for its strength and durability. This Ketton stone is a bed of yellowish oolite from 3 to 4 feet thick, and has been employed in many of the ancient and modern buildings at Cambridge, Bury St. Edmunds, Bedford and Stamford, and also in Ely and Peterborough Cathedrals. THE GREAT OOLITE SERIES Throughout the counties of Northampton, Rutland and Lincoln the Great Oolite presents a regular sequence of beds, consisting of four well marked groups, two of which are limestones and two are clays. In ascending order these groups are known as (i) Upper Estuarine Series ; (2) Great Oolite Limestone ; (3) Great Oolite Clay, and (4) Cornbrash. Only a small portion of the main outcrop of these beds comes within the limits of Rutland, but outliers of them form hills near Barrowden, Ketton, Casterton, Pickworth and Clipsham. (i) The Upper Estuarine Series. — At the base of this group there is generally a layer of brown nodular ironstone, which either rests directly on the Lincolnshire Limestone or is separated from it by a thin layer of white marly clay. Though only from i to 3 feet thick this ironstone is generally a conspicuous feature in exposures of this horizon, and the upper surface of the Limestone shows signs of having suffered a certain amount of erosion before the formation of the ironstone. Such current erosion may have been caused by a slight general uplift of the area of deposition and a consequent shallowing of the water, or by the deflection of the current from a neighbouring river. In whatever way the change was brought about it is certain that the whole area, which 7