Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/491

 reduced and altered form the 200 feet of clay forming the Lower Neocomian of Speeton ; it may be, however, that they are only to be regarded as a subordinate bed of the Tealby Series, in which case the Lower Neocomian must have entirely thinned out and disappeared in the forty miles which intervene between Knapton and Worlaby.

Near Clixby reappear beds from beneath the Chalk which more nearly resemble their equivalents in Yorkshire. These are blue clays containing large numbers of Pecten cinctus, Ancyloceras, and other fossils, but which differ from the Yorkshire Middle Neoeomian by being interstratified with subordinate beds of yellow sandy limestone and oolitic ironstones. As we proceed southwards, these latter beds become thicker and of greater relative importance, till at Tealby, Willingham, and Hainton, the ironstones having gradually disappeared, the clays become greatly diminished, and the limestones proportionately increased, the formation assumes, over a small area, an essentially calcareous character. As we still proceed southwards, however, we find this limestone formation gradually diminishing in thickness, and finally disappearing altogether.

The highest Neocomian beds, and those which reappear last from beneath the Lincolnshire Wolds, have assumed the arenaceous character which prevails in them throughout this country. Instead of blue clays, they consist of white or brown almost unfossiliferous sand and sandstone. These beds are persistent long after the lower portions of the series have disappeared, and, stretching southwards, pass into Norfolk, where they are known as the " Carstone," and contain at their base, as shown by Mr. Wiltshire *, the characteristic fossils of the Upper Neocomian.

Still further southwards occur the thin and anomalous but highly interesting fossiliferous deposits of Upware and Potton, which appear to form the link between the Neocomian deposits of the north and south of England.

V. Results of a General Comparison of the Neocomian Beds of Northern Europe.

Small as is the area occupied by the Neocomian strata now exposed in the North of England, there is abundant evidence that beds of this age were originally deposited to a great thickness over a very wide area in Northern Europe. A concurrence, however, of accidental circumstances (namely, the overlap of the Upper Cretaceous, the great spread of diluvial deposits over North-western Europe, and, finally, the great breach in the land formed by the North Sea) have caused the representatives of the Neocomian to be reduced to a few comparatively small and isolated patches.

Unlike their English equivalents, the continental beds are frequently much disturbed and even contorted, and the Neocomian strata usually form narrow strips along the flanks of hill-chains, the wide plains between which are covered with the widely spread


 * Quart. Journ. Geol. Soc. vol. xxv. p. 189 (1869).