MESOZOIO STRATA.
Cretaceous System.
Chalk (500 feet thick).—It constitutes the Weld Hills. This is usually a harder rock than that of the south of England, and the nodular flints which it contains are scattered through a great part of its thickness. The lower part assumes in places a grayer and softer aspect. Fossils occur iu the upper part, especially sponges, marsu pites, and Echinedermata, but Mollaca and Conchifera are less plentiful than in the south of England. The lowest band of the chalk is red, as in Lincolnshire. The chalk is unconformed to all the strata below, resting on each of them in succession in different parts of the Wold edge, as far as the lower beds of the has.
Speeton Clay (150 feet thick 1).—This blue argillaceons deposit lies under the chalk, but does not graduate into it. It appears on the coast at Speeton, and inland at Knapton and other points. The organic remains are numerous, different from those in the chalk, and also different from those in the strata below. They appear to have analogies to the ganit of the south of England, and also to the Kim meridge clay ; the former analogies perhaps predominate. Some of the shells occur in the ‘Neocomian' formations of France, which are supposed to be nearly equivalent to our lower greensand.
Oolitic System.
Kimmeridge occurs along the north side of the Vale of Pickering, and under the escarpment of the Wolds, near Cave. It is not clearly seen in contact with the Speeton clay above, into which it gradually passes. It contains °area delloidea.
Upper Calcareous Grit (60 feet thick).—This is seen on the hills above Wass Bank, and near Pickering. It contains a few fossils.
Coralline °dile (60 feet thick).—This rock forms generally the uppermost itratom of the ranges of tabular hills which extend from Scarborough to the Hambleton hills, and then turns southward to Walton and Acklam. Its oolitic grains are of various size; some beds beiug coarse pisolite. A few bands of chert nodules occur in it, and crystallisation' of cale-spar and quartz, and deposits of chalcedony, lie in the cavities left by the decomposition of organic remains. It
is not generally durable in buildings. In this rock Is situated Kirk dale Cave. Several rivers sink into it, and reappear after long sub terranean passages. The organic remains are extremely numerous; the coral bands being local, but characteristic.
Lower Cakareous Grit (80 feet thick).—It forms the edges of the tabular hills above mentioned, and occasionally broad and very poor heath surfaces. Though called calcareous, it has little of carbonate of lime in its composition, and some of the shells which it contains are silicified. Locally it la a good building-stone. The fossils are very numerous, and almost exactly like those of the same rocks in Oxford shire. A nasonita reriebralie is common.
Oxford Clay, or Croy Earth of Scarborough Castle Hill (150 feet thick).—It appears in the steep slope of the escarpments of the tabular hills, under the ' Nab Ends,' and on the breast of the sea-cliffs south of Scarborough. The fossils which it yields are more like theme of the calcareous grit than those of the Oxford clay of the south of England.
Kellotsuys Rock, or Ilackness Rock (90 feet thlck).—It lies at the base of the tabular hill", and at the foot of the sea-cliffs south of Scar borough. It is more ferruginous than the calcareona grit ; is in places somewhat oolitic, and everywhere rich In fossils, such as Anneenitea eulioriensis, A. sublayie, Oryphera dilatata, and other "bell, character istic of tho same rock In Wiltshire, where It is much thinner and of less importance. The neckties, rock has proved a fair building-stone in the museums at York and Scarborough.
Cornbrash (10 feet thkk).—This impure calcareous rock is separated from the sandy Kelloways atone by • thin band of clay containing Onweacea. It is Ter7 rich in fossils, and is nearly continnons from Scarborough to the vicinity of Mahon.