The various sections obtained in the Acre-House Mine show that the thickness and order of succession of the different beds change very rapidly within short distances. The upcast shaft gave the following section from above downwards : —
ft. in.
(1) Soil 2 6
(2) White chalk 9 to 10
(3) Beds of yellow clay and red marly chalk 10
(4) Red sand 10
(5) Limestone rock, hard- and blue-hearted 14
(6) Blue clay, with the same fossils as the limestone above (Pecten cinctus abundant) 40
(7) Ironstone, soft and earthy above, solid and finely oolitic below (only the lower part is worked) 13 to 14
(8) Coarse greenish -white sands, in places indurated into hard sandstone-rock 6 to 7
(9) Very dark-coloured, highly bituminous, shaly clay. A thin bed at the top is remarkable for its highly inflammable character, and greatly resembles the Kimmeridge coal of the south of England.
In this section, 3 evidently represents the Hunstanton Red-rock (Gault?); 4, the upper sands (Upper Neocomian?); 5, 6, and 7, the Tealby series (Middle Neocomian) ; 8, the lower sand and sandstone (Lower Neocomian ?) ; and 9, the top beds of the Kimmeridge Clay.
The most interesting point about the above section is the great thickness of the clays 6, which in their mineralogical characters and fossil contents precisely resemble those of the Middle Neocomian at Speeton Cliff. As we proceed southwards the clays evidently become much thinner and subordinate to the limestones, while these last, on the other hand, are very extensively developed*.
IV. General Sketch of the Neocomian Beds of the North of England.
The most striking and remarkable circumstance in connexion with the stratigraphical position of the beds of Mesozoic age in Yorkshire and Lincolnshire, and that which it is always necessary to bear in mind in reasoning on their relations, is the grand unconformity which exists between the Cretaceous and Neocomian series (see section, fig. 2, and Table, p.331*). In consequence of this the chalk beds overlap all the Neocomian and Jurassic beds in succession quite down to the Lower Lias. Thus the Hunstanton Red-rock (the base of the Upper Cretaceous) is found lying in succession on Upper Neocomian at Speeton, on Lower Neocomian at West Heslerton, on Portlandian (?) at Knapton, on Kimmeridge clay at North Grimston, on Coralline Oolite at Leavening, and on Inferior Oolite at South
sand, each of which is coated with peroxide of iron, while the grains of the Lincolnshire and German ores are almost entirely made up of concentric coats of the last-mentioned substance.
- For much information concerning these Lincolnshire ores I am indebted
to W. Firth, Esq., of Leeds, the Managing Director of the Yorkshire Coal and Iron Company.
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