^77 



AMONGST THE YORKSHIRE OOLITES. 



S. A. ADAMSON, F.G.S. 



A FIELD excursion of the Leeds Geological Association was held on 

 Easter Monday, in the neighbourhood of Malton. The locality has 

 long been of surpassing interest to geologists, from the beauty and 

 variety of its innumerable fossils, and from the splendid geological 

 sections to be found in quarries and cuttings. The leaders for the 

 day were Messrs. Samuel Chadwick and M, B. Slater. From North 

 Grimston Station the way was taken down the line to the quarry 

 where the ' cement stone ' is obtained. This is of great commercial 

 value, this hard stone yielding a good hydraulic mortar, and sold 

 as ^ blue lias lime,' this, of course, being an erroneous expression ; 

 still the character and the appearance of the beds have a great 

 resemblance to some of the lias beds of the south of England ; 

 indeed, when the Rev. P. B. Brodie visited this section, he stated 

 that had he been suddenly put down in this quarry, without knowing 

 the locality, he should have imagined he was at Lyme Regis, This 

 cement stone is a very hard, compact, argillaceous limestone, with 

 here and there partings of soft calcareous shales. This stone 

 evidently owes its origin to the denudation of the coral rag, to which 

 it is unconformable, as well as to the Kimeridge clay above. The 

 dip is but slight in this quarry, but lower down, nearer the railway, 

 it rapidly increases. These beds are really equivalent in geological 

 sequence to the upper calcareous grit further north, but, of course, 

 are widely different from a lithological point of view. From this 

 quarry the ascent of North Grimston Wold was made, passing over 

 the Kimeridge clay and arriving at the white chalk. The red chalk 

 is also present between these two formations, but no section of this 

 was noted. In a quarry on the wold a fine section of the flint-bearing 

 or lower chalk was examined. Here the familiar tap of the hammer 

 was soon heard, and many flint nodules broken to examine the 

 beautiful fossil sponges they contain. It is a most interesting bit of 

 geology to observe how the silica, once held in solution in the 

 cretaceous ocean, has segregated around these ancient sponges, and 

 preserved them so perfectly and so beautifully, as we may see by 

 the lens. Some large and good specimens of the characteristic 

 Inoceramus were obtained. Some very peculiar markings in the 

 chalk were attentively examined. They appeared to be of a long, 

 needle-shaped, partially fibrous nature ; but it was impossible by the 

 aid of a pocket lens to determine conclusively whether they were 



June 1887. N 



