Oolitic series, by streams which probably flowed from W. to E. During the Glacial period this valley was filled with immense deposits of the Boulder-clay and its associated beds ; and on the re-emergence of the land from beneath the Glacial sea, the present rivers (the Derwent and its affluents), flowing from E. to W. and cutting a narrow gorge through the harder strata of the Howardian hills, scooped out the valley again, but not to so great a depth as before *. Thus the clay-beds, which formed the bottom of the original valley, remain (especially in their eastern part) to a great extent concealed by drift- deposits, as represented in the ideal section
(Pl. XXIII. fig. 1).
Having pointed out the obstacles to complete examination of the inland development of the Neocomian beds of the district, I now proceed to describe in detail all the facts which I have been able to collect concerning them.
The deep ravine (" gill ") formed by the small stream which flows by the village of Reighton, is cut quite through the Boulder-clay ; and about half a mile below the village, beds of blue clay were found, yielding Belemnites lateralis, Phil., and many fragments of Ammonites and Ancyloceras. These beds are shown by their fossils to belong to the upper part of the Lower Neocomian (zone of Ammonites speetonensis).
From this point westward to the village of West Heslerton (see section, Pl. XXIII. fig. 2), a distance of fifteen miles, the base of the Wolds, as well as the bottom of the valley, is entirely covered and concealed by superficial deposits, and no opportunity is afforded for the study of the underlying strata. According to Young and Bird f, however, a boring one and a half mile south of Staxton showed, under 278 feet of white and red chalk, beds of blue clay or shale, which were pierced to the depth of 54 feet. The general dip of the strata being S.E., as we proceed westward the beds underlying the chalk gradually rise, and at length are seen at the base of the Wolds, above the great superficial deposits which fill the bottom of the valley.
In the western part of the parish of West Heslerton there were at one time several pits close to the Wold-foot, in which stiff blue clay was dug for dressing the loose sandy alluvial land of the dis- trict ; these, however, have been closed for many years, and I could obtain no evidence of fossils having ever been found in them. A little to the westward of these, however, on the boundary be- tween the parishes of West Heslerton and Knapton, there is a pit to which great interest attaches. At the bottom of a very deep chalk-quarry the underlying clay has been dug for the purpose of dressing the land. The section exposed was as follows : —
- " The Hartford brook or river " (one of the tributaries of the Derwent)
" rises on the very cliff near Filey, at a height of about 100 feet above the sea, and flows, westward, southward, and eastward, 100 miles before reaching it." — Prof. J. Phillips, ' Rivers, Mountains, and Sea-coasts of Yorkshire,' p. 85.
t ' Survey of the Yorkshire Coast,' p. 60 (1828).
