Page:A Treatise on Geology, volume 1.djvu/195

 CHAP. VI. (sometimes internally blue) oolitic limestone there occurring is associated not only with dark shales (clunch), and light marly beds., altogether of a considerable thickness, at least 100 feet, but is also overlaid by an important deposit of red, whitish, and greenish argillaceous strata, altogether of the same nature as the "old red formation" of the vicinity. The whole series of the south Clee hills may be thus expressed in general terms:—



Admitting the limestone and shale beds (b, c, d, e) to be the equivalent of the lower scar limestone (Derbyshire limestone) of the north of England, the quartzose conglomerate (g) may be ranked as millstone grit; and the red and white clays (f) must be considered as a recurring bed of the old red marl, interpolated among the carboniferous rocks, just as the red grits and clays of Orton and Ravenstone dale have been described as marking one form of a transition between the old red sandstone and the carboniferous formation, on the border of the primary districts of Westmoreland.