rock fault," along which the Triassic rocks are brought in on the west.
It will be observed that along this anticlinal the lower beds of the Yoredale group, immediately overlying the Mountain Limestone, are brought to the surface, this latter rock itself being found at Astbury, at the base of Congleton Edge, but not in the line of the section*.
As regards the age of this anticlinal, we are, fortunately for our purpose, not left in doubt. Not far to the eastward is the Permian outlier of Hug Bridge, near Rushton Spencer, where, as already stated, sandstones and marls of Permian age rest immediately on the Yoredale beds. We have here, therefore, an illustration, similar to that of Clitheroe, in North Lancashire, of disturbances accompanied by enormous denudation of the Carboniferous rocks at the close of the Carboniferous period, and antecedently to that of the Permian. The amount of denudation in this instance may be thus estimated†: —
feet.
[Upper 1000
Coal-measures < Middle 4000
[Lower 1000
Millstone Grit Several divisions 1000 Yoredale Series (in part) . Several divisions 2000 9000
The easterly prolongation of the anticlinal of the river Dane cannot be very clearly traced, owing to the rearrangement of the Carboniferous beds along the lines of disturbance in a meridional direction (north to south) at the close of the Permian period. As already shown on a former occasion‡, the series of foldings along axes ranging from west to east into which the Carboniferous rocks of the North of England were thrown at the close of the Carboniferous period have been modified by two subsequent lines of disturbance at the close of the Permian and Jurassic periods respectively ; but the whole three systems bear a close physical relationship in time and direction to each other. In the district bordering the Mountain Limestone of Derbyshire the intersection of these lines of disturbance, accompanied and followed, as they have been, by several denudations, have complicated the structure of the rocks as it originally existed at the beginning of the Permian period. Hence the difficulty of following out the course of the anticlinal of the Dane eastward ; nevertheless it may, I think, evidently be traced
- A detailed description of the beds in this district will be found in " The
Geology of the Country around Stockport," &c., by Messrs. Hull and Green. Mem. Geol. Survey, pp. 69-74.
† The thickness of the Coal-measures is that ascertained by the Geological Survey as applying to North Staffordshire, which is less than that of Lancashire. The thickness of the Millstone Grit and Yoredale beds is that given in the Memoir, on "the Geology of Macclesfield," &c., above quoted (see p. 85). The above estimates are probably rather under than over the truth.
‡ " On the relative Ages of the Physical Features," &c., supra cit.
VOL. XXV. PART I. O
