808  E. Wilson—Unconformity of the Keuper and Bunter. 
TV.—On roe UnconrorMaBILiry or THE Kruper and Bunter. 
By E. Witson, F.G.S. 
Ce . following instance of the unconformability of the Keuper 
and Bunter divisions of the Trias, which came under my 
notice during the construction of the Great Northern Derbyshire 
Extension line in the year 1877, is deserving of notice, not only 
from its decided rarity,' but also from its exceptional clearness. 
In the railway tunnel cuttings at Morley, near Derby* (see Geol. 
Surv. Map, 71 N.W.), the Keuper, which consists of red marls with 
thin beds of sandstone below, and red marls above (apparently 
representing the lower portion of the Upper Keuper graduating 
down into the Lower Keuper), may be seen reposing on a well- 
levelled surface of the Bunter Pebble Beds. 
On the east side, at the tunnel entrance, the Keuper dips a little 
north of west at an angle of 4° or 5°. The dip of the Bunter at this 
point (as defined by a band of marl which separates the Lower 
Mottled Sandstone from the Pebble Beds) is nearly due west at 7° 
or 8°. Going east, the westerly dip of the Keuper increases to from 
6° to 8°, and that of the underlying Bunter to 10° or 12°. Coinci- 
dently with this difference in dip the Pebble Beds are visibly over- 
lapped on the east in a space of three chains, to an extent repre- 
sented by a diminution from thirty-eight to twenty-five feet—the 
total thickness of this subdivision of the Trias! The Pebble Beds 
are succeeded by the Lower Bunter, which consists of about a 
hundred feet of false-bedded sandstone with three broad bands of 
brecciated conglomerate in its lower portion. The Lower Mottled 
Sandstone, which, like the Pebble Beds, dips west, at from 12° to 
14° or 15°, rests with a pronounced unconformity on the truncated 
edges of purple and light blue shales of the Lower Coal-measures 
that dip in a contrary (easterly) direction at an angle of 12°° (see 
Fig.). 
At Morley village, half a mile north of the railway, Upper Keuper 
Marls may be seen in the road cuttings resting directly (and without 
an appreciable dip) on an eroded surface of the Lower Bunter Sand- 
stone, which, with a brecciated base, reposes on deep red Coal- 
measure shales, similar to those exposed in the Morley tunnel 
cutting? The Lower Bunter Sandstone must be here considerably 
reduced in thickness, for between the outcrop of the Coal-measures 
and of the Keuper there is not room for more than fifteen feet or so 
of that rock. The disappearance of the Bunter Pebble Beds, and 
1 o . Ter . . . 
i ee ey around Wigan, Mem. Geol. Sury. p. 31. Triassic 
2 This interesting section is within an hour’s walk of either Breadsall or West 
Hallam Stations on the Great Northern Railway. 
’ The dips in the section do not correspond with those here given, because the 
section is not taken along the true line of dip. 
4 Tt was the fancied textural resemblance of these red rocks of the Lower Bunter 
Sandstone and Coal-measures to Rothliegende, which appears to have led the 
Government surveyors to club them together and map them as Permian Lower Red 
Sandstone. At Dale Mill a similar mistake was made with characteristi i = 
bedded Coal-measure sandstone. SCT ead 
