3804 Bernard Smith—Upper Keuper, East Nottinghamshire. 
colour (white, cream, grey-green, or pale-blue), but if thin may be 
stained pink externally. The shales often have the ‘ watered’ 
appearance characteristic of the Waterstones,’ and were evidently 
formed under the same conditions. Chocolate or bright-red marl 
frequently passes abruptly into bright-green marl in both a vertical 
and horizontal direction. Small galls of red marl up to half an inch 
in length frequently occur in the green shales and green ones in 
the red shales, and it is noticeable that the green shales are often of 
a coarser texture than the red. 
The Skerries.—Mr. W. H. Dalton? describes the majority of the 
sandstones in the Keuper Marl as “very fine-grained, compact, grey 
or even pure white, and very hard; in the latter case containing 
a high percentage of carbonate of lime . . . It is too soft for traffic, 
but hardens considerably by exposure, which permits of the deposition 
of crystalline carbonate of lime previously in solution in the pores of 
the stone. The cementing material appears to be wholly carbonate of 
lime, the rock falling into sand by submersion in hydrochloric acid ”’. 
He further adds that there are ‘‘thin bands of sandstone, sometimes 
rather coarse, soft, and of the same deep colour as the marls”’. 
These last-mentioned sandstones are thin and so scarce that they 
are almost unnoticeable, and pink in colour rather than deep red, like 
the marls. On hammering they generally expose a pale core, which 
suggests that the reddish tint is due to weathering. 
The skerries fall into three types in ascending order— 
1. Pale sandstones with carbonates. 
2. Pale flaggy sandstones with more silica. 
3. Coarse sandstones with larger rounded grains, mostly siliceous. 
1. These form the main stone horizon near the base of the division, 
and give rise to the most characteristic plateau features. They 
frequently exhibit drift-bedding and ripple-marking, or show a peculiar 
contorted arrangement of the lamine (suggestive at first sight of 
concretionary action). Here and there lumps of softer laminated 
stone lie rolled up and embedded in non-laminated portions and tend 
to weather out, giving the stone a honeycombed appearance. 
Two slices were examined microscopically, and in both cases the 
rock contained quartz and carbonates in about equal proportions. 
The first was a compact typical building stone (Maplebeck, Notts), 
slightly banded. It consists of small angular quartz-grains of very 
similar size and derived rhombs of dolomite. The dolomite never 
occurs as plates enclosing the quartz-grains, but as rhombs of various 
sizes, with rounded angles and broken faces. A little calcite may be 
present, but is not very much in evidence. The quartz-grains— 
generally less than 335mm. in diameter—are derived from plutonic 
rocks and are full of fluid cavities. The banded appearance is due to 
the scarcity of quartz, which drops from 50 to 10 per cent. along 
certain lines, and must therefore be due to sedimentation. 
The second example was a softer-looking ripple-marked rock, 
1 The term originally used by Mr. G. W. Ormerod, because the surfaces of some of 
the ‘beds had a watery appearance, like watered silk. 
2 
2 « The Geology of the Country around Lincoln ’’?: Mem. Geol. Sury., 1888, p. 8. 
