Bernard Smith—Upper Keuper, East Nottinghamshire. 305 
similar to the last, but in which the quartz-grains are of more uneven 
size. The lamine of the ripple-marks are in this case due to 
either dolomite or quartz rising to 90 per cent., as compared with 
10 per cent. of the other constituent. Part of the rock is patchy, 
i.e. contains nests of quartz or dolomite in the above proportions. 
The quartz shows strain shadows, and the larger grains (;+mm.) 
contain fluid cavities with gas bubbles. The dolomite granules, 
much smaller than the quartz-grains, are often stained with limonite. 
There are a few accessory minerals of no great importance, such as 
papretite, zircon, sphene, and a pale pleochroic greenish-brown mica. 
The second series commences at from 360 to 370 feet above the 
hee of the Keuper Marls, and consists of thinner and less persistent 
sandstones than those of the lower series. They have a siliceous, 
often banded, appearance, and weather out as rough, slaggy- looking 
pieces of stone, with a brown or blue-black stain due to iron or 
manganese compounds, strikingly different from the paler and cleaner 
fragments of the lower skerries. 
A slice of a wavy-banded specimen shows that the light bands 
(reflected light) consist of quartz with small brightly polarizing 
dolomite granules or rhombs, which make up perhaps 380 per cent. 
of the rock. The remaining 70 per cent. is mostly quartz with 
a little accessory twinned felspar (aoorodiae and anorthoclase). The 
angular quartz-grains (all about ;+; mm. in size) show strain shadows, 
and occasionally pack as a mosaic with little or no dolomite between 
them. Some appear to be cemented together or to be parts of 
a previous quartzite. A little detrital calcite mud may be present, 
and angular cavities in the slice may represent plates of that mineral. 
3. In hand-specimens the third type consists of flaggy and false- 
bedded sandstones, in colour white to bright-red, resembling millet- 
seed sandstones with rather loosely cemented grains. These rocks 
are found some 120 feet below the base of the Rhetic beds, or 
about 580 feet above the base of the Keuper Marls. 
Under the microscope the grains are seen to be of two sizes. The 
larger are often beautifully rounded, and average 4mm. in size; 
the smaller are of similar composition, but more angular, occupying 
the interstices between the first. The majority consist of quartz 
(percentage over 95), with strain shadows and fluid cavities with 
bubbles, and there has sometimes been a secondary growth of silica 
upon the surfaces of the grains. Felspar with fine lamellar twinning 
(? oligoclase), fine quartzites, and quartz-schists are also present. An 
interesting point is the appearance of several grains composed of 
dolomite and quartz, having the appearance of rolled fragments of 
a rock resembling that last described. 
Ripple-marks and Contorted Structures. — These structures are 
commonly found in the lower sandstones, but are not confined to 
them. ‘here seems to be no doubt that the drift-bedding and ripple- 
drift was the result of water-action, one set of ripples “being some- 
times partially destroyed and another laid down in a slightly different 
position (Fig. 1). Occasionally the same slab shows ripples crossing 
a second set at right angles. 
In the first two skerry types the quartz fragments and dolomite 
DECADE VY.—YOL. VII.—NO. VII. 20 
