Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/207

 Lower Chalk.

Chalk-rock nodules, at a ledge running out into the shingle-beach.

Chalk without flints.

Chalk Marl, more or less hard.

Upper Greensand. — Green-grey and partly hard. Along the top of the cliff the top part of this is calcareous, and passes up into the Chalk Marl.

At Lulworth Cove the fallen state of the cliff hid much of the accessible part of the section ; but the grey soft layer at or near the top of the Chalk Marl was to be seen.

In Man-of-war Cove I could not see the Chalk-rock at the eastern part, where the junction of the Upper and Lower Chalk seems to be much confused. Westward, however, the nodules of the rock are to be seen up to a height of 5 feet above the beach, when they are cut off by Chalk, again with confused bedding, soon succeeded by Chalk with flints, also somewhat confused. Still further west the nodules again occur, and the Upper Chalk is less than 80 feet from the Upper Greensand, the bedding of which latter and of the Chalk Marl is reversed, being at an angle of about 70° S.S.W. instead of northwards. The Chalk Marl seems at one part to be 45 feet thick. It has the usual darker clayey bed at top, whilst the bottom 2 feet or more contains dark grains, small brown nodules, and grains of quartz. The top part of the Upper Greensand is hard from its large irregular-shaped nodules of chert ; and the topmost 2 feet or more is sometimes a buff cherty sandstone.

At the eastern end of Durdle Cove the dip of the Chalk Marl and the Upper Greensand is still reversed southwards, at an angle of 80°. The former, with its grey soft layer near the top, is succeeded by Chalk with a few flints ; and, indeed, there is one layer of flints less than 20 feet from the Upper Greensand, and therefore in the Chalk Marl, which, however, is here not clearly separable from the Chalk above. A little westward the Chalk with flints comes on ; and the bedding is confused at the bottom of the cliff, as in Man-of-war Cove. On turning the corner, into the deeper part of the Cove, a cream-coloured and partly greenish layer of nodules (like those of the Chalk-rock) may be seen. Beyond this the frequent layers of flint show a southerly or reversed dip of about 65°, soon changing to a higher angle, and afterwards to a curved dip in the other direction, 30° at the top, and 60° or more at the bottom of the cliff, as shown in fig. 1.

Fig. 1. — Section of the Chalk with flints. Eastern side of Durdle Cove.

a. Beach-line. b. Fallen earth. c. Chalk with Flints. d. Nodule-layer.