Vol. 58. ] A DEEP BORING AT LYME REGIS. 283 
sandy, extends as far as Seaton Hole, where it is faulted against the 
Selbornian Sands. The great syncline of Beer Head carries the Trias 
far below sea-level; but the red marls appear again near Branscombe 
Mouth, and rise gradually westward, lower beds successively emerging 
from the shore into the cliff as one travels in that direction. Fine 
sections of the lower beds can be seen by walking along the shore 
at the base of Weston, Dunscombe, and Salcombe Cliffs: the beds. 
under the first two consisting of red marls, with veins and layers of 
gypsum, which is sometimes white and sometimes pink. 
The lower beds of the Keuper Series have been described by the 
Rey. A. Irving, from whose accounts! the following appears to be 
the vertical succession east of Sidmouth :— 
Feet. 
Red and green gypsiferous marls ...................4. seen for 150 
Pale-grey sandy marl; a continuous bed .................006 2 
. Hard, splintery, red marls, with many calcareous con- 
eretions (potato-stones) and thin beds of grey sandstone 
PPM ECE VONS arin Mien sc cen dtu chases cuore eas sha phrase paseeecoke 150 
Massive beds of grey sandstone, with subordinate beds of 
KEG ATO VthICO VCE MAT 0, 2505s ns. taete ss ot siege dace St to cee: 60 
Coarse grey sandstone, with strong current-bedding......... 13 
dete CAICACOMSPIOCCIA, 92.0... c0o5.- ene eceecpidess Seeskecounsinnses 2 
It is a question whether the marls with thin beds of sandstone 
should be grouped with the Keuper Marls, or with the Keuper 
Sandstones. Dr. Irving does not venture an opinion ; but, for the 
purposes of this paper, it will be convenient to class them with the 
Marls, leaving the Sandstone Group a thickness of only 75 feet. 
With regard to the total thickness of the Keuper Marls above 
the Sandstone Group, no exact measurements are possible along the 
coast, because of the frequent landslips in the Weston and Brans- 
combe Cliffs, as well as the Beer syncline and the fault at Whitecliff. 
The distance from Sidmouth to the point where the red marls pass 
below the Rheetic Beds is about 8 miles; and in 1876 Mr. Ussher 
made a rough estimate of the thickness by allowing a deduction of 
3 miles for the Beer syncline, and assuming a constant dip of 3° for 
the remaining 5 miles. This gives a thickness of 1350 feet; but 
he considered that to be an outside estimate, and expressly says that 
inland the marls are not more than 1000 feet thick. 
The objections to Mr. Ussher’s method are that the dip is not 
constant, and that his allowance for the Beer syncline is altogether 
arbitrary. It has occurred to me that another method might be 
feasible; for, if the difference between the dip of the marls and that 
of the overlying Greensand could be ascertained, we might well 
assume that the dip of the marls prior to the deposition of the 
Cretaceous Series was fairly constant for the whole distance of 
Smiles. Thus, if the dip from the basal Cretaceous plane was 13°, . 
the thickness of the marls would come out at nearly 1100 feet; and 
if the dip was 2°, their thickness would amount to 1478 feet. We 
shall see in the sequel that it is certainly more than 1100 feet. 
‘ See Quart. Journ. Geol. Soc. vol. xliv (1888) p. 149, & vol. xlviii (1892) 
p- 68. 
