Geology of the Neighbourhood of fVeT/moufh, Sgc. 9 



composed of beds of the greensand formation ; but these are rendered invi- 

 sible in the greater part of the Weymouth district, in consequence of a fault 

 which runs along the escarpment for nearly ten miles, from Poxwell to Abbots- 

 bury, and brings up strata, subjacent to the greensand, into immediate contact 

 with the chalk : this fault we shall hereafter describe. 



The promontory of White Nore is the last point in the South-west of Eng- 

 land at which the great body of the chalk touches the sea; those insulated por- 

 tions of this formation which occur in the cliffs between Lyme and Sidmouth 

 being only detached outlying masses, separated, by denudations of many miles 

 in width, from the south-west termination of the great chalk basin of Dorset- 

 shire*. 



The mineralogical character and organic remains of the chalk in this 

 district present nothing unusual : the lower strata of the chalk pass into hard 

 chalk, devoid of flints, and interspersed irregularly with green grains of sili- 

 cate of iron. 



Greensand. 



The strata of the greensand formation, which at White Nore emerge 

 from beneath the lowest chalk, dip conformably with it to the north-east, and 

 attain a thickness of about 100 feet : their succession in a descending order 

 is : — 1. Chalky glauconite, composed of greensand interspersed with cal- 

 careous cement. 2. Green, yellow, and brown sand, alternating with irre- 

 gular calcareous concretions, and with thick beds of chert. 3. Dark argil- 

 laceous greensand, with large nodular concretions, equivalent to the sandy 

 concretions called cow-stone, at Lyme Regis : the upper subdivisions of this 

 section also closely resemble some of those exhibited by the greensand for- 

 mation near Lyme. 



We are unable to recognise distinctly in this district, or in any part of the 

 coast west of Weymouth, those regular and extensive threefold subdivisions of 

 fire-stone, gault, and lower greensand, which are so obvious in Hants, Sussex, 

 and Kent; although an approximation to the character of fire-stone may be 

 traced at White Nore, and still more decidedly in Devonshire, in the cliff and 

 quarries of Beer already described by Mr. De la Bechef. 



For a considerable distance near White Nore and Osmington the green- 

 sand is visible at the base of the chalk escarpments, dipping always conform- 

 ably to the chalk; but along the great escarpment from Poxwell to Abbotsbury 

 it is seen only in two places, namely, near Sutton Pointz, and at Bincombe, 

 being elsewhere masked by the Portland stone, which the great fault that 



* See Map, Plate I. f Geological Transactions, Second Series, vol. ii. p. 109. 



VOL. IV. SECOND SERIES. C 



