442 J. C. Mansel-Pleydell — Geology of Dorset. 



Upper Greensand, but here and there it is concealed by newer 

 deposits ; it has a dip varying from 10° to 90°. At Balh\rd Down 

 the Chalk is vertical, the horizontal strata being suddenly turned 

 upwards into a curve, which is easily traced by the layers of flints 

 with which it is interspersed ; this arises from a fault the evidence 

 of which is seen in its greatest intensity and force at Cocknowle and 

 again east of Corfe Castle. The Upper Chalk (whose characteristic 

 fossils are RhyncJionella octopUcata, Sow., Lima spinosa, Sow., and 

 Marsnpites Milleri, Mant.) prevails on the northern side of the range 

 meeting the Tertiaries at a very low angle, dipping gently to the 

 north-east beneath overlying sands and clays. The Lower Chalk is 

 v^^ell exposed at Houghton and Hilton, where the beds are much 

 disturbed ; they contain several species of Inoceramus and the 

 Brachiopod BJiynchonella Cimeri. 



Tertiary Series. — Lower Eocene. — The lowest of this series, the 

 Thanet Sands, are absent in Dorsetshire, and they do not appear far 

 to the west of London. The Woolwich and Eeading Beds, the next 

 in succession (with the exception of two isolated spots in the neigh- 

 bourhood of Blackdown and Bincombe), do not appear west of 

 Knighton. They are composed of sands, pebble-beds, and clays, 

 accompanied in some places at the base with green-coated flints, 

 which may be favourably seen at Studland Bay and ia a pit near 

 Pamphill, Wimborne; a small section of light-red mottled clays 

 and pebble-beds over the Chalk occurs at Lulworth Park. At 

 Crendle Common near Cranborne is a red -mottled plastic clay, ex- 

 tensively used for pottery of a coarse character. At Chalbury Hill 

 near Horton are pale-grey mottled clays, with an overlying bed of 

 flint pebbles; at East Bloxworth this series is represented by a 

 pale-grey sandy pipe-clay, containing leaves of plants. From the 

 neighbourhood of Cranborne to Wimborne and Bere Eegis it overlies 

 the Chalk with a discontinuous broken margin ; at Tincleton a narrow 

 isthmus of Chalk intervenes, and the Poole Tertiary basin is its 

 utmost western boundary at Yellowham. The alluvial valley of the 

 Erome divides it at Lewell, and, after making a curve through West 

 Knighton, where the mottled clays almost disappear and are replaced 

 by coarse sands, irregular pebble-beds, and whitish clays, it reaches 

 the southern margin of the Poole basin near Broadmayne, and at 

 Littlemayne the Chalk is overlaid by sands which in one place are 

 concreted into large blocks of sandstone, the ordinary Druid Stone ; 

 it flanks the south side of the Poole basin from Warmwell, Winfrith, 

 and Wool, where it takes a southerly direction to Lulworth, and 

 joins the Purbeck range at Whiteway, which commences about a 

 mile north of Durdle Door, extending to Studland ; it follows with- 

 out interruption the northern base of the Chalk range at West Lul- 

 worth ; there are small outliers also at Milborne St. Andrew, Came, 

 Bincombe, Bradford Peverell, and the lofty Blackdown. The Wool- 

 wich and Eeading Beds form a salient feature in the landscape, 

 owing to the prevalence of oak, which grows freer and better upon 

 them than on the strata above or below ; their line of demarcation 

 may be at once recognized by this peculiarity. 



