W. IT. Hndlesfon — Creechbarrow in Piirhcck. 



255 



elevation of 500 feet, whereas the Lower Tertiaries along the dip 

 slope of the Pnrbeck Hill elsewhere rarely attain an elevation of 

 300 feet (see Fijj;. 1 for confirmation of this). Hence, the a,2;ency 

 which protected the Creechbarrow Beds protected the Lower Tertiaries 

 to a certain extent. I cannot doubt that this agency was the hard 

 concretionary limestone which now constitutes the summit of Creech- 

 barrow itself, and which in all probability extended considerably 

 further in a direction opposite to the dip after the manner of 

 escarpments generally. 



Summit ot 

 Creechbarrow 



Parbeck 

 Hill 



N.N.E 



s.s.w. 



Fig. 4. — Geueralized section of Creechbarrow (south side). 

 a-d. CreechbarroAV Beds. a. The hill-top limestone, b. Sands with calcareous 

 concretions. <$- Bed of flints, c. Sands below the flint-bed. d. Beds not 

 specially determined, mostly sandy. (See section-pac^e.) 



i'^. London Clay. i". Reading- Beds. h°. Chalk. 



Whether the Creechbarrow Beds are really unconformable to the 

 Lower Tertiaries, as shown in the diagram, I am unable to say. 

 Also the angle of dip of these beds is only obtained by inference. 

 The high dip of the Lower Tertiaries shown in the diagram is 

 based on the three following considerations : (1) on the narrowness 

 of the outcrop, (2) on a dip of 80'^ towards the north which is seen 

 in the adjacent chalk-pit, and (3) on the fact that one of the 

 ironstone-gTits of the Eeading Beds is seen in a vertical position 

 about f mile to the eastward of the section. With reference to the 

 Creechbarrow Beds themselves, a dip of from 10° to 12° is obtained 

 from observation for the topmost series,^ but the actual dip of the 

 lower beds, in immediate contact with the London Clay, as also 

 their true stratigraphical relations, can only be a matter of inference. 



The primary object of this investigation has been an endeavour 

 to explain the causes which have led to the formation of such 

 an exceptional feature in the landscape of the Isle of Purbeck 

 as Creechbarrow, certainly the most noteworthy hill composed 



1 See p. 248. 



