B. Hohson — A Displaced Mass of Chalk. 257 



(2) It might be held to be thrown down by a normal fault 

 against the Red Chalk seen 3 or 4 yards to south of it. The only 

 fault shown on the Geological Survey Map, 95 S.E. (published 1881), 

 is one with an east and west strike by which the main mass of the 

 Chalk, north of the village of Speeton, is thrown down on the south 

 against the Speeton Clay. Mr. Fox-Strangways ^ remarks : " The 

 junction of the Chalk with the underlying clays is very obscure 

 towards its eastern end ; below Speeton and Reighton we have repre- 

 sented the junction by an uncertain line of fault, the principal 

 evidence for which is obtained in the stream running down to the 

 sea below the former village, where there are beds of red and white 

 chalk resting against the thrown up and disturbed Neocomian Clays. 

 There is a great undercliff of Chalk at this point, vphich much 

 obscures the section, and which might cause the irregularity ob- 

 served in the beck." Lamplugh- remarks: "I think the supposed 

 indications of a fault may be better explained by an ancient 

 foundering of the chalk escarpment, possibly in pre-Glacial times." 

 No white chalk is shown on the Geological Survey map to the north 

 of the Red Chalk. Though the shore reef described in the present 

 note would be more interesting if due to a fault, or (thirdly) to 

 a thrust-plane, such as that described by Dr. Rowe ^ as occurring 

 west of Kit Pape's Spot (to south-east of the reef), the most 

 probable explanation of the present position of the reef appears 

 to me to be the following :— - 



(4) At some former time when the vertical Chalk cliff near 

 this spot had not been eroded so far back (southwards), the line 

 of cliff lay almost along the present line of junction between the 

 Red Chalk of the beach and the white chalk of the reef. A slip 

 took place by which the white chalk on the north side of the plane 

 of slip was thrown down against the Red Chalk, and subsequent 

 marine erosion has exposed both on the shore. Such a slip in the 

 existing cliff occurs at Crowe's Shoot, of which Lamplugh * writes : 

 "There is a huge slip about midway in the Speeton range known as 

 Crowe's Shoot. At this place a great slice of chalk 150 yards long 

 has moved forward and downward for 50 or 60 feet, but has there 

 been arrested, and has remained without further change for over 

 a generation." 



It should be added that the comparatively high angle of dip of 

 the chalk in the shore reef and the inconstancy in its amount and 

 direction favour the explanation above given. 



^ C. Fox-Strangways, "The Geology of the Oolitic and Cretaceous Rocks South 

 of Scarborough" : Geol. Surv. Mem., 1880, p. 38, and 2nd ed., 1904, p. 89. 



2 See p. 256. 



3 Dr. A. W. Eowe, "The Zones of the "White Chalk of the English Coast. 

 Part iv: Yorkshire " : Proc. Geol. Assoc, vol. xviii (1904), p. 202. 



* G. W. Lamplugh, "Notes on the White Chalk of Yorkshire": Proc. York 

 Geol. and Polj-t. Soc, vol. xiii (1896), pt. 2, p. 175. 



DECADE V. VOL. H. — NO. VI. 17 



