LOWER LIAS OF ROBIN HOOD'S BAY 



93 



Fig. 14 The prominent hard calcified shale of bed 447 in front of Peter White cliff. M.K. Howarth photograph. 10 September 1991. 



lowest bed of the Lower Pliensbachian. The most prominent bed on 

 the map is bed 474, Double Band, which forms Billet Scar (see Fig. 

 16). The narrow excavation through beds 476^186 known as The 

 Dock, was originally made for fishing and smuggling purposes. 



GEOLOGICAL STRUCTURE OF ROBIN 

 HOOD'S BAY 



The pattern of the outcrops on the foreshore of the bay as seen in Fig. 

 4 is determined by the structure of the rocks (Fig. 1 7 ) . That structure 

 was first alluded to by Tate & Blake (1876: 27, 196) who described 

 Robin Hood's Bay as 'a complete inlier ... in the form of a mound, 

 dipping in all directions from the centre . . . the centre of elevation 

 beneath the sea, nearly opposite the centre of the bay'. In the 

 Geological Survey memoir, Fox-Strangways & Barrow (1915: 3, 

 115) referred to the Lias as 'curving over in a gentle arch or 

 anticline'. Versey (1939: pi. 15) plotted the contours of the base of 

 the Grey Limestone (=Scarborough Formation; Lower Bajocian) 

 over a wide area and showed that around the southern and western 

 sides of Robin Hood's Bay they formed the outer part of a north-west 

 to south-east elongated dome . According to Versey (1939) the dome 

 was produced by tectonic movements probably in the late Pliocene. 

 Kent (1974: 25, 26) and de Boer (1974: 281) accepted the date of 

 formation of the dome as later than the mid-Tertiary Alpine move- 

 ments and probably Pliocene. 

 The central part of the Robin Hood's Bay dome can be defined by 



the outcrops of the Lower Lias on the foreshore of the bay. Fig. 17 

 shows contours on the outcrop at 10 m bed-thickness intervals, with 

 the m contour starting at the top of bed 422.2, Low Balk. Because 

 the outcrop on the foreshore is essentially flat, the contours approxi- 

 mate closely to strike lines, and they form the pattern of a dome, with 

 a NW to SE axis of elongation in approximately the position shown 

 on the figure. The dip of the beds is at right angles to each contour 

 line away from the centre of the dome. In the northern part of the bay 

 the beds dip NW. and from the 50 m to the 150 m contours the 

 average distance between adjacent contours is 128 m; this gives an 

 average dip of 4.5° for the beds. Between the 20 m and 40 m contours 

 the beds dip to the west, while the lowest beds between the m and 

 20 m contours dip between west and south at an average of 3.2°. In 

 the south-east corner of the bay near the Peak Fault the beds curve 

 round to dip south-easterly. The Peak Fault throws down on its 

 eastern side and has a lateral movement of several kilometres. Its 

 northern continuation across Robin Hood's Bay, passing close to the 

 shore at the northern end of the bay, is shown on Fig. 1 7 in accord- 

 ance with data on the latest map of the British Geological Survey that 

 includes off-shore geology (British Geological Survey, 1995, Tyne 

 Tees, sheet 54°N-02°W, 1:250,000, solid geology). 



STRATIGRAPHICAL SUCCESSION 



Bairstow drew up a description of the succession in Robin Hood's 

 Bay in 1928-30 and the detailed sequence of beds formed an 



