82 



M.K. HOWARTH 



Haven at the south-eastern end of the bay as the Global Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage 

 (ie. the world standard definition), is supported by the sequence of ammonites across the Sinemurian/Pliensbachian boundary. All 

 previously figured ammonites from Robin Hood's Bay are listed in a systematic section that includes the evidence on which the 

 ammonite identifications in the paper are based, and 56 of the best preserved ammonites are figured. Eparietites bairstowi sp. nov. 

 is proposed for an early species of Eparietites and a Sowerby Collection ammonite from the Aplanatum Subzone, Raricostatum 

 Zone, in the bay. is designated neotype of Eoderoceras armatum (J. Sowerby). 



INTRODUCTION 



The geology of Robin Hood's Bay (Fig. 1 ) has received the attention 

 of many geologists since the 1820s. One such geologist was Leslie 

 Bairstow, who decided to make the description of the outcrops of the 

 Lower Lias on the foreshore of the bay (Fig. 2) the main scientific 

 work of his life. He started serious investigations in 1 928 and worked 

 in the bay for the next 50 years. Dr L.F. Spath, a colleague at the 

 British Museum (Natural History) (now the Natural History Museum, 

 London), identified the many ammonites that he collected and 

 brought to the Museum. As long ago as 1956 Spath (1956: 147) 

 referred to 'the (still undescri bed) collections made by MrL. Bairstow 

 in Robin Hood's Bay', but Bairstow was never able to finish a 

 detailed account for publication, and finally he left his work for me 

 to complete. That completion has involved more fundamental work 

 than mere editing: complete rewriting of the stratigraphical section, 

 revision of the maps, preparation of many tables and diagrams not 

 envisaged by Bairstow, and revision of the determinations in order to 

 produce an up-to-date account of the ammonites and the 

 biostratigraphy, were all found to be necessary. The final result is 

 eminently worth publishing, if only because it would be very diffi- 

 cult to duplicate the ammonite collection, which is the core of the 

 paper and the biostratigraphy, at the present time. I had many 



Fig. 1 Map showing the location of Robin Hood's Bay on the north-east 

 coast of England, 10 km south-east of Whitby. 



conversations with Bairstow during the period 1956 to 1965,andless 

 frequently up to the early 1980s, and quotations from a few of them 

 are given here. This paper is not the same as Bairstow would have 

 written - his account would have had more local details of the 

 outcrops in the bay as they were in the 1920s and 1930s, while the 

 paper now presented is more orientated towards correlation by 

 ammonites, for which his accurately documented sequence in the 

 bay is of major international importance. The comparison that it will 

 afford with rocks of the same age and the sequence of zones and 

 subzones on the Dorset coast is long overdue. Such comparison is 

 too lengthy to be included here - it would involve much collation and 

 reidentification of the many separate collections of Dorset ammo- 

 nites that now exist, in order to produce a consistent set of 

 determinations, and hence biostratigraphy, that could be compared 

 with the sequence in Yorkshire. 



The term Lower Lias is used in the title of this paper and elsewhere 

 as an exact equivalent of Hettangian + Sinemurian + Lower 

 Pliensbachian. This is the sense in which it was widely used and 

 understood by palaeontologists when Bairstow worked in the 1920s 

 and 1930s. Even in those days a different usage by those geologists 

 more interested in lithology and sedimentation led to confusion on 

 occasions: the boundary between Lower and Middle Lias was placed 

 by them at a position that best marked the change from dominantly 

 clayey beds below to dominantly sandy beds above. Such a change in 

 lithology occurs at different horizons in different parts of Britain, so 

 their usage of Lower and Middle Lias did not have an accurate date 

 or age connotation. So much confusion resulted from these disparate 

 usages that the terms are rarely used now-a-days. Lower Lias is 

 retained here, in the sense given above, in deference to Bairstow and 

 the long history of Robin Hood's Bay geology, where it is well 

 understood as being the Sinemurian + Lower Pliensbachian, there 

 being no Hettangian exposed in the bay. In this usage the Middle Lias 

 is exactly equivalent to the Upper Pliensbachian, and the Upper Lias 

 to the Toarcian. 



LESLIE BAIRSTOW 



Biography 



Leslie Bairstow (Fig. 3) was born in Halifax, Yorkshire, on 14 August 

 1907. After attending Ack worth School (1918-22) and Bootham 

 School, York (1922-25), he went to King's College, Cambridge, 

 where he obtained a degree in Geology in 1928. He started research 

 on the Lower Lias of Robin Hood's Bay in the summer of 1928, 

 supported by college scholarships. He had become interested in 

 collecting fossils from the Yorkshire Lias during his school and 

 undergraduate years, and in getting his ammonites identified he 

 came into contact with Dr L.F. Spath at the British Museum (Natural 

 History). It was at Spath's suggestion that he decided to undertake 

 serious research on the Lower Lias of Robin Hood's Bay, and 

 Dr W.D. Lang, also at the Museum, was keen to get another Lower 

 Lias section accurately documented for comparison with his own 

 work on the Lower Lias of Dorset. He also consulted S.S. Buckman, 

 who advised him to record the location of every ammonite he 



