540 MESSES. G. F. FRANKS & J. B. HAKEISON [Aug. 1 898, 



33. The GzoBiaEEH^A-M.A.^jjS [and Basal E-eef-eocks] of Eaebados. 

 By G. F. Feanks, Esq., M.A.,E.G.S. and Prof. J. B. Haeeison, 

 M.A., F.G.S. WitJi an Appendix on the Foeaminifeea. By 

 F. Chapman, Esq., A.L.S., F.R.M.S. (Eead June Sth, 1898.) 



Contents. 



Page 



I. Introduction 540 



II. The Orographic and Tectonic Structure of Bissex Hill 541 



III. The Succession at Bissex Hill 545 



IV. Bowman ston and other Localities where similar Eoeks occur 547 



V. Conclusions 548 



VI. Appendix on the Foraminifera 550 



I. Inteodtjction. 



Mention was made of the Globigerina-mails of Bissex Hill in a 

 paper on the Geology of Barbados written by one of us in 

 collaboration with Mr. Jukes-Browne,^ and the section along the road 

 ascending the hill from the south-western side was there described. 

 The ordinary succession of the Oceanic deposits occurs in the lower 

 part of this section for 70 feet vertical, up to an elevation of about 

 865 feet. Here the hill rises somewhat abruptly from a small 

 plateau of the siliceous earths to a knoll at an elevation of 966 feet, 

 falling away to a spur on the east, the ridge of which, to the point 

 where it terminates abruptly, has a level of about 900 feet. On the 

 north the knoll slopes steeply down to a level of 820 feet. On the 

 west, be]ow the road, the land falls away rapidly to Dark Hole and 

 the Yale, the lowest exposure of the Oceanic Beds being north 

 of Park's Windmill, at the height of 670 feet. 



The whole of the crown of Bissex Hill, instead of showing the 

 usual passage from siliceous earths through white chalks into red 

 clays, was found to consist of a yellowish or buff-coloured marl, 

 which proved to be crowded with Globigerince, and to include 

 occasional large blocks and several embedded layers of hard Glohi- 

 (/mna-limestone. In the first instance no change in the character 

 of the deposit was noticed from where it first occurred to the 

 summit of the hill, and it was supposed to be a local deposit taking 

 the place of the usual chalk. 



It was afterwards discovered, however, that the marl forming 

 the base of the knoll on the hilltop on the southern face contained 

 a variety of organic remains, and a slide cut from a sample sent to 

 the authors of the above-mentioned paper revealed the fact that it 

 included small fragments or pebbles of true Barbadian chalk. 

 From this it was concluded that the rock of the knoll was a 

 remanie deposit, formed from the erosion of the underlying Glohi- 

 ^e?^ma-marls and of the neighbouring chalks during the upheaval 

 which culminated in the emergence of the island. It was conse- 

 quently classed with other beds which seemed to be of intermediate 

 age between the Oceanic Series and the coral-rocks. 



^ Quart. Journ. Geol. Soc. vol. xlviii (1892) pp. 170-225. 



