506 



C. T. Trechmann- 



The outcrop is included in the most westerly of the several inliers 

 of older rocks that protrude from below the Tertiary White Lime- 

 stone covering of the island. No Cretaceous limestone is mapped by 

 Sawldus in this locality, the spot where the outcrop occurs being 

 indicated as Trappean, bounded on the north and west by White 

 and Yellow Limestones. No mention of Barrettia occurs in the text 

 of Sawkins, and so the limestone outcrop seems to have been over- 

 looked. The Barrettia limestone occupies approximately the 

 northern and north-eastern portion of the outcrop, which Sawkins 

 maps as Trappean, and the Tertiary White Limestone of presumed 

 Oligocene age is clearly faulted down against it along some distance 

 on the north, as I have indicated in a diagrammatic section (Fig. 1). 



It consists of a grey nodular rather massive limestone, which shows 

 stratification and bedding fairly well in places. The first outcrop 

 one encounters on approaching from the sea on the north forms a 

 picturesque wooded and flower-covered ridge, about 200 feet above 

 sea-level. The Barrettia limestone forms an escarpment facing south 

 and strikes about E.N.E. and W.S.W., and is rather lower than the 



N. 



S.;^ 



Fig. 1. — ^Diagrammatic sketch showing position of the Barrettia Limestone near Green Island, 

 Western Jamaica. Length of section about a mile. Height about 300 feet above sea-level. 

 F. fault; O.K. coral rock; W.L. White Limestone (Tertiary); B. Barrettia Limestone; 

 C. " Trappean " conglomerate ; S. grey and red calcareous shales ; Y.S. yellow sandstone^ 

 The shales and sandstones appeared to be unfossiliferous. 



ridge of White Limestone on the north. It dips about 20 degrees 

 to the north and north-east, and has a thickness of 16 or 20 feet. 

 On the opposite side of a small valley to the south, down which a 

 stream runs, the Barrettia limestone crops out again round the 

 edges of a rather higher hill, and forms an escarpment and a small 

 cliff facing north and west. The surface of the limestone here 

 weathers to clay, and is occupied by yam-fields, and the enclosures 

 and stone heaps are largely made up of Barrettia, some of them 

 excellently preserved. Further to the south the limestone seems to 

 be cut off by faults, as the hill opposite the escarpment consists of 

 red Trappean beds. 



Some negro labourers were kindly provided by Mr. Jenoure, 

 and so I had a cutting made down the wooded slope of the valley 

 to ascertain definitely what rock underlay the Barrettia limestone, 

 and found it to consist of a grey, friable, nodular limestone overlying 

 a sandstone. In the bed of the stream grey calcareous shales, locally 

 called " Bruggadoo ", are exposed. This is a negro term given to 

 the rich soil formed from the weathering of shales and marly lime- 

 stones specially suitable for banana growing. 



