HILL: GEOLOGY OF JAMAICA. 57 



Minho Beds. 



Metamorphosed conglonlerate " of subsequent date to that of the 

 Cretaceous limestone," composed of ''various crystalline rocks embed- 

 ded firmly in a hard crystalline base ; the whole is of a greenish color " 

 (Tuff?). 



The Richmond formation outcrops in many places a short distance 

 back of the sea along the north coasts of the parishes of St. Aim and 

 Trolawney. It is well exposed beneath the Cambridge beds south of 

 Cambridge along the highway on the west side of Great River, as seen 

 by the writer. It also occurs on the south side of the Blue Mountain 

 Ridge in St. Andrews and St. Thomas. According to Sawkins,^ in the 

 latter parish at Blue Mountain Valley it consists of " alternate bands of 

 red clay, yellow sandstone and light gray shales, 1,000 to 1,200 feet in 

 thickness." 



In general, this formation underlies nearly all the later rocks, and, in 

 our opinion, prior to the Montpelier subsidence it occupied an area 

 as large or larger than that of the island of to-day. 



From data presented in the paleontological chapter of this work, the 

 age of these beds is undoubtedly old Eocene, although it is impossible 

 to draw an exact line between these beds and those of the low^r division 

 which we have termed Cretaceous, and they are no doubt stratigraphi- 

 cally continuous. 



The tmiform alternations of the Richmond beds indicate that they 

 were rapidly deposited over a considerable sliallow area of deposition ; 

 since much of this area was the present locus of the island, it is difficult 

 to infer the situation of the near-by land from which the material was 

 derived ; some of it may have come from the old nucleus of Blue Moun- 

 tain Ridge, but in our opinion this was not of sufficient size to afford 

 all the material. These facts, together with the presence of foreign 

 material, are at least strongly suggestive of the occurrence of land areas 

 during this epoch, concerning the locality of which present knowledge 

 is wholly wanting. 



The Cambridge Formation. 



The beds are named after the typical locality of their occurrence at 

 Cambridge, between Ipswich and Montpelier, in the parish of St. 

 James, in the northwestern portion of the island, near the junction of 

 the boundaries of St. James, Hanover, and Westmoreland. 



1 Jamaican Reports, p. 105. 



