800 INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



represent a series of fringing formations extending around the older plateau region. These in 

 turn are bordered by still later and lower-lying formations. 



Along the south coast of the east end of the island, between Morant Bay and Port Morant, 

 there is an extensive occurrence of gravel beds less than 50 feet in thickness, containing rolled 

 specimens of nearly every species of volcanic rock found in the island, which grades upward into 

 an impure stratified brown and buff colored marl, the latter having a thickness of 200 feet 

 as measured in the bluff upon which Capt. Baker's house at Port Morant stands. The loose 

 gravels at the base of this section have a very recent appearance, a deception which is further 

 aided by the fact that they occur at beach level and contain perfectly preserved fossils resembling 

 modern shells. The fossils heretofore reported from Bowden are found in the gravel bed and, 

 less abundantly, in a few feet of the lower part of the overlying marls, at the foot of the hill, 

 at the beginning of the road leading up the hUl to Capt. Baker's, and in such abundance that as 

 many as 400 species of moUusks have been determined by Dr. Dali from two barrels of material 

 collected by Messrs. J. B. Henderson, jr., and C. T. Simpson, and the writer. A few specimens 

 occur higher up the hUl, whUe near the summit there is a body of firm crystalline secondary 

 limestone containing molds of the characteristic fauna. The physical characters of this forma- 

 tion can be traced from Bowden to Morant Bay and beyond nearly to Yallahs Island, but 

 there it loses its identity. On the road from Bath to Bowden its position above the Cambridge 

 beds is fairly well revealed. 



The stratigraphy of the formation has not hitherto been presented correctly, although in the 

 Jamaican reports under the name of the "Yellow limestone" it was partially confused with the 

 entirely different beds herein described as the Cambridge formation, and the gravel beds were 

 mapped with the Pleistocene and Recent formations. Hence its identity as a formation did 

 not appear in these reports. 



It is only on the south coast of the east end of the island that the Bowden beds have the 

 characters mentioned. It is evident that the formation with modified lithologic features 

 occurs elsewhere on the island, for the Bowden fossils have been found on the opposite side 

 by us and reported from round the district of Vere, near the coast of Clarendon, by other writers, 

 in formations of quite a modified lithologic nature. Probably the Buff Bay, May Pen, and 

 Poms formations, next to be described, are alKed and synchronous deposits. 



For details of the several related formations named, see the report cited. 



The Manchioneal formation is of marine origin and is composed of alternating 

 layers of loose yellow marl and lumpy white limestone with well-defined bedding 

 planes, and locally of alternating evenly bedded marl and impure limestones. 

 Hill describes exposures that exhibit from 100 to 200 feet of deposits of this char- 

 acter. Fossils are not numerous and the occurrences appear to be of small area. 

 Hill «^^ says: 



From the low position of the Manchioneal formation adjacent to the coast and uncon- 

 formably against the older and more disturbed white limestones, it is evident that it was a 

 marginal fringing deposit. Its stratigraphic position above the Bowden formation and below 

 the undoubted elevated reef rock, as well as the paleontologic evidence of its pteropods and 

 Brachiopoda, indicates the Pliocene age of this formation. The contained corals, here poorly 

 developed but occurring iri increased proportions in the succeeding beds, mark the first definite 

 appearance of the marine reef-building species in the Jamaican sequence. 



The Kingston formation is described as consisting mainly if not entirely of 

 material derived from adjacent uplands of the mountains and plateau. It varies in 

 composition, being mostly detritus of the Blue Mountain series to the east of the Rio 

 Cobre and largely white limestone debris to the west of that stream. It has been 



