720 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The detailed subclassification of the Oceanic series comprises not only the 

 Catadupa and Chapelton beds of the Cambridge formation, but also the Montpelier, 

 Moneague, and Cobre formations. Of the Montpelier Hill**^® says, quoting 

 Charles B. Brown: 



It consists of thin beds of white limestone, interbedded with a soft white chalky marl, the 

 limestone beds invariably containing nodules of flint. The limestones are chiefly soft but sel- 

 dom compact or crystalline; they form thin beds, which vary from a few inches to 4 feet in 

 thickness and are much disturbed, so as to dip in almost every direction over small areas. The 

 marl beds, being interstratified with these, of course show the same disturbance and dips and are 

 similar to them in thickness. The flints and chert contained in the limestone beds lie usually 

 in flattened nodular masses in lines of stratification and are rarely in beds themselves. They 

 are not connected continuously but are in long, hollow flat masses, and have all the appearances 

 of having been deposited around or in the substance of some organic form which was embedded 

 in the limestone. These flints are chiefly of brownish-pink, brown, and gray colors. At Knock- 

 alva and other places in the vicinity the limestone contains small veins of silica, and also has 

 become so thoroughly impregnated with that substance as to be completely changed into a 

 siliceous limestone." 



Microscopic examinations show that the calcareous beds consist of organic oceanic material 

 and are composed of the sheUs of Foraminifera, occasional sponge spicules, and fine Crystals and 

 amorphous particles of carbonate of lime, like those usually found in all chalky oceanic deposits. 

 No terrigenous material whatever has been found in any specimens examined. The Montpelier 

 beds are singularly free from molluscan or other visible fossils, except a large species of Orbitoides 

 in its lower beds. Nummulinse have also been found. * * * 



The thickness of the Montpelier formation is difficult to determine, owing to lack of continu- 

 ous exposures. Our observations have led to the conclusion that they do not exceed 1,000 feet. 

 Everywhere these beds show great disturbance, but not to the degree of the Blue Mountain 

 series, usually consisting of more open folds. 



The Montpelier beds are the deepest sediments preserved in the geological structure of 

 Jamaica and represent the culmination of the great subsidence initiated in the Cambridge 

 epoch. Judging from the rapid transition between the littoral Cambridge formations and the 

 chalks of the Montpelier formation, this subsidence must have been rapid in geologic time. 



The age of the Montpelier beds most probably, corresponds to that of the late Eocene (old 

 classification) now called the early Oligocene, agreeing approximately with the position of the 

 Vicksburg stage of our American Tertiary. This inference is based upon the position of the 

 beds above the undoubted lower Eocene of the Cambridge formation and below the undoubted 

 late Oligocene of the Bowden formation, together with the occurrence of Orbitoides manteUi. 



In regard to the Moneague formation Hill *^'' states: 



The Montpelier beds grade up into more massive limestones, white in color, firmer in texture, 

 often semicrystaUine, sometimes containing casts of fossil mpUusks and solitary corals, and 

 occurring in well-defined bands of stratification from 1 to 5 feet in thickness. More massive 

 texture and regular bedding especially distinguish this formation from the other white lime- 

 stones of the island, such as the chalky rocks of the underlying Montpelier and the irregular 

 lumpy texture of the overlying Cobre formations. These rocks contain many cavernous molds 

 of Mollusca and single coBals, indicating that a considerable amount of shell debris may have 

 accompanied their original deposition. The fossils obtained near Ewarton, Retreat, and Cinna- 

 mon HQl, in a firm limestone matrix, were mostly poorly preserved molds of corals and mollusks, 

 which the paleontologists could not determine. * * * 



<^ The description above given refers to Brown's lower division of the white limestone (our Montpelier beds); the 

 upper beds (our Brownstown bedo) are more compact and massive and contain fewer interstratified marls. 



