254 W. M. Gabh on the Geology of Santa Domingo. 



fossils, usually poorly preserved. I succeeded in obtaining a 

 little Ammonite, a Trigonia, a Pterocardia shell, besides a few 

 less cbaracteristic genera, and wbat may prove to heaBacuUie!; 

 thus fixing the secondary and possibly the Cretaceous age of 

 the oldest stratified rocks on the island. 



These rocks form a border to the crystalline cone, and ex- 

 tend to the eastern end of the island forming its "back- 

 bone." On the borders of the syenite, it is often cut by veins 

 of auriferous quartz, and elsewhere it contams unimportant 



I of San Cristobel, twenty miles west of 



deposits ot copper, ana m one locality, 



In the neighborhood of San Cristot.., ^ 



Sta. Domingo, and extending as far west as we have explored, 

 are small isolated basins of the next formation. This obtams 

 its greatest development on the north side, but is said also to 

 fill a depression extending to Port au Prince. I refer to the 

 Tertiary rocks, which play an important part in the geology of 

 the Island. They lie unconformably on the edges and flanks 

 of the secondary deposits, fill all of the great northern valley 

 of the Citao, and constitute the northern chain. In the northern 

 foot-hills of the central chain, these rocks come in as a thm edge, 

 gradually thickening as we descend into the valley, and eventu- 

 ally acquire a thickness of perhaps 1,500 or 2,000 feet. They 

 consist of conglomerates, sandstones, gray, blue, brown and 

 white shales, argillaceous and pure limestones, the rocks being 

 enumerated in an ascending series from the conglomerates 

 upward Fossils are found throughout the series, thougn 

 usually rare except in the blue and brown shales where they 

 are sometimes very abundant, and in an extraordinarily beauU- 

 ful state of preservation. There have been enough lossns 

 found in all the beds, from base to top, to settle the (juestaon, 

 that no line of demarcation of age can be drawn in the senes. ifl« 

 species have not been sufficiently studied, by me, to enable me 

 to express a positive opinion as to the part of the Tertiary group 

 to which they belong. Messrs. Geo. Sowerby (Qii»";/°"; 

 GeoL Soc, London, 1849, p. 44), and J. Carrick Moore, («oc. t' 

 and Quart. Jour., 1853, p. 129), consider them, for good reasou 

 given, to be Miocene, in which opinion I am inclined toconcu , 

 while Mr. T. A. Conrad, whose acquaintance with the Amenco^ 

 Tertiaries is greater than that of any other person, says ; 

 are Oligocene. ^ j-^irhed 



In the valley of the Cibao these beds are but little chsturo ' 

 at most being but slightly undulated; but in the northern 

 range of mou'ntains they are in some places highty up^^dj 

 one locality being vertical, but were much folded, i" ^^ 

 mines reported to exist in Sta. Domingo are merely tne i}^ 

 lignite in the shales of this group. . , n^art 



It is proper here to call attention to an article in fl\^^. 

 Jour. G^l. Soc. 1853, p. 116, et seq. by a Mr. T. S. Heneken, m 



