hill: geology of JAMAICA. 225 



PART VII. 

 APPENDICES. 



I. 



Additional Note on the Geology op Porto Rico and Santiago 



DE Cuba. 



Since the foregoing pages were placed in type I have made a geologi- 

 cal reconnoissance of Porto Rico and Santiago de Cuba. In the former 

 island I found the general Antillean sequence, but modified by certain fea- 

 tures hitherto known only in the Caribbean chain : — 1. An older plexus 

 of water-sorted horublendic volcanic material, — tufifs and conglomerates 

 with interbedded Cretaceous Rudistean limestone similar to that of 

 Jamaica, composing the central mountains. 2. An Eocene system of 

 impure lignitic sands and clays like the Richmond beds, occurring on the 

 western side of the island near San Sebastian. 3. Fossiliferous marl 

 beds overlapping the above, which at this writing have not been deter- 

 mined. 4. Miocene coral limestone, unlike anything hitherto recorded 

 from the Great Antilles, but of the type occurring in Antigua. These 

 constitute the hilly country north and northwest of Lares. 5. White 

 limestones of probable Pliocene age, composing the hills of the south 

 coast. 6. Elevated reefs, but feebly represented. 7. Alluvial plains 

 of Pleistocene age. The terrace phenomena are less developed upon 

 this island than in any of the other Great Antilles, although the Pleisto- 

 cene base-levelling is well developed in stream valley phenomena. Dikes 

 of syenitic-like porphyry, probably dioriteS, were also noted cutting the 

 older hornblendic rocks. 



Evidence was obtained indicating that the greater mountain move- 

 ment culminated before the Miocene, and that there has been at least 

 one thousand feet of vertical uplift since that epoch. 

 VOL. xxxiv. 15 



