2 ANNALS XEW YORK ACADEMY OF SCIENCES 



Page 



Minor structures 43 



Enterolithic stnictures 43 



Double cross-bedding 43 



Special relief features 47 



Playas 47 



Promontories ...•". 47 



Terraces 48 



Cuestas 49 



Peneplain 50 



Haystack hiUs 51 



Mineral resources 53 



Gold 54 



Copper 55 



Zinc, lead and silver 55 



Iron — 55 



Coal and oil 56 



Limerock 56 



Guano 57 



Road metal 57 



Hot springs - 57 



Historical statement ^ 58 



Future problems 61 



Base map <■ 61 



Geologic map 62 



District studies 62 



Reef-building organisms 63 



Paleontology 64 



Tertiary subdivision 64 



San Juan formation 64 



Subdivision of pre-Tertiary complex 64 



Mineral resources 64 



Petrography 65 



Physiography 65 



Thermal waters 65 



Geologic history 66 



Collections 66 



Illustrations 67 



Cross-sections 67 



Maps 68 



Acknowledgments 68 



Bibliograpli y 69 



Introduction 



The Island of Porto Eico has never had a thorough or detailed geo- 

 logical study. There have been, however, a number of papers written 

 that have described special features or general conditions in a very ac- 



