2 ANNALS NEW YORK ACADEMY OF SCIENCES 



Page 



• Minor structures 43 



Enterolithic structures 43 



Double cross-bedding 43 



Special relief features 47 



Playas 47 



Promontories 47 



Terraces 48 



Cuestas 49 



Peneplain 50 



Haystack hills 51 



Mineral resources 58 



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 



Bibliography 69 



Introduction 



The Island of Porto Eico has never had a thorouo-h or detailed seo- 

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

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



