[Annals N. Y. Acad. Sci., Vol. XXVI, pp. 1-70, Pll. I-III. 3 March, 1915] 



GEOLOGICAL EECONNOISSANCB OF PORTO RICO ^ 



By Charles P. Berkey 

 {Presented in abstract before the Academy, 7 December, 191Jf) 



CONTENTS 



Page 



Introduction 2 



General description 3 



New York Academy of Sciences Expedition 7 



Object of the expedition 9 



Investigations and discussions 9 



Rock formations 9 



Younger series 11 



San Juan formation 11 



Arecibo formation 12 



Older series 17 



Shales IS 



Limestones 19 



Coamo tuff -limestone 19 



Trujillo Alto limestone 21 



"Shred" limestone 21 



La Muda limestone 22 



"Mountain limestone" 23 



Corozal limestone 23 



Conglomerates 23 



Tuffs 25 



Volcanic flows 26 



Intrusives 26 



Summary 29 



Petrographie range , 29 



Depth of decay 34 



Structural features 35 



Igneous structures 3g 



Volcanic vent complexes 37 



Folding 3g 



Faulting 39 



Large structural groups 41 



Unconformities 44 



Veins 42 



1 Based on the observations and studies of an expedition organized under the joint sup- 

 port of the New York Academy of Sciences and the Insular Government of Porto Rico. 

 Manuscript received by the Editor 1 February, 10] 5. 



(1) 



