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



GEOLOGICAL RECONNOISSANCE OF POETO EICO ^ 



By Charles P. Berkey 

 (Presented in abstract before the Academy, 7 December, 1914) 



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" 28 



Corozal limestone 23 



Conglomerates 23 



Tuffs 2ry 



Volcanic flows 26 



Intrusives 26 



Summary 29 



Petrographic range 29 



Depth of decay 34 



Structural features 35 



Igneous structures 36 



Volcanic vent complexes 37 



Folding 38 



Faulting 39 



Large structural groups 41 



Unconformities 41 



Veins 42 



1 Based on Ihe observations and studies of an expedition organized under the joint snp 

 port of the New York Academy of Sciences and the Insular Governnicnl of I'orto Ifico. 

 Manuscript received by the Kditor 1 February, 1015. 



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