Geuhjjiii of Norllicdstcni West India hlaiids. 185 



XII. — Outliiie of the Geuluyy of the Nortltmsierii. We^l India 



li^hoids. 



BY p. T. CLEVE, 

 Op the University of Upsala, Sweden; Corresponding Member, N. Y. A. S. 



Read November 7th, 1881. 



In the winter of 1868-G9 I made a geological survey of tlio 

 northeastern corner of tlie AVest Indian Archipelago. The re- 

 sults obtained Avere published in the Transactions of the Eoyal 

 Swedish Academy of Sciences of Stockholm (T. IX, No. 12, 

 1871), with some geological maps of the islands surveyed. 

 Considering .that the many details, which are gathered in this 

 paper, may prevent the reader from getting a clear idea of the 

 geology of this interesting part of the globe, and that the paper 

 may not be easily accessible to American readers, I have acceded 

 to the wishes of my respected friend, Mr. Thomas Bland, and 

 written a short outline of the most important facts found by 

 myself, and compared them with observations made by other 

 geologists in other ]iarts of the West Indies. 



The geological ages in which the material forming the islands 

 was deposited, or protruded from the interior, are the Cretaceous, 

 the Eocene, the Miocene, Pliocene and Post-]iliocene. 



The Cketaceous Fokmation" forms the whole of the archi- 

 pelago of the Virgin Islands except Anegada, Avhicli may be re- 

 ferred, as also the Bahamas, to the Post-pliocene time. Also the 

 island of Yieque, near Porto Rico, seems to consist for the most 

 part of eruptive Cretaceous rocks. Still, there seem to be also in 

 this island younger strata; but I cannot say anything with confi- 

 dence about this, having paid only a short visit on this island. 



A map of the Virgin Group shows a series of larger islands 

 and smaller keys, extending generally east and west. The larger 

 are Culebra, St. Thomas, St. John, Tortola and Virgin Gorda. 

 Their general direction coincides with the strike of the strata, 

 wherever such is visible. South of these, but at some dis- 



