530 



Dr. J. W. Gregory — Geology of Socotra, etc. 



During last winter Socotra and the neighbouring island of Abd-el- 

 Kuri were visited hy Dr. H. 0. Forbes and Mr. Ogilvie Grant, who 

 made a collection of rocks, upon wliich I have been asked to report. 

 Dr. Forbes has given me an account of the mode of occurrence and 

 distribution of the principal rocks. At about the same time both 

 islands were visited by the Austrian South Arabian Expedition in 

 the " Gottfried," and a note on their geology has been published by 

 Dr. F. Kossmat, in which he remarks the occurrence of Cenomanian 

 and Eocene limestones.^ 



Jfas Hatclaf 



NORTH. 



Hadibo 



or 



Tamri 



SOUTH. 



R.hvolite 



Limestone Series 



Felsile ^ Basalt: 

 Dukes 



Geological Sketch Map of North-Central Socotra. 



Archearv Ser'ies 

 & Grcxnite 



The present collection does not necessitate any modification in the 

 geological history of Socotra, as deciphered by Professor Bonney 

 from the materials available in 1883. But the collection adds to the 

 knowledge of the distribution of the different rocks in the island. 



1. SOCOTKA. 



The rock collection from Socotra contains representatives of three 

 groups of rocks — a basal Archean series, some massive limestones, 

 and some comparatively recent volcanic rocks. 



The largest part of the collection consists of Archean rooks and 

 some associated granites. As a rule the gneiss is more granitoid 



1 F. Kossmat : Sitz. math. nat. CI. k. Akad. "Wiss. Wien, 1899, No. ix, pp. 73-82. 



