ON THE GEOLOGY OF THE NORTH-EASTERN WEST-INDIA ISLANDS. 17 



east of Frcederikstced consist. Some smaller spöts near the coast by La Vallie and east 

 of Christianstced are occupied by the same rock. The clay-slate has a dark, grayish-black 

 colour, is fine-grained and perfectly cleavable. I have nowhere been able to find any 

 trace of organic remains in the slate. The rock is perfectly stratified. The dip is gene- 

 rally verv considerable, sometimes the strata are almost vertical but commonly dip 70° — 80°. 

 Near la Vallée the strata are almost horizontal. The strike and dip are subject to great 

 variations in different spöts and generally very difficult to determine exactly. Near An- 

 naly I have seen strata striking W. N: W. — E. S. E. or nearly W — E. and dipping to 

 the north, near Cotton Grove N. N. E. — S. S. W and dipping E. . S. E., by Christianstced 

 N — S. and dipping to the east. By Cookely Bay in the north side the nearly vertical clay- 

 slate strata strike N. N. W. — S. S. E. Sometimes the clay-slate is transformed to a kind 

 of lydian stone as by the lagoon near Christiansteed, where the rock is penetrated by 

 diabase-dikes. In some spöts in the eastern end of S:t Croix the clay-slate is impregnated 

 with silex. There it is a very härd chert-like rock (hornstein) of grayish colour and 

 emits sparks when struck by the hamrner. In Buck's Island are several varieties of slaty 

 rocks, commonly with much lime and I have seen there a band of grayish limestone with 

 plenty of small grains of epidote. The rocks in BucJcs Island contain some obliteratad 

 rraces of fossils. Grayish compact limestone is found, as far I know, only in ohe spöt, 

 near JuditKs Fancy. The rock is härd, dark-gray and fine-grained. It contains a great 

 number of badly preserved fossils, so altered that I have not been able to find out of 

 what kind they are. 



The tertiary formation covers the flat lowland of the south-western part of the is- 

 land. The formation contains two different groups: the lower, composed of broken pieces 

 of coral, and the upper, a white chalk-like marl. The lower part is seen near Frwderik- 

 stced, where it is broken by several quarries formed for the purpose of obtaining building- 

 stone. It is a porous, white rock, almost entirely composed of casts of corals and shells. 

 The rock contains also many rounded and worn pebbles of slate and metamorphic rocks. 

 The fossil shells occur in the form of casts. 1 have collected casts belonging to the ge- 

 nera Conus, Strombus, Natica, Trochus, Venus and Chama. One east af a Cyprsea has exactly 

 the same size and appearance as the east of C. exanthema L., and some impressions of a 

 Cerithium seem to belong to the still living C. litteratum Born. But some extinct species 

 also seem to occur here, and among them one Bidla closely resembling B. granosa Sow 

 of the miocene strata in S:t Domingo. I have also found the impression of a Turbo, cer- 

 tainly living no longer in the Caribbean Sea and belonging to the same type as T. Coohii 

 Chemn of the Pacific Ocean. Unfortunately I have not yet examined the corals collected, 

 but still think it most likely that the formation is of the miocene age. Above the coral- 

 limestone are thick beds of a soft white marl, mostly without fossils*). Those beds seem 

 to me to be about 200 met. in thickness. The recent formations of the island are partly 

 terrestrial, partly marins. The former covers a great deal of the surface of the island in 

 the plains below the mountains. It consists of detritus and clay, sometimes mixed with 



') Near Marys Fancy I have found some fragments of spicula of echinodt rms and pieces of sea-shells. 



3 



K. Vet.-Akad. Handl. B. 9. N:o 12. 



