GEOGRAPHIC FEATURES OE THE TERTIARY PERIOD. 81 



that there was a submergence until the close of the Miocene period. How- 

 ever, the Miocene period was characterized by some important changes of 

 level, for mechanical sediments often replace the calcareous. Several 

 years ago Professor W. 0. Crosby found radiolarian earths at Baracoa, 

 Avhich were identified by Dr J. W. Gregory. These have been regarded 

 as of deep-sea origin. Samples of the earth were kindly given the writer 

 by Professor Agassiz, for whom it had been collected by Mr R. T. Hill. 

 Their occurrence in other islands of the West Indies was better known, 

 and they have been correlated with the Barbadoes deposits of Mr Jukes- 

 Browne.* If these radiolarian earths were deposited concurrently with 

 those of the Barbadoes and the Miocene earths of the Atlantic coast 

 and Jamaica, then it would appear that portions of Cuba were depressed 

 to abysmal depths before or during the earlier Miocene period, for the 

 present writer has found that no radiolarian earths occur in the succeed- 

 ing Pliocene deposits which rest upon the greatly denuded Miocene lime- 

 stones of Cuba. 



Since the above was written Mr Hill has published stratigraphic evi- 

 dence of the Baracoa earths underlying Miocene beds. 



Pliocene History. 



ma ta nza s forma tion. 



In patches or in more continuous belts there are white and stained lime- 

 stones and marls constituting a formation resting unconformably upon 

 the greatly eroded surfaces of the older Tertiary and the Cretaceous strata 

 already described. The more chalky beds become case-hardened upon 

 exposure. The formation contains more or less fragmental material, de- 

 rived from the broken remains of the older Tertiary rocks, and sometimes 

 water- worn pebbles of the same material. Where unconformity is not 

 recognizable there is often difficulty in distinguishing these calcareous 

 beds from the Miocene marly rocks, but the formation is fossiliferous. 



In the Havana region Salterain catalogued the following fossils which 

 he found in this formation : 



Cerithium. Dollium sp. Patella sp. 



Tubes of Gastrochsena. TeUlna sp. Bulla sp. 



Lithodomus. T. planata (?). Dendrarea. 



Lucina tigrina. T. planissima. Heliastrsea. 



L. sp. L. semireticularia. Pecten sp. Meandrina. 



L. quadrisulcata. Cardium sp. Madrepora. 



Area biangula. Crassatella sp. 



•"Geolo2;y of Barbadoes:" Quar. Jour. Geoi. Soc, Lond., 1891, vol. Ixvii, pp. 197-250, and 1892, 

 vol. xlviii, pp. 170-226. 



