Planktonic Foraminifera from the Eocene Navet and San Fernando 

 Formations of Trinidad, B. W. I. 



By Hans M. BoUi ' 



Introduction 



TPhis paper contains the results of a study of plank- 

 ^ tonic Foraminifera and their stratigraphic distribu- 

 tion in the Eocene Navet and San Fernando formations. 

 It represents the link between similar investigations in 

 the Paleocene-lower Eocene Lizard Springs formation 

 and the Oligocene-Miocene Cipero and Lengua forma- 

 tions. Planktonic Foraminifera have been chosen for 

 the biostratigraphic subdivision of the Navet and San 

 Fernando formations on account of their abundance 

 and the short life ranges of many species. The species 

 and subspecies of the genera Hantkenina, Cribrohant- 

 kenina, Chiloguembelina and related genera are omitted 

 because they have previously been described in detail 

 by Bronnimann (1950a, b) and by Beckmann (1957). 

 The stratigraphic distribution of the Chiloguembelinae 

 given by Beckmann is based on the same zonation as is 

 proposed here; that of the Hantkeninae and Cribro- 

 hantkeninae was given in more generalized terms by 

 Bronnimann and a few remarks on how the more char- 

 acteristic species fit into the present zonation are made. 



The smaller Foraminifera of the Navet formation 

 have previously been described by Cushman and Renz 

 (1948). The Orbiilinidae were piu-posely left out by 

 these authors, and of the Globorotaliidae only 4 species 

 were included. The Eamdat marl, which is now placed 

 in the Lizard Springs formation (Bolli, 1957a), was 

 regarded as the basal part of the Navet formation and 

 the Hospital Hill marl, now included in the Navet 

 formation, was treated as a formation of its own. The 

 fauna described by Cushman and Renz was collected 

 from several isolated outcrops in the Central Range and 

 Naparima area of Trinidad, each containing a distinct 

 foraminiferal assemblage based on which the authors 

 proposed a tentative stratigraphic sequence. 



Unlike the Upper Cretaceous formations, the Pale- 

 ocene-lower Eocene Lizard Springs formation, and the 

 Oligocene-Miocene Cipero and Lengua formations, in 

 all of which some comparatively undisturbed siu-face 

 or subsurface sections are known, the Navet and San 

 Fernando formations outcrop only in small, isolated 

 masses in tectonically strongly disturbed areas. At the 



' The TriuldBd Oil Company, Ltd. (ftrmerly Trinidad Leaseholds, Ltd.), Polnte- 

 a-Pierre, Trinidad, B.W.I. 



present time not one reasonably complete surface or 

 subsurface section is known. 



Because of this virtual absence of continuous sections 

 the present investigations had to be confined to isolated 

 outcrops and subsurface samples, altogether about 50 

 in number. This was found to be a great handicap for 

 detailed biostratigraphic and evolutionary studies. Only 

 because many planktonic species have a short life range 

 or show rapid morphological changes during their evo- 

 lution has it been possible to establish the proposed 

 zonation of the middle and upper Eocene of Trinidad. 

 It still remains doubtful whether the zones given here 

 represent a complete sequence of beds. 



Acknowledgments 



The writer is indebted to The Trinidad Oil Company 

 for permission to publish this study and to use the 

 Company's laboratory and drawing ofiice facilities at 

 Pointe-a-Pierre. The publication of this paper has been 

 made possible thi-ough a grant in aid from the Cali- 

 fornia Research Corporation, The Carter Oil Company, 

 The Gulf Oil Corporation, and the Humble Oil and Re- 

 fining Company, made to the Smithsonian Institution 

 for the study of planktonic Foraminifera. 



The author wishes to thank Dr. H. G. Kugler, con- 

 sulting geologist to the Central Mining Investment 

 Corporation and Mr. J. B. Saunders, paleontologist of 

 The Trinidad OU Company, for reading and discussing 

 the manuscript. Dr. K. Rohr kindly made the sketch 

 map showing Navet localities in the Central Range. 

 Through discussions and exchange of material Dr. P. J. 

 Bermudez of the Creole Petroleum Corporation has 

 aided the author in the determination of several species. 

 Thanks are due to Dr. A. R. Loeblich, Jr., of the U. S. 

 National Museum and to Mrs. Helen Tappan Loeblich, 

 Research Associate, Smithsonian Institution, for their 

 help extended in the completion of the paper. 



Mr. R. A. Pallant, senior draftsman of The Trindad 

 Oil Company, supervised the preparation of the table 

 and text figure. The plate illustrations are camera 

 lucida drawings by Patricia and Lawrence Isham, 

 scientific illustrators, U. S. National Museum, Wash- 

 ington, D. C. 



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