Is more concerted effort possible in establishing the regional significance of planktonic foraminifera as indices of geologic age?

R. M. Stainforth
The Micropaleontologist 1950 – 4:1:18

I believe that planktonic foraminifera could be made the basis for very precise regional, inter-regional and even world-wide correlations. Their mode of life gives their fossil remains an age-significance unaffected by the problems of homeotopy and heterotopy which reduce the value of benthonic microfaunas in long-range correlation. My personal experience in several countries, supplemented by the available literature, convinces me that there Is an important field for research here, yet it seems to be receiving little attention. With the exception of an occasional paper such as LeRoy’s on the mid-Tertiary “Orbulina-surface”, the Globigerinidae tend to be underrated and even Ignored in faunal and biostratigraphic papers. The late Dr. Cushman excluded the family from most of his later papers, pending a revision of their classification, *owing to the chaotic condition of the species in the literature (letter of September 26, 1949).

I think it should be possible to co-ordinate our efforts better and thus determine the geographic spread of extinct planktonic microfaunas and the degree to which the succession of species remains constant over long distances. There is evidence from the literature that some concrete results will emerge, witness Thalmann’s records of the evolution of Hantkenina in the Eocene and records of Globorotalia (Turborotalia) of the cocoaensis tribe becoming extinct at the end of the Eocene. It is equally certain that anomalies will arise, such as the extinction of Globigerina concinna early in the Caribbean Oligocene, yet its persistence into the younger Tertiaries of the Middle East. For the present we can only speculate on past migration, interoceanic barriers and currents, temperature zones, etc., but analytic methods could be applied to solving these problems if sufficient factual data were at hand.

These brief remarks form a plea to all students of foraminifera, and especially to those who have tended to Ignore the Globigerinidae, to pay due attention to the planktonic forms and to make known the order of advent and extinction of species in different parts of the world.

The main item of news from Peru is that Benton Stone has left the International Petroleum Company to supervise micropaleontological work of the Standard-Vacuum Company in Sumatra. Before leaving he completed manuscripts on the rich microfaunas of the Upper Cretaceous Redondo formation (“Clavulina” shale of some authors) and the Eocene Talara shale. When these are published the whole Tertiary column of northwest Peru will be covered in the literature excepting the Lower Eocene Pala Greda formation and the Oligocene Mancora and Heath formations. Your new correspondent will bear these gaps in mind but is temporarily fully occupied with routine work. We wish Ben and his family good fortune in their new home, and look forward to seeing his careful systematic work embodied in future papers on Sumatran foraminifera.

The Lobitos Petroleum Company has hitherto used only the so-called “larger foraminifera”—species of Cyclammina, Bathysiphon, Robulus, etc., large enough to recognize with a hand lens - in subsurface zonation. Mr. A. J. Knights is starting on a more detailed approach, using the smaller species in zonation and applying paleo-ecologic principles. In due course these studies may establish the real reason for large-scale repetition in the subsurface section. In the literature this phenomenon has usually been attributed to slumping and low-angle gravity faults, but simple facies repetition is a possible alternative.

The Empresa Petrolera Fiscal is drilling some deep tests in the north and their micropaleontology will be handled by Sr. Eurribe.