CHAPTER 4 



SUBSURFACE LABORATORY METHODS 



MICROPALEONTOLOGIC ANALYSIS 



L. W. LeROY 



Prior to 1925, micropaleontology played an insignificant role in 

 stratigraphic and paleontologic investigations. It was not until that year 

 that the science was recognized and appreciated as a valuable tool in 

 surface and subsurface problems of the petroleum industry. All major 

 and many minor oil companies now sponsor micropaleontologic labora- 

 tories. 



The economic micropaleontologist is essentially a microstratigrapher. 

 His time is not only devoted to the paleontologic aspects of strata, but 

 also to lithology, to detrital mineralogy, and to the many other techniques 

 which aid in the solution of stratigraphic problems. 



Methods followed by micropaleontologists are extremely variable 

 and are controlled by the type of problem (surface or subsurface), the 

 time allocated to the problem, the quality of personnel involved, and 

 company policy. In some areas only major faunal divisions of sections 

 are desired, whereas in other areas it is necessary to introduce detailed in- 

 vestigations before the problem under consideration can be properly 

 solved. The micropaleontologist should be familiar with the field geolo- 

 gist's assignment and should visit field operations whenever it is deemed 

 necessary in order to coordinate the laboratory work properly. He should 

 systematize laboratory routine so that data may be obtained as soon as 

 possible for final analysis. It should be remembered that most micro- 

 paleontological problems are of the "pressure" variety, and that not un- 

 commonly management desires results before the project is started. The 

 micropaleontologist must be versatile, having a knowledge of all varieties 

 of microfaunas as well as being able to evaluate their significance and rec- 

 ognize their use limitations. 



Micropaleontology has aided materially in evaluating unconformi- 

 ties, structural conditions, and facies changes, in dating and correlating 

 strata, and in interpreting depositional environments. The science has its 

 limitations, and this fact should be recognized; otherwise, incompetent con- 

 clusions and interpretations may be introduced. Micropaleontologic data 

 should be coordinated with all other available stratigraphic information. 



Only those microfossils that have been used by paleontologists in 

 the oil industry are discussed here briefly. Some types are more applic- 

 able in the solution of stratigraphic problems than are others. Those 

 herein considered are Foraminifera, ostracodes, Radiolaria, conodonts, 

 otoliths, fish scales, calcareous algae, diatoms, spores and pollen, and 

 grass seeds. 



