scriptions; (3) their importance for correlation and paleoecological interpreta- 

 tions; and (4) their use in selecting and recommending favorable areas for petro- 

 leum exploration. The length of discussion of each group of microfossils will be 

 relative to its considered future importance. Emphasis is placed on some of the 

 microfossils, such as spores, pollen, hystrichospherids and microforaminifera 

 that have been introduced only recently by oil companies into their paleontolog- 

 ical laboratories. 



One of the most important responsibilities confronting the oil company 

 paleontologist is the rapid identification of the fossils encountered in routine 

 examination of well samples. He must not only be able to recognize the fossils 

 observed under the microscope, but know their geologic ranges and particular 

 environment under which they were deposited. In a wildcat area this informa- 

 tion must be relayed quickly to the well-site geologist so as to keep him informed 

 of the age and, if possible, the depositional environment of the sediments being 

 penetrated. Although the majority of proved field wells are correlated litholog 

 ically by the well-site geologist, information supplied to him by the micropaleon- 

 tologist can aid him in correlating wells drilled on salt domes and other struc- 

 turally complex areas. Unless he knows the age of the penetrated sediments, use- 

 less, expensive drilling might be continued in strata known to lack favorable res- 

 ervoir rocks. 



Until recently, paleontologists relied primarily on foraminifera for age 

 determinations and zonal correlation. In many instances foraminifera are scarce 

 and poorly preserved, and they are not indicative of age nor of value as zone 

 markers. Where the strata are barren of foraminifera, the stratigrapher must 

 rely primarily on lithology and electric logs for establishing correlations. 



Plant spores, pollen, hystrichospherids, or other types of microfossils are 

 found in approximately 90 percent of all sediments. Because of this wide dis- 

 persal, the economic paleontologist has an excellent opportunity (1) to make 

 rapid age determinations, (2) to correlate the strata, and (3) to evaluate forma- 

 tions for oil possibilities. 



Wilson (1956) pointed out that a paleontologic study that utilizes all the 

 organisms present to determine paleoecological conditions should be of propor- 

 tionally greater value to stratigraphy than one devoted to a single group of fos- 

 sil animals or plants. The economic paleontologist of today should be well ac- 

 quainted with various types of microfossils so that more critical evaluation of 

 composite assemblages can be made. Many oil-company paleontologists have 

 disregarded all microfossils except the foraminifera, and thus have by-passed 

 much useful information. 



Zoning 



It is desirable in many instances to zone a formation so that more accurate 

 correlations can be made. Microfossil zones are established by three methods: 



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