composite samples from at least three boreholes triangularly arranged. By count- 

 ing the plant spores in the Morrow and Atoka formations from numerous wells 

 in the Seminole area of Oklahoma, it was found that the isobotanical lines show- 

 ing the greatest abundance of spores were parallel and nearest to oil fields. In 

 areas which consistently had dry holes, the sediments contained very few spores. 

 In a broad sense, an abundance of plant spores and pollen could indicate a 

 favorable area for oil exploration where the reservoir rock is sandstone; an 

 abundance of hystrichospherids might indicate a favorable area for petroleum 

 possibilities where the reservoir is a reefal limestone; and the abundance of mi- 

 croforaminifera could indicate an unfavorable area for oil accumulation because 

 reservoir rocks might be lacking. 



Preparation Techniques 



The remains of microfossils are either calcareous, siliceous, chitinous, pro- 

 teinaceous, cellulose, phosphatic, or carbonaceous. To obtain the different types 

 of microfossils from a particular sample, it is necessary to divide the material 

 so that separate preparation methods can be used for each portion of the sample, 

 depending on the chemical composition of the microfossils, their size, and the 

 character of the sediment. Because of differences in composition of microfossils 

 and their entombing sediments, preparation procedures will vary not only with 

 a particular sample but also with different types of lithology. Space does not 

 permit an account of the various preparation techniques. The reader should, 

 therefore, refer to the published details of these methods, which are generally in- 

 cluded in papers dealing with particular groups of microfossils. However, some 

 general preparation techniques are briefly described below. 



For Acid-Soluble Microfossils 



The sample, if not indurated, is broken into ± 1/4-inch fragments and 

 soaked in water (boiled if necessary) for several hours. It then is washed 

 through a nest of sieves (80, 100, 150 mesh) to remove the fine elastics. In some 

 instances, it is feasible to concentrate the microfossil assemblage by heavy liquids 

 such as bromoform or carbon tetrachloride. If the sample is well indurated, it 

 may be necessary to prepare thin sections for studying the microfossil content. 



For Acid-Insoluble Microfossils 



The shale sample is broken into fragments ± 1/4-inch. It is then placed in 

 a copper beaker, covered with 52 percent hydrofluoric acid, and allowed to re- 

 main under a hood for 16 hours; or the sample can be boiled in the acid for 5 

 minutes if rapid examination is desired. The residue is then diluted with dis- 

 tilled water and is centrifuged repeatedly until all acid is removed. A few drops 

 of a 1 percent solution of Safranine Y stain is then added. The sample is then 



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