STRUCTURE 639 



oils. It is probable, however, that the greater part of the latter are 

 derivatives of decay-resisting elements such as spore and pollen exines, 

 seed envelopes, and certain cuticles provided with resinous, waxy, or oily 

 protective substances mixed with other fat-, oil-, or albuminoid-producing 

 animal and plant ingredients high in hydrogen and low in oxygen found 

 in organic muds.^^ 



The following outline shows the principal stages in the origin and dis- 

 tribution of Appalachian oils, as the processes are understood by the 

 writer : 



Stages in Origin and Distribution of Appalachian Oils 



(Stages often overlapping) 



1. Deposition of organic muds and slimes, alternating with sands and some- 

 times calcareous beds. 



'2. Saturation (usually) with salt or salty waters (coming from overlying or 

 underlying beds where original accumulations were of fresh-water 

 origin). 



3. Burial (usually) by thick overlying sediments. 



4. Bio-chemical (bacterial) alteration and formation of oily substances. 



5. Occurrence of oil in minute particles widely disseminated. 



6. Migration of oil, largely upward, by capillarity, etcetera. 



7. Collection of oil in porous sands or other reservoirs. 



8. Gravitational separation of oil from water. 



9. Segregation of oil in small pools in slightly undulating and still unconsoli- 



dated deposits at moderate depths, assisted in cases by hydrostatic 

 movements, gas pressure, etcetera. 



10. Application (usually) of increasing load following continued deposition. 



11. Application of dynamic forces, with warping or folding. 



12. Cementation, with reduction of pore spaces. 



13. Migration of original oils, with collection in anticlines or below other ob- 



structions where water is present, or in synclines where water is absent. 



14. Formation of new oils by dynamo-chemical agencies. 



15. Dynamo-chemical alteration of certain of the original oils. 



16. Separation and rediffusion of some of the original oils, with the leaving 



behind of solid residues. 



17. Evolution of much new gas. 



18. General movement of oils and gas upward. 



19. Changes in composition of oils by filtration in upward passage. 



20. Changes in composition of oils by intermixture with one another. 



21. Changes in composition of oils by absorption of gas. 



22. General arrangement of oils according to stage of metamorphism as indi- 



cated by carbon ratio of coals (see page 649), with light oils nearest 

 zone of greatest dynamo-chemical activity and in deepest beds. 



^3 David White: "Some Relations in Origin between Coal and Petroleum." .Tour. 

 Wash. Acad. Sci., vol, 5, March 19, 1915, p. 192. 



