INTRODUCTION 555 



The structural factor has been realized for several decades by the ex- 

 ponents of the anticlinal theory, and in 1910^ the structural classification 

 was proposed as an offshoot of that theory. The purpose of this paper is 

 to broaden the subject by discussing, first, the classification, and secondly 

 the apparent exceptions. We might almost say that the knowledge of 

 favorable structures is approaching a stage where the exceptions will 

 be more important than the rule; but, nevertheless, the structural rules 

 themselves remain the predominant guide in any field investigation. 



In revising the classification, it is a pleasure to give credit for a num- 

 ber of additions to Bosw^orth," Johnson and Huntley,^ Mrazek,* and others. 

 The writer also is indebted to the McGraw-Hill Book Company, to the 

 United States Geological Survey, and to Economic Geology for permis- 

 sion to make copies of certain cuts republished here. 



Eeview of the anticlinal Theory 



In considerations of geological structure much has been heard in the 

 past about the "anticlinal theory," whi(^h has been of decided value in 

 locating many oil and gas fields. That theory was first suggested by 

 Hunt^ and was later investigated and advocated by Andrews,^ WinchellJ 

 Stevenson,^ Minshall,^ Newberry,^*^ Hofer,^^ and others. The theory was 

 not definitely formulated, however, until 1885, when Doctor Whiter- 

 worked out its details and first applied the theory in practice by locating 

 oil and gas fields in West Virginia and Pennsylvania by means of it. 



^A proposed classification of petroleum and natural gas fields based on structure. 

 Read before the Geological Society of Washington March 9, 1910. Abstract, Science, 

 vol. 31, no. 801, May 6, 1910. pp. 718-719. Published in full in Econ. Geol., vol. 5, no. 

 0. Sept., 1910, pp. 503-521. 



The use of geological science in the petroleum and natural gas business. Proc. 

 Engrs. Soc. W. Pa., vol. 26, no. 4, May, 1910, pp. 87-120. Read before that Society 

 April 19, 1910. 



2 T. O. Bosworth : Outlines of oil-field geology. Pet. Review, March-April, 1912, pp. 

 139-140, 171-172. 203-204, 235-236. 



3 Principles of oil and gas production, 1916, pp. 63-66. 



* R. L. Mrazek : Congress International du Petrole, 1907. 



^ T. Sterry Hunt : Notes on the history of petroleum or rock oil. Can. Nat., vol. 6, 

 August, 1861, pp. 241-255 ; Can. Geol. Survey, 17th Rept. of Progress, 1863-1866, p. 233. 



® E. Benjamin Andrews : Rock oil, its geologic relations and distribution. Am. Jour. 

 Sci., 2d ser., vol. 32. 1861, pp. 85-93. 



^ Alexander Winchcll : On the oil formation in Michigan and elsewhere. Am. Jour. 

 Sci.. 2d ser„ vol. 39, 1865, p. 352. 



* J. J. Stevenson : Sec. Geol, Survey of Pa., vol. H, 1875, pp. 394-395. 



« F. W. Minshall : In letters to the State Journal, Parkersburg, W. Va., in 1881. 



10 J. S. Newberry: Geol. Survey Ohio, vol. 1, 1873, p. 160. 



" Hans Hofer : Das Erdol und seine Verwandten, 3d edition, p. 166 ; Geologie des 

 Erdols, p. 18. 



" I. C. White : Sci., vol. 6, June 26, 1885 ; Bull. Geol. Soc. Am., vol. 3, 1892, pp. 187- 

 216; W. Va. Geol. Survey, vol. 1-A, 1904. pp. 48-64. 



XLIII — Bull. Geol. Soc. Am.. Vol. 28, 1916 



