BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 28, pp. 553-602 September so, 1917 



REVISION OF THE STEUCTUEAL CLASSIFICATION OF 

 PETEOLEUM AND NATUEAL GAS FIELDS * 



BY FliEDEKICK C. CLAPP 



(Presented before the Society December 28, 1916) 



CONTENTS 



Page 



Introduction 554 



Review of the anticlinal theory 555 



Limitations of the anticlinal theory 556 



Statement of the structural theory 556 



History of the structural classification 557 



Popular misconceptions of the structural theory 559 



The structural classification 559 



Formulation of the classification 559 



Class I — Fields in aclinal or subaclinal structure 560 



Class II — Fields associated with anticlinal and synclinal structures . . 560 



General discussion 560 



Symmetrical anticlines 562 



Asymmetrical anticlines 562 



Subclass II [a) — Where strong anticlines exist standing alone. .. 562 

 Subclass II (6) — Where well defined alternating anticlines and 



synclines exist 565 



Subclass II (c) — Broad geanticlinal folds 565 



Subclass II ((?)— Overturned folds 567 



Subclass II (e) — Lenticular nature of the sands 567 



Class III — Monoclinal structure 568 



General discussion 568 



Cause of monoclinal accumulations 569 



Types of interruption 571 



Subclass III {a) — Monoclinal noses 572 



Subclass III ( & ) — Monoclinal ravines 572 



Subclass III (c) — Structural terraces or "arrested anticlines"... 572 

 Subclass III {d) — Accumulations on monoclines due to thinning 



out or change in texture of the sand 573 



Class IV — Quaquaversal structures, or "domes" 574 



General discussion • 574 



Subclass IV {a) — Anticlinal bulges or "cross-anticlines". 574 



* Manuscript received by the Secretary of the Society February 26, 1917. 



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