BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 23, pp. 377-446 SEPTEMBER 12, 1912 



CRITEPJA FOR THE RECOGNITION OF ANCIENT DELTA 



DEPOSITS 



BY JOSEPH BAIIKELL ^ 



{Presented hefore Ui.e Society Deceiiiher 29, 1011) 



CONTENTS 



Page 



lutroduction 378 



Part I. — Larger relations of deltas 381 



Definitions of a delta and its parts 381 



Essential featnres of a delta 381 



The factors in delta constrnction and destiuctiou 383 



The bottoniset beds " 385 



The f oreset beds 385 



The topset beds . . . ^ 385 



Subaqueous plain 385 



The shore face and littoral zone 385 



Subaerial plain 386 



The Nile and Rhine deltas as examples 387 



Variations and blending in. the component parts of deltas 389 



Negative value of overlap 391 



Preliminary statement 391 



Transgress! ve overlap 392 



Overlap away from the source of supply 393 



The delta cycle and its use as a criterion of origin 395 



Comparison of the erosional and depositional theories 395 



Delta cycle with stationary crust 397 



Result of a movement of subsidence 399 



Imperfect application to present conditions 401 



Effects of recent crustal movements 401 



Resulting overemphasis of estuarine conditions 402 



Modern illustrations of ancient interior deltas 403 



The late Mesozoic delta cycle of the Atlantic Coastal plain 405 



Contrast of Mesozoic and l*aleozoic delta conditions in the Appalachian 



province 411 



Part II. — Evaluation of stratigraphic criteria 414 



Complexity of the problem 414 



Absence of fossils 415 



Color of sediments and the relative influence of location and climate 



thereon 41G 



1 Manuscript received by the Secretary of the Society January 10, 1912. 



XXVIII— Bull. Geol. Soc. Am., Vol. 23, 1911 (377) 



