About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 50 (1966)

Issue: 3. (March)

First Page: 640

Last Page: 640

Title: Systematic Interpretation of Previous HitUnconformitiesNext Hit: ABSTRACT

Author(s): Harry E. Wheeler

Article Type: Meeting abstract


The term unconformity is applied to first-order discontinuities which bound major continental framework sequences. Regional and interregional identity and continuity of most Previous HitunconformitiesNext Hit have remained unappreciated because: (1) they normally are erased in many areas by later degradation; (2) empirical criteria are inconsistently developed and commonly obscure the Previous HitunconformitiesNext Hit; (3) most empirical criteria do not make it possible to distinguish between Previous HitunconformitiesNext Hit and countless small-magnitude discontinuities; (4) conventional stratigraphy is depositionally, but not degradationally, oriented; (5) unconformably separated sequences commonly are erroneously equated and thus mistakenly interpreted as facies; (6) miscomprehension of the base-level concept has resulted in ailure to relate episodically contemporaneous marine, non-marine, and volcanic successions; (7) individual Previous HitunconformitiesNext Hit are too commonly conceived to be of a single type rather than to represent several or all types; (8) diagnostic faunas commonly are absent from critical strata; and (9) many biostratigraphic standards are inadequate to define Previous HitunconformitiesNext Hit.

Failure to recognize these obstacles has led in many cases to the fallacious expedient of interpreting events directly from the unconformity-riddled and thus degradationally fragmented stratal record. As a result, the occurrence of alternating interregional depositional and degradational episodes generally has remained unappreciated, and many conventional interpretations are erroneous.

Because all Previous HitunconformitiesNext Hit have certain phenomena in common, particularly in regard to their manner of development, and because the beds above and below an unconformity repeatedly have certain relations to one another and to the unconformity separating them, certain axioms and corollaries can be stated that apply specifically to Previous HitunconformitiesNext Hit. It is believed that analytical procedures devised and carried out in the light of these axioms and corollaries provide a systematic basis for the interpretation of Previous HitunconformitiesTop and for their distinction from the myriads of minor breaks.

End_of_Article - Last_Page 640------------

Copyright 1997 American Association of Petroleum Geologists