ABSTRACT: Maps of North America Showing the Units Directly Below and Above the Six Major Unconformities
Donald Eugene Owen
The exploration of North America for hydrocarbon and ore deposits has provided a vast amount of surface and subsurface information on the Phanerozoic depositional and tectonic history of the continent and has made possible the detailed mapping of the major interruptions of the depositional sequences (the major unconformities) and of the associated changes in tectonic patterns.
Twelve maps of North America (scale of 1:5,000,000) have been prepared that show the units which lie directly above and below those unconformities which represent the six interruptions of greatest temporal and areal extent. Five of these coincide with the sequence boundaries identified by L. L. Sloss; the sixth lies within the Kaskaskia Sequence.
The temporal extent of each of these major interruptions varies greatly from place to place. In some local areas, deposition may have continued without any significant interruption while elsewhere the time it took to bury the older eroded rocks was several tens of millions of years.
Many tectonic features remained more or less permanent throughout a large part of Phanerozoic time; other areas show quite complex tectonic histories. The mapping of the changes in tectonic patterns that occurred in North America should assist in putting together a clearer picture of the tectonics of the planet.
The six sets of paired maps also outline areas where the proper units lie below and above each unconformity to provide reservoir and source beds for hydrocarbon accumulations.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990