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Abstract: Paleozoic Depositional Previous HitSequencesNext Hit; Comparisons and Contrasts in Magnitude and Amplitude of Previous HitSeaNext Hit-Previous HitLevelNext Hit Changes

Charles A. Ross, June R. P. Ross

Using third-order depositional Previous HitsequencesNext Hit, Previous HitseaNext Hit-Previous HitlevelNext Hit fluctuations within Sloss' Paleozoic Sauk, Tippecanoe, Kaskaskia, and lower and middle parts of the Absaroka megasequences may be grouped into seven intervals of general Previous HitseaNext Hit-Previous HitlevelNext Hit highstands and lowstands. Similarity of depositional Previous HitsequencesNext Hit within each interval suggests that patterns in Previous HitseaNext Hit-Previous HitlevelNext Hit changes, and possibly the causes of these changes, remained fairly consistent through time intervals of 15 to 35 my.

Sauk third-order Previous HitsequencesNext Hit show a general rise of Previous HitseaNext Hit levels (15 my) which flooded the cratonic shelves. This was followed by a long interval (35 my) of high Previous HitseaNext Hit levels. The Sauk was terminated by an interval (15 my) of generally low Previous HitseaNext Hit levels (Whiterockian Stage).

The Tippecanoe is divisible into three intervals. The Mohawkian highstands (15 my) ended with a major lowstand. Succeeding Cincinnatian Previous HitcyclesNext Hit have greater amplitude (7 to 8 my). Latest Ordovician low Previous HitseaNext Hit levels lasted about 2 to 3 my. Early and Middle Silurian (25 my) flooding of cratonic shelves was gradual. After the Middle Silurian, Previous HitseaNext Hit Previous HitlevelNext Hit fell and remained relatively low during earliest Devonian (20 to 25 my).

Third-order Previous HitsequencesNext Hit in the Kaskaskia covered the cratonic shelves by the Middle Devonian and flooded most of the craton by the Frasnian (15 to 20 my). Famennian and early Tournaisian Previous HitcyclesNext Hit had relatively large fluctuations of Previous HitseaNext Hit levels. Visean Previous HitseaNext Hit levels remained relatively high and then fell abruptly near the end of the Mississippian. These low Previous HitseaNext Hit levels continued through the Early Pennsylvanian (20 my).

By the Middle Pennsylvanian (20 my), Absaroka depositional Previous HitsequencesNext Hit gradually transgressed onto the shelf. They were internally complex, relatively short (1 my), and with large amplitudes (100-200m). Low Previous HitseaTop levels near the end of the Pennsylvanian and the end of the Permian divide the Absaroka into lower (Pennsylvanian), middle (Permian), and upper (Triassic) parts.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994