--> Abstract: Response Of Cenomanian-Turonian (Late Cretaceous) Foraminifera To High Frequency Changes In Relative Sea Level In The U.S. Western Interior Sea, by R. M. Leckie, O. Snoeyenbos-West, and E. L. Leithold; #90928 (1999).
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LECKIE, R. MARK1, OONA SNOEYENBOS-WEST1, and ELANA L. LEITHOLD2
1Univ. of Massachusetts, Amherst, MA
2North Carolina State Univ., Raleigh, NC

Abstract: Response of Cenomanian-Turonian (Late Cretaceous) Foraminifera to High Frequency Changes in Relative Previous HitSeaNext Hit Previous HitLevelNext Hit in the U.S. Western Interior Previous HitSeaNext Hit

During episodes of transgression and highstands of Previous HitseaNext Hit Previous HitlevelNext Hit, subtropical water masses invaded the U.S. Western Interior Previous HitSeaNext Hit (WIS) from Tethys. One such episode occurred during the late Cenomanian-middle Turonian third-Previous HitorderNext Hit "Greenhorn Previous HitCycleNext Hit".

Assemblage analysis shows that benthic taxon dominance correlates to the third-Previous HitorderNext Hit transgression and regression of the WIS and fourth-Previous HitorderNext Hit Previous HitseaNext Hit Previous HitlevelNext Hit fluctuations. Six fourth-Previous HitorderNext Hit cycles are recognized from AZ to MT. Subtropical water masses rapidly moved into the seaway with transgression. Benthic conditions abruptly improved and normal marine, warm water molluscs, foraminifera, and calcareous nannoplankton invaded the seaway. This event also coincides with the onset of a global perturbation in the carbon system (Oceanic Anoxic Event 2).

Neobulimina, an infaunal taxon, dominated during the late third-Previous HitorderNext Hit transgression and highstand when warm, oxygen-poor Tethyan waters advanced into the seaway. In contrast, the epifaunal/shallow infaunal taxon Gavelinella proliferated briefly during times of water mass mixing (coupled with increased influx of terrigenous and/or marine organic matter?) at/near fourth-Previous HitorderNext Hit low stands. Neobulimina returned during fourth-Previous HitorderNext Hit transgressive pulses with renewed expansion of oxygen-poor Tethyan water masses. Neobulimina and the biserial planktic foram Heterohefix show a significant correlation with carbonate content suggestive of fifthorder parasequences.

During third-Previous HitorderNext Hit regression, Tethyan waters were replaced by cooler, lower salinity water masses of Boreal affinity as marked by an abrupt change to agglutinated benthic foraminifera and loss of nearly all planktic foraminifera. The WIS foraminifera responded to fluctuating Previous HitseaNext Hit Previous HitlevelTop and its influence on water mass distribution, organic matter flux, and benthic oxygenation.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas