We have discussed sea level yoyo's from the Pleistocene ice age of which it is suggested that it balances with the ice volume paced on the poles. So all of a sudden a study pops up (courtesy of the author), Dr Madeleine Briskin:
So you have cyclic sea level changes but supposedly no ice sheet to exchange the water volume with. The conclusion, barring an ice sheet yoyo, to tie the sea level changes to changes in the Earth's geometry caused by the Milankovitch eccentricity cycle is not supported by a mechanism. Anybody?abstract
Sea level movements with quasi-periodicity of 430,000 years are identified in the marine sedimentary units of the Eastern Gulf Coastal Plain of Mississippi, Alabama and Georgia which represent a 5.8 million year record of strandline displacement during Paleocene time. Principal component analysis of the benthic foraminiferal fauna yielded six assemblages which when combined with two other qualitatively derived assemblages provided paleoecologic information which clearly reflects the influence of paleocirculation and paleoclimatic regime of the Eastern Gulf Coastal Plain.
The presence of the planktonic foraminiferal taxa Subbotina trinidadensis and Planorotalites pseudomenardii as well as paleolatitudes ranging from 15degrees N (for the Campeche Shelf) to 25degreesN (for the Coastal Plain) emphasizes a paleoclimatic regime which is dominantly tropical. A paleoceanographic model was derived which suggests that normal marine waters were brought into the Gulf of Mexico by two major currents:
1) the easterly flowing Pacific countercurrent which when deflected by the southernmost Gulf margin generated a minor cyclonic flow around the Campeche Shelf and
2) the west flowing equatorial Atlantic current generated by the southern margin of the North Atlantic anticyclonic gyre which fed the Central and Northern Gulf.
When integrated into the paleoceanographic model, the distribution of continental shelf benthic foraminiferal assemblages indicates a pattern which is dominantly controlled by:
1) the character of the circulation,
2) water mass properties,
3) latitudes and climate,
4) distance from the strandline.
Strandline displacements are related to transgressive and regressive sea level movements in an ice free Paleocene world. The well delineated 430,000 year quasi-periodic cycle observed in the sea level curve is identified as being astronomical in character. These results support the view that changes in the earth's orbit may trigger changes in the geometry of the Earth's surface in a way which causes sea level to oscillate with a quasi-periodicity of 430,000 years.
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