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Studies of Florida, the Yucatan, and other nearby coastal areas have shown that (outside of tectonically disturbed belts), there are no Pleistocene reefs more than 10 m above present mean sea level. If interglacial times produced complete ice-cap melting, and a concomitant mean sea level rise, reef-building organisms should have flourished (a) farther north than now, and (b) higher above sea level than now. This distribution has not been found.
These studies also have shown that there are no obvious large pre-Sangamon coastal deposits away from major deltas. If the Sangamon and the Holocene were typical of Pleistocene interglacial times, then classical theory requires at least 2 more such deposits (Aftonian and Yarmouth). They either are not present or, if present, are not nearly as extensive as Sangamon accumulations.
Further studies of these areas have shown that there are no high flights of Pleistocene marine terraces. Those terraces within the study area commonly mapped as Pleistocene are very low features of Sangamon and Holocene age, or are higher features of Pliocene and Miocene age, or cannot be dated.
Several conclusions were made from these studies.
1. The cooling which brought on late Cenozoic ice ages must have occurred in the late Tertiary, rather than in the Quaternary.
2. Melting of the full set of ice caps, during Quaternary time, was never complete, including the present.
3. Sea level, in Quaternary time, never stood much higher than it is today.
4. Aftonian and Yarmouth sea levels were (a) slightly lower than in Sangamon and Holocene time, or (b) did not maintain a position, similar to now, long enough for significant deposits to be made, or (c) maintained such a position for so long that almost all deposits were removed by erosion.
5. The next long-term trend--barring short-term fluctuations--must be one of climatic cooling and a marked drop in mean sea level.
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