History of stage 5 sea level in Bermuda: Review with new evidence of a brief rise to present sea level during Substage 5a

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sea level change


Oxygen-isotope Substage 5e is represented by the Devonshire Formation in Bermuda. The occurrence of these coastal-marine deposits to about 5 m indicates Pleistocene sea-level data in Bermuda do not need tectonic corrections.

A few published U-series coral dates suggest that a conglomerate (Spencer's Point Formation) may have formed during Substage 5c. Geologic mapping, however, indicates that the eolianite beneath the conglomerate is pre- rather than post-Devonshire Formation in age as was previously thought, and the aminostratigraphy of marine sheels also confirms the correlation of the Spencer's Point and Devonshire Formations.

Substages 5c and 5a are represented by the Southampton Formation. Large eolianites comprise the bulk of this formation. They are onlapped by a few, small, younger marine (+1 m) and eolian deposits. Aminostratigraphy confirms that these late Southampton age deposits are significantly younger than the Devonshire Formation, and U-series dates indicate a Substage 5a age. The setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms. This evidence that sea level in Bermuda was at about present datum late in Substage 5a agrees with interpretations of Neotyrrhenian deposits of Mediterranean shorelines, but not with inferences from the deep-sea oxygen-isotope record, or with data from uplifted coral reefs.