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The AAPG/Datapages Combined Publications Database
AAPG Special Volumes
Abstract
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* John E. Mylroie
* ABSTRACT Carbonate islands record successive sequences of paleosols (platform emergence) and carbonate sedimentation (platform submergence). The appropriate interpretation of paleosols as past exposure surfaces is difficult, because carbonate deposition is not distributed uniformly, paleosol material is commonly transported into vadose and phreatic voids at depth, and micritized zones similar in appearance to paleosols can develop within existing carbonates. On carbonate islands, large dissolution voids called flank margin caves form preferentially in the discharging margin of the freshwater lens from the effects that result from freshwater/saltwater mixing. Similarly, smaller dissolution voids also develop at the top of the lens where vadose and phreatic freshwaters mix. Independent of fluid mixing, oxidation of organic carbon and oxidation/reduction reactions involving sulfur can produce acids that play an important role in phreatic dissolution. This enhanced dissolution can produce caves in freshwater lenses of very small size in less than 15,000 yr. Because dissolution voids develop at discrete horizons, they provide evidence of past sea level positions. The glacio-eustatic sea level changes of the Quaternary have overprinted the dissolutional record of many carbonate islands with multiple episodes of vadose, freshwater phreatic, mixing zone, and marine phreatic conditions. This record is further complicated by
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