Abstract Quaternary carbonate eolianites on Babaroian islands form a complex constructional topography composed of deposits formed during different glacioeustatic sea-level highstands. These eolianites constitute spatially and temporally discontinuous sediment packages. Within deposits formed during individual sea-level highstand events, eolianites from transgressive, stillstand, and regressive phases can be differentiated, but only if exposure is good and detailed study is undertaken. The eolianites may be stacked atop one another, or they may be in contact with marine deposits. Eolianites may overlie older marine deposits, interfinger with coeval marine rocks, or be overlain by younger marine facies. Depositional packages including eolianites that are deposited during a single sea-level highstand are commonly bounded above and below by erosion surfaces characterized by terra rossa paleosols. However, the patchiness of eolian deposition, the occurrence of calcarenite protosols, possible erosion of a paleosol during an ensuing transgression, and the possibility of soil movement downward into karst features can create confusion about actual unit boundaries. Interpretation of carbonate eolianite sequences in the ancient rock record may be enhanced if the complexities of the Quaternary eolianite record are appreciated. The depth of study required to successfully interpret well-exposed Quaternary eolianites implies that ancient eolianites, with less exposure and greater diagenesis, are unlikely to be resolved to a similar degree.

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Abstract Karst development on carbonate platforms occurs continuously on emergent portions of the platform. Surficial karst processes produce an irregular pitted and etched surface, or epikarst. The karst surface becomes mantled with soil, which may eventually result in the production of a resistant micritic paleosol. The epikarst transmits surface water into vadose pit caves, which in turn deliver water to a diffuse-flow aquifer. These pit caves form within a 100,000 yr time frame. On islands with a relatively thin carbonate cover over insoluble rock, vadose flow perched at the contact of carbonate rock with insoluble rock results in the lateral growth of vadose voids along the contact, creating large collapse chambers that may later stope to the surface. 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 collapse of caves, which produces upwardly prograding voids whose current position does not correlate with past sea level positions. The location and type of porosity developed on emergent carbonate platforms depend on the degree of platform exposure, climate, carbonate lithology, and rate of sea level change. Slow, steady, partial transgression or regression will result in migration of the site of phreatic void production as the freshwater lens changes elevation and moves laterally in response to sea level change. The result can be a continuum of voids that may later lead to development of solution-collapse breccias over an extended area.