Abstract

A paraconformity separates vadose-cemented eolianites from modern uncemented dune sands on Isla Cancun. Structures and textures which could be preserved in the rock record to indicate this paraconformity include: 1) stairstep erosional surfaces where weakly cemented older eolianite has been differentially eroded along bedding planes, 2) sand-filled polygonal cracks apparently formed by compaction, 3) local encrustation of the older eolianite's surface by algae and/or incipient calichification, 4) small solution pits, 5) wind-scour marks, and 6) a variety of pseudoburrow structures formed by vegetation, ants, and dissolution. Comparable paraconformities are probably common in the rock record but would be difficult to recognize because 1) rocks above and below are of similar composition, 2) large exposures are needed to recognize the diagnostic structure, 3) pseudoburrows may be abundant, and 4) distinctive diagenetic textures may be obscured by subsequent diagenesis. Furthermore, eolianites such as these have low preservation potential. However, the diagnostic textures for recognizing this paraconformity could form in subtidal carbonates during subaerial exposure, or along a subtidal paraconformity surface by submarine erosion of semilithified marine-cemented bottom sediments.--Modified journal abstract.

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