Publication: Root calcret formation on Quaternary karstic surfaces of Grand Cayman.
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2007
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Instituto de Ciencias de la Tierra "Jaume Almera" (Barcelona)
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Abstract
The rugged karst terrain developed on the dolostones of the Miocene Cayman Formation (Fm) on Grand Cayman
includes numerous large cavities that formed through the activity of tree roots. The surfaces of those cavities
are coated with laminated calcrete crusts up to 8 cm thick that are formed of an alteration zone, an accretionary
zone, and final infill of the cavities. These crusts are formed of various laminae, including dolostone
with root traces, alveolar septal structures, peloids, micritic and microsparitic laminae, micrite with bioclasts,
and pisoliths. Features such as microborings, spores, needle-fiber calcite and micro-rods are common in all
parts of the calcrete crust. Calcrete formation was initiated as the roots and associated microorganisms generated
the cavities. Later on trapping and binding processes and organically induced precipitation of carbonate
allowed the formation of the accretionary (mostly laminar) part of the calcrete. The last phases of crust formation
took place when ponded waters filled the cavities. The calcrete crusts developed on the Cayman Formation
dolostones record a very specific setting for calcrete formation and constitute a good example of non-horizontal
calcrete crusts.