Ooid Aragonite Cortex Dissolved - Matrix of Calcite Spar - Pleistocene (O/17/Ple/Fla)

2.5 cross nicols
5x cross nicol
2.5 wave plate
5x wave plate
Outstanding feature Dissolution of aragonite ooid cortex
Folk Classification Porous oosparite
Dunham Classification Porous oograinstone
Common Grains Dissolving ooids
Sorting Well sorted
Rounding Well rounded
Micritization & envelopes Ooids, some micritized & most dissolving
Cement & diagenetic fabric Well cemented by freshwater calcite
Porosity 20% intragranular porosity
Depositional Setting High energy shoal
Diagenetic history Dissolution or aragonite and precipitation of freshwater calcite spar

Striking Pleistocene high energy concentric aragonite ooid grains that accumulated on tidal deltas formed in the vicinity of Le Jeune, Miami Florida. Note the empty pores within the ooids that are the product of dissolution of aragonite cortex by freshwater. The remanents of mucilagenous material secreted by cyanobacteria now form the dark layers in the dissolved ooids and should act as the template for later cement fill if that should eventually fill these voids. The earlier carbonate that has is dissolved is currently reprecipitated as a low magnesium calcite spar matrex.

Thursday, November 11, 2021
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