Microscopic

Beach/Dune Rock - Aragonite Ooids - Meniscus Cement- Holocene (O/7/Hol/Bah)

10x
10x
10x
2.5x
5x
2.5 cross nicols
Outstanding feature High energy concentric aragonite ooids
Folk Classification Porous well sorted ooidsparite
Dunham Classification Porous well sorted ooid grainstone
Common Grains Ooids
Sorting Well sorted
Rounding Well rounded
Micritization & envelopes A few coated grains
Cement & diagenetic fabric Meniscus cements at grain contact; some dissolution by boring cyanobacteria
Porosity 45% intergranular porosity
Depositional Setting Aeolian dunes by high energy ooid shoal
Diagenetic history Precipitation of freshwater meniscus calcite, probably derived from dissolution of the original aragonite ooids

Striking high energy concentric aragonite ooid grains formed into aeolian dunes ridges that cap parallel trending intertidal spits that collected adjacent to the high energy ebb deltas in the vicinity of Joulters Cays on the NE margin of the Great Bahamas Bank. Note the meniscus cements formed at the points of contact of the ooid grains. Also note the empty pores within some of the ooids that are the product of dissolution induced by boring cyanobacteria (blue-green algae).


Monday, August 27, 2018
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