Aragonite Ooids - Meniscus Cements - Botryoidal Grapestones - Holocene (O/8/Hol/Bah)
10x
|
10x
|
10x
|
2.5x
|
2.5x
|
20x
|
20x
|
5x
|
5x
|
5x
|
5x
|
5x cross nicol
|
5x wave plate
|
5x wave plate
|
Outstanding feature |
Meniscus cements & concentric aragonite ooids |
Folk Classification |
Oosparite |
Dunham Classification |
Oolitic grainstone |
Common Grains |
Ooids, & botryoidal grapestones |
Sorting |
Good |
Rounding |
Good |
Micritization & envelopes |
Limited to a few grains |
Cement & diagenetic fabric |
Meniscus low magnesian calcite rims |
Porosity |
5-7% Interparticle porosity |
Depositional Setting |
Open marine high energy shoal water |
Diagenetic history |
Cemented by vadose freshwater calcite leached from the original aragonite grains |
The striking meniscus cements are related to evaporation of freshwater charged with dissolved aragonite within the beach rock forming adjacent to the tidal channel that marks the southern margin of the Joulters Cay. Aragonite ooids with concentric layering of cortex about micritic pelloid nulceae. Botryoidal grains are transported grapestones that form nucleae and are enclosed by aragonite ooid coating. Darkened spots within ooid layers are cyanobacteria colonies that cause local micritization.
Thursday, November 11, 2021