Radial Calcitic Ooids - Crinoid Ossicles Common - Mississippian (O/19/Miss/Ky)
2.5x
|
5x
|
5x
|
5x
|
2.5 cross nicols
|
5x cross nicol
|
2.5 wave plate
|
5x wave plate
|
5x wave plate
|
5x wave plate
|
Outstanding feature |
Radial calcitic ooids, crinoid ossicles and circumgranular cements and equant spar |
Folk Classification |
Oosparite |
Dunham Classification |
Oolitic Grainstone |
Common Grains |
Ooids, & crinoid ossicles |
Sorting |
Good |
Rounding |
Good |
Micritization & envelopes |
Most grains |
Cement & diagenetic fabric |
Bladed calcite rims and equant spar |
Porosity |
Dense |
Depositional Setting |
Open marine high energy shoal water |
Diagenetic history |
Cemented by vadose freshwater calcite leached from the original aragonite grains |
The isopachus rim cements are related to inital freshwater cements dissolved from original aragonite and calcite. The radial calcite ooids accumulated adjacent to the tidal channel seen in outcrop on Rt 64 close to Carter Caves in Kentucky. Note ooid nulceae of crinoid ossicles and echinoid spines. There appear to be a few botryoidal grains enclosed by radial ooid coating. Darkened spots within bioclastic layers are cyanobacteria colonies that cause local micritization. Some grains may have been bored by sponges.
Thursday, November 11, 2021