Interpenetrating Irregular Spherulitic Radial Ooids - Carboniferous (O/23/Carb/Aust)
10x
|
10x
|
2.5x
|
5x
|
5x
|
10x wave plate
|
2.5 cross nicols
|
5x cross nicol
|
5x cross nicol
|
10x wave plate
|
10x wave plate
|
2.5 wave plate
|
5x wave plate
|
5x wave plate
|
Outstanding feature |
Spherulitic radial calcite ooids, quartz, volcanic rock fragments(?), & equant spar |
Folk Classification |
Oosparite |
Dunham Classification |
Oolitic Grainstone |
Common Grains |
Ooids,quartz& volcanic particles |
Sorting |
Good |
Rounding |
Good |
Micritization & envelopes |
Most grains have thin micrite envelopes |
Cement & diagenetic fabric |
Equant spar |
Porosity |
Dense |
Depositional Setting |
Highly saline high energy shoal water |
Diagenetic history |
Cementation by freshwater calcite followed by interpenetration of grains |
The sparse equant spar cements are probably freshwater cements dissolved from original aragonite and calcite. The radial calcite ooids accumulated on high energy shoals. Note ooid nucleae of quartz and volcanic material. Darkened grain rims are infestation of cyanobacteria colonies that cause local micritization. The sperulitic character of the ooids is interpreted to suggest that they formed and accumulated in a more restricted, probably highly saline, setting. However the skeletal grains are probably transported into this more restriced setting. The interpenetration of the ooids is interpreted to suggest that this section has potentially seen burial at sufficient depth to cause this effect; maybe the sediment was buried to 10,000 ft or more???
Thursday, November 11, 2021