Ooids Washed into Low Energy Micrites Cretaceous (O/39/Cret/Tex)
2.5x
|
5x
|
5x
|
5x
|
5x
|
2.5 cross nicols
|
2.5 wave plate
|
5x wave plate
|
Outstanding feature |
High Energy Ooids & Bioclasts - Micrite Matrix |
Folk Classification |
Fossiliferous Oomicrite |
Dunham Classification |
Fossiliferous Oolitic Packstone |
Common Grains |
Ooids, Molluscan Fragments, Echinoids & Quartz |
Sorting |
|
Rounding |
|
Micritization & envelopes |
Common to pelecypod tests |
Cement & diagenetic fabric |
Common to pelecypod tests |
Porosity |
None |
Depositional Setting |
Low energy shoal to lea of high energy shoal |
Diagenetic history |
Micritization of fossil particles and ooids |
Striking mix of high energy grains within micrite matrix suggests juxtoposition of the low and high energy settings. Radial calcitic ooid cortex is concentricly layered about nucleae of both micritic pelloids and fossils. Other transported grains include grapestones and broken fossil tests (oysters, thin shelled pelecypods, & gastropods). Darkened spots within ooid layers and micrite envelopes are cyanobacteria colonies that caused local micritization when high energy grains came to rest in this setting. Common stylolites show disolution at their boundaries and concentration of the insoluble angular quartz silt common dispersed through the sample.
Thursday, November 11, 2021