Skeletal - Calcareous Algae - Cyanobacteria (Al/5/Jur/Eng)
 2.5x
|
 2.5x cross nicols
|
 2.5x wave plate
|
 5x
|
 5x wave plate
|
 2.5x
|
| Outstanding feature |
Algal laminae with pseudomorphs of gypsum filled by calcite spar |
| Folk Classification |
Micrite layer interbedded with pelsparite. The spar pseudomorphs gypsum blades |
| Dunham Classification |
Mudstone layer interbedded with pellet packstone. Calcite cement pseudomorphs gypsum blades |
| Common Grains |
Pellets and calcite blades pseudomorph gypsum |
| Sorting |
Poor |
| Rounding |
Poor |
| Micritization & envelopes |
Micritic intraclasts and pellets |
| Cement & diagenetic fabric |
Calcite blades pseudomorph gypsum rossettes |
| Porosity |
None |
| Depositional Setting |
Upper tidal flat to upratidal tidal flat with algal mats overlieing a gypsum mush |
| Diagenetic history |
Replacement of gypsum by calcite |
Fossil Forest, Jurassic age sediments from Lullworth Cove, Dorset in the U.K. Fabric replacement by micrite and spar; gypsum blades replaced by calcite spar. This thin section that cuts across both the fabric of algal stromatolites and their associated diagenetic fabric from an intertidal to supratidal setting.
Thursday, November 11, 2021