Microscopic

Fecal Pellets in Spar Cement - Jurassic (Pel/10/Jur/Eng)

10x
10x
2.5x
2.5x
5x
5x
5x cross nicol
Outstanding feature Elongated Fecal Pellets in a Matrix of Calcite Cement. Few Fossils.
Folk Classification PelSparite
Dunham Classification Pelgrainstone
Common Grains Fecal Pellets with sparse pelecypod valves
Sorting  Well sorted
Rounding  Well rounded
Micritization & envelopes Slight alteration of margins of bioclasts
Cement & diagenetic fabric Calcite
Porosity  
Depositional Setting Low energy
Diagenetic history Pellets hardened at excretion and cemented during burial.

This is a typical fecal pellet carbonate that accumulated in a low energy probably restricted setting, since there seem to be few bioclasts. Note the lack of interpenetration supporting the interpretation that these grains hardened shortly after they were excreted. The setting of these sediments appears to have ranged from marine, to evaporitic to fresh water on the basis of the sedimentary association with the Purbeck Formation and Fossil Forest.


Friday, December 08, 2017
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