Fossil or Pseudofossil?
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image 1 image 2
The fossil measures 8 mm x 6 mm
Click Here Original Large (unedited) picture of image 2
Images captured with a Dino-Lite digital microscope
This specimen was found in central Colorado in the Pennsylvanian Minturn Formation.
The Minturn Formation contains mostly near-shore marine deposits, with typical late
Paleozoic invertebrates. This specimen was found associated with brachiopods,
crinoid stems, gastropods, and echinoids plates.
I have been trying to decide if this is a fossil or not. If it is a fossil, I would appreciate
help with determining what kind of fossil it is.
1. Possibly a tiny weathered echinoid or crinoid plate with visible bumps at 12 O'clock to 5 O'clock.
2. My opinion - not a fossil. More along the lines of a small septarian nodule cut in half.
3. It could be a remnant "pond" of original evaporitic calcite or gypsum(?) lamina, or an in-filling (replacement) of original (evaporitic?) lamina introduced during the course of sediment de-watering or later diagenetic processes.
Some "rivulets" of the same(?) mineral(s) appear to flow into-or-out from the "oval pool's northern shore." Because the mineral appears to be more resistant to weathering than the limestone(?) matrix I will suggest it is not gypsum or calcite; though possibly aragonite; but more likely barite, strontianite, or a layered encrustation composed of more than one mineral.
Microbial colonies, including stromatolite-builders, inhabit many environments, including ancient sabkha-type marginal-marine depositional systems evident in the Minturn Fm. strata. It seems possible to me that it may be a fossil of a microbial colony preserving original dessicated "sun-cracked" surface texture.
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