Calcitic vs. Aragonitic shells in molluscs. Information appreciated.

[Ludwigia]

15 hours ago, Canadawest said:

 

 

 

A whole bunch of stuff can happen. What minerals are washing through the deposits, etc.  Carbonates, calcite...?  One weird thing that happens when there are distinct sedimentary layers is that minerals of young layers of fossils can seep into underlying older layers. This can 'mess up' trying to age material unless the actual index foseils are known.  There can be a bit of a tension between old paleontologists that study fossils and geologists that use chemical analysis in aging deposits.

 

Of course . Or pyrit or opal or silica, or various ores, etc. can also replace. That's an interesting aspect you mention at the end.

[doushantuo]

something recent on mineralogical-taphonomic biases(or lack of them):

 

Jordan_015-Let.pdf

[PFOOLEY]

Figure 2. in this article...

 

Aragonitic rostra of the Turonian belemnitid Goniocamax.pdf

 

...has some electron images that may be helpful to you. 

 

 

 

 

[Ludwigia]

Thanks, guys.