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Showing results for tags 'calcareous'.
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I have another oddity here. Found on a Tampa Bay beach in Florida. It is about 3 inches long, brittle but light weight and hollow, with one end open and one end sealed. The side hole or spout attaches to the larger opening. I did some research and it resembles a calcareous sponge. Is it a sponge? Is it a fossil or modern? Thanks as always to a great group of people! Please see 5 pics below.
I suppose these are boring to most people but they have piqued my interest as of late, when I started noticing how many of them there are and how consistent their form. It appears as a trough-shaped thing made of carbonate, lighter than the surrounding black shales. These shales (Haslam Fm, Upper Cret.) are full of odd blobs and lumps and tube-shaped things that I have always ignored, assuming they were non-fossil, but they don't seem to work as burrows or concretions either, and considering the possibility of calcareous algae and the like, I started to wonder. (Do burrows ever have a U-shaped cross-section, and why would they have a lighter, calcareous appearance?) This one is not the best example, I need to pick up more when I see them, but hopefully you can see what I'm looking at. There are some lumpy, grainy shapes as well: Possibly a (sideways) U-shaped cross-section on the end here too but it is faint. Lots of variety of shapes aside from the usual roundish concretions, many nondescript but some recurring patterns among them such as the above. They all have a calcareous/carbonate composition (I assume from the lighter color). Any opinions? Biogenic or not? What would account for the formation of this long trough shape in particular? I will make a point of picking up more/better samples and add them here.