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Showing results for tags 'columnals'.
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What is the difference between crinoid and blastoid columnals. I know the difference between the calyx of a crinoid and the theca of a blastoid. I have a site I visit that has a mash up of both calyxes and thecas, but not with attached columnals. It is a Mississippian site, Warsaw formation.
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I know how Crinoid columnals looks like, but which are the features of other echinoderm classes (Rhombifera, Diploporita,...)? Image of a crinoid columnal mould (scale bar 5mm).
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Crinoid columnals from Devonian Keyser Formation in Pennsylvania
traveltip1 posted a topic in Fossil Hunting Trips
I collected some crinoid columnals and a horn coral....weathered from the Devonian Keyser Formation limestone in Pennsylvania. As usual, preservation is not very good. -
Hello, I have many crinoid columnals that I collected in gravel (I suppose it was river/creek gravel collected and sold by a "sand and gravel" company) in Illinois many years ago. I have two questions that may be obvious to more seasoned fossil hunters/students. 1) Exactly how did the crinoids actually grow, meaning, how did the stems' diameter expand horizontally in size as time went on, since the stems were mostly composed of hard calcium carbonate/lime. In other words, it seems that once they are "hardened" or "frozen" into a certain size, how can they get bigger? Was there growth tissue on the OUTSIDE of the stem that kept adding on calcium to the inside, like tree trunks creating wood and bark? (I can understand the growth of whorled type seashells, but I can't get this through my head.) 2) Many of the columnal discs/segments I have found are virtually solid silica, some with a glossy almost pearly luster, I suppose would be classified as flint, chert or chalcedony. I assume from what I've read that this is from replacement of the original calcium with silica over a long period of time. This may seem simple-minded or thinking too deeply, but do researchers claim to understand how the silica could actually have "moved" or migrated into the spaces where the calcium used to be? I can't visualize how this would be possible. Like, one molecule at a time gradually moves through solid rock? Does anyone understand why this seems so hard for me to visualize? Or is this believed to occur because the original calcium actually changes it's molecular characteristics without moving? Any input or comments would be greatly appreciated!
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These columnals can be quite common. Some are smooth, some warty.
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