Malone Posted May 3, 2018 Share Posted May 3, 2018 Hi everyone! I found this fragment and it seems different than the usual inoceramus shell fragments I find. I was wondering if anyone recognized what it might be? Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 Also I found this piece that appears to have overlapping pieces sort of like scales. Link to comment Share on other sites More sharing options...
Cowboy Paleontologist Posted May 3, 2018 Share Posted May 3, 2018 I can tell that the first is an inoceramid, but I don't know enough to tell you more. The second one, I have no idea 1 Link to comment Share on other sites More sharing options...
Heteromorph Posted May 3, 2018 Share Posted May 3, 2018 Agreed, the first one is part of an inoceramid. Could the second one be a chunk of calcite, aka slickenside calcite? Does it feel like it’s crystal? Wash it off and put a little bit of vinegar on it. If it is calcite it will fizz. Here is a chunk from the lower Coniacian/ upper Turonian. 1 Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 29 minutes ago, Cowboy Paleontologist said: I can tell that the first is an inoceramid, but I don't know enough to tell you more. The second one, I have no idea I thought the bundled stacks was similar to inoceramus but the shape doesn't seem to fit with any inoceramus I have ever seen. The second item has a similar surface to the slickenslide but has a stacked bundle type shell material on the bottom side. It's too dark for me to take pictures tonight, but I will take some in the morning. Link to comment Share on other sites More sharing options...
DPS Ammonite Posted May 3, 2018 Share Posted May 3, 2018 The first photo is an Inoceramus hinge see: https://ukfossils.co.uk/inoceramus-bivalve-hinge/ The calcite needles normal to the shell are diagnostic for Inoceramus and the stacked parallel short line indicate the hinge. 2 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 That makes sense to me about the hinge. This other piece must be a really huge inoceramus then, because it's 7" and shows almost no curvature at all. Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 10 hours ago, Heteromorph said: Agreed, the first one is part of an inoceramid. Could the second one be a chunk of calcite, aka slickenside calcite? Does it feel like it’s crystal? Wash it off and put a little bit of vinegar on it. If it is calcite it will fizz. Here is a chunk from the lower Coniacian/ upper Turonian. You correct! Thank you! I am constantly amazed at how much knowledge there is on this forum! Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 9 hours ago, DPS Ammonite said: The first photo is an Inoceramus hinge see: https://ukfossils.co.uk/inoceramus-bivalve-hinge/ The calcite needles normal to the shell are diagnostic for Inoceramus and the stacked parallel short line indicate the hinge. Thank you very much! You are correct! I am very impressed! Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 11 hours ago, Heteromorph said: Agreed, the first one is part of an inoceramid. Could the second one be a chunk of calcite, aka slickenside calcite? Does it feel like it’s crystal? Wash it off and put a little bit of vinegar on it. If it is calcite it will fizz. Here is a chunk from the lower Coniacian/ upper Turonian. Here's a side picture that seems to show inoceramus calcite needles. I am curious if there was a situation where slickenslide could apply in conjunction with shell material? Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 Or are the calcite needles something that happens separate from the shell formation of inoceramus? Link to comment Share on other sites More sharing options...
Heteromorph Posted May 3, 2018 Share Posted May 3, 2018 (edited) On 5/3/2018 at 8:05 AM, Malone said: You correct! Thank you! I am constantly amazed at how much knowledge there is on this forum! Well, I was halfway right. The piece is calcite, but it is not slickenslide because... On 5/3/2018 at 9:56 AM, Malone said: Here's a side picture that seems to show inoceramus calcite needles. I am curious if there was a situation where slickenslide could apply in conjunction with shell material? The prismatic calcite crystals in the inoceramid shell were formed when the shell was formed. Slickenslide was formed when, long after the rock was deposited, surface water seeped through cracks in the rocks depositing their minerals and forming wedges and veins of calcite. A good way to tell whether you are looking at slickenslide or a piece of inoceramid shell is to look at the striations on the calcite. In your last picture you can see that the striations (i.e. prismatic calcite crystals) are very uniform in width while the striations on the slickenslide shown in my pictures can vary quite a bit in width because they were formed by geological processes. Another good way to tell is the fact that on your inoceramid shell the prismatic crystals are bracketed at the ends by smooth, flat sides, indicating the interior and exterior of the shell. You will never see that on slickenslide. This might help: Inoceramids Edited May 4, 2018 by Heteromorph See ynot’s rebuttal below. 1 Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 1 minute ago, Heteromorph said: Well, I was halfway right. The piece is calcite, but it is not slickenslide because... The prismatic calcite crystals in the inoceramid shell were formed when the shell was formed. Slickenslide was formed when, long after the rock was deposited, surface water seeped through cracks in the rocks depositing their minerals and forming wedges and veins of calcite. A good way to tell whether you are looking at slickenslide or a piece of inoceramid shell is to look at the striations on the calcite. In your last picture you can see that the striations (i.e. prismatic calcite crystals) are very uniform in width while the striations on the slickenslide shown in my pictures can vary quite a bit in width because they were formed by geological processes. Another good way to tell is the fact that on your inoceramid shell the prismatic crystals are bracketed at the ends by smooth, flat sides, indicating the interior and exterior of the shell. You will never see that on slickenslide. This might help: Inoceramids Absolutely awesome! Thank you for giving your time to help me understand! Link to comment Share on other sites More sharing options...
doushantuo Posted May 3, 2018 Share Posted May 3, 2018 Inoceramid calcite is LMC(Low magnesian calcite) and prone to diagenesis. The extent of the original mineralogy can sometimes only be determined by trace element or cathode luminescence examination 1 Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 2 minutes ago, doushantuo said: Inoceramid calcite is LMC(Low magnesian calcite) and prone to diagenesis. The extent of the original mineralogy can sometimes only be determined by trace element or cathode luminescence examination Do you know if this indicative formation of calcite is the only known formation of solely inoceramus shell ? Link to comment Share on other sites More sharing options...
doushantuo Posted May 3, 2018 Share Posted May 3, 2018 another way bivalve calcite prisms get distorted: 1 Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 4 minutes ago, doushantuo said: Thank you very much! It will take me awhile to digest this information because my vocabulary is so limited. I appreciate your knowledge and effort! My hope is that in helping me to understand you will also be helping others! Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 17 hours ago, DPS Ammonite said: The first photo is an Inoceramus hinge see: https://ukfossils.co.uk/inoceramus-bivalve-hinge/ The calcite needles normal to the shell are diagnostic for Inoceramus and the stacked parallel short line indicate the hinge. I have a question about the hinge pertaining to the edges on each side of the hinge. They are extremely thin. The calcite needles on either side are less than 1/8". That would seem to make the actual shell paper thin. With the line parallel to the edges showing the direction of the hinge wouldn't that make the shell fairly large and to big to be that thin? Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 How straight the line is would seem to indicate a large bivalve. Link to comment Share on other sites More sharing options...
Malone Posted May 3, 2018 Author Share Posted May 3, 2018 Unless it was shaped like a hotdog Link to comment Share on other sites More sharing options...
DPS Ammonite Posted May 3, 2018 Share Posted May 3, 2018 36 minutes ago, Malone said: How straight the line is would seem to indicate a large bivalve. Some Inoceramus were huge - over 5 feet: https://en.m.wikipedia.org/wiki/Inoceramus It is thought that their large area and thin shell helped them float on the soupy muddy bottom where there was little oxygen and competition for space. 1 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
Malone Posted May 4, 2018 Author Share Posted May 4, 2018 I found another piece that shows an extremely thin shell, but the shape on, what I assume to be the top side, is not ribbed nor smooth. Am I correct in assuming that if I find the calcite needles stacked that it is a inoceramus or retroceramus shell fragment of varying species? Link to comment Share on other sites More sharing options...
Malone Posted May 4, 2018 Author Share Posted May 4, 2018 Here's an example. This is a fragment that when was approximately five inches. It broke almost in half while handling. I had a hard time getting the camera to focus on the ver, It is the same stacked calcite formation as the others. Link to comment Share on other sites More sharing options...
doushantuo Posted May 4, 2018 Share Posted May 4, 2018 Link to comment Share on other sites More sharing options...
ynot Posted May 4, 2018 Share Posted May 4, 2018 10 hours ago, Heteromorph said: Slickenslide was formed when, long after the rock was deposited, surface water seeped through cracks in the rocks depositing their minerals and forming wedges and veins of calcite. This statement is wrong. Slickensides are a feature of faulting where the rocks slipping past each other leave gouges on the contact surface. Later, the rocks can separate and fill with other minerals which can make a cast of the slickensides. 2 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
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