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I e-mailed these pictures to a geologist I know and at first she thought the stridations on this boulder might be from erosion. But as you will see in one of the pictures I post - the lines are running in opposite directions in areas that are concave. The striations "wrap around" this boulder - so although it looks like seashell-type marks, the shells would have had to have been huge as they go completely around the boulder (though admittedly, I couldn't check underneath it). The area is in New Mexico in the Santa Fe Group, Miocene Epoch (7-25 million years ago), with some pliocene patches, but is known to have had boulders wash down from the nearby Sandia Mountains, which go back to the proterozoic period. This area is at the northern end of the Sandia Mountains in the foothills. "Fossils of marine life such as brachiopods, crinoids, fusilinids and corals are evident in some of these boulders." All the fossils I have been able to identify in this general area have been sea life fossils, such as columnal crinoids, brachiopods, fusilinids, possibly an ammonite, and some possible worms. Click to make larger... The watch face is hazy with a worn bezel because it is scratched from carrying rocks (I wear it inside my wrist) - and I use a newer one for scuba diving (one that I can see ). This photo shows one side that is flattened with shell-like striations - but it is the only flat area; After going back and taking more photos, I think I found the striations cannot be due to erosion, because in this concave area they actually go in diametrically opposite directions. Anyone have any better ideas about this boulder? I have more pictures I can post if it might help.

Lately if you have seen some of the topics I've started, these trips revolve around an Ordovician reef I came across by the Credit River in Mississauga, Ontario. One of the few things I discovered while exploring these spots is that there are plenty of Stromatocerium sponges which I red is a stromatoporoid. My question is, can anyone lead me to any papers about the growth forms of Ordovician stromatoporoids? I have found specimens of stromatoporoids and from the way I see it, some of the specimens I found of the same species have different growth forms. Some have those things they call monticules on the surface, and some don't exhibit them at all. Instead these specimens exhibit cracks and splits on the surface of the organism with irregular bumps and overgrowths. I'd like to know what causes this. Some of these sponges, from what I have collected, colonize some pieces of Prismostylus on the top.

Hi, I was wondering if anyone had any thoughts on the ID of these fossil structures. They're found in a fossil patch reef of Bartonian age in Northern Spain, at the moment I am exploring the possibility that they could be very large oysters of some kind, they could possibly be stromatoporoid fossils though (however they don't have any obvious internal layering or structures). Other fossils nearby include small oysters and solitary and colonial scleractinian corals, along with large nummulitid foraminiferans. The layered fossils were very hard, and I was not able to take any samples, interestingly they did spark in contact with a hammer, could this be due to silicification? One of the nummulites also had a shiny metallic luster. Hope some of that helps, thanks in advance for any help.

I have four specimens that could be the same thing, but the appearance is different enough so that I decided to go with separate posts. They came from glacial till in north eastern Maine. The age is most likely upper Ordovician - Lower Devonian, and almost certainly they are marine. My first thought was Stromatoporoid, but they seem a bit too weak in the stromato to me. What do you think ?