brachiomyback Posted June 13, 2009 Share Posted June 13, 2009 My job brought me to Nashville Tennessee three times over the past year. I ended up being able to squeeze in a couple of hours each time after work on a hillside of an Upper Ordovician Period Leipers Formation (Maysville Group) that was deposited approximately 445 million years ago. I made correspondence with an area high school geology teacher who was kind enough to recommend one of his sites that he takes his class to. The formation was accessed on foot by crossing a gated roadway that led downhill to this exposure. The site was secluded other than the hum of traffic just over the upper cliff top. The cliff sides, in general, were accessible; however had some pretty steep drop offs / sheer walls. Definitely made sure I had my cell on me. “Slid” down a couple of times and skinned up my hands / forearms trying to reach that “elusive” fossil. On my second and third trips I came prepared with the correct gear…. steel-toes boots, fingerless gloves, Carhartt jacket and the most important, my pick mattock. That piece of equipment made my subsequent trips all the difference in “extracting” my finds. My first and second trips were last fall and it was great being in the outdoors with the awesome fall scenery. I even “kicked up” a couple of deer on the way to the site. My last trip was this spring and I was amazed what six months of weathering could do to the strata. There were even shear walls areas where large sections succumbed to gravity. It resulted in me looking up more frequently and quickly passing said areas as I meandered along the formation. A hard hat wouldn’t have helped in this situation. I found a good assortment of upper Ordovician Period fossils, mainly brachiopods with primarily Platystrophia, some Rafinesquina and a handful of Hebertella, a few gastropods, various bryozoans and a couple of Streptelasma (coral). I tried one other site and the only thing I found is what I believe is a cephalopod partial (Stones River Group). Among all of the grey limestone of the Leipers Formation, you will find a white rock, gypsum (calcium sulfate). Gypsum is an evaporite which forms only under conditions of very high salinity. Some of the gypsum forms nodules in pockets in the sediment. These conditions occur in hot climates, in areas separated from the main sea, where evaporation makes the area very saline. Under these conditions, calcium sulfate becomes supersaturated and crystallizes out of solution. Mineralization therefore can occur when the hollowed out centers of fossils, such as brachiopods, are geodized or completely filled with calcite. In many ways, the mineralization of these hollow fossils resembles typical Midwestern geodes. The sun definitely helped make finding the geodized brachiopods easy, like diamonds in the rough. The fossil collecting was therapeutic and I didn’t want it to end, but soon the evening shadow was cast over me. enjoy… - Brad Link to comment Share on other sites More sharing options...
tracer Posted June 13, 2009 Share Posted June 13, 2009 very well written. good post. Link to comment Share on other sites More sharing options...
RJB Posted June 13, 2009 Share Posted June 13, 2009 Yeah, good story Brad. Lots of info to. Im not much one for crystals, but now that I see some associated with fossils, that makes it much more interesting. Nice finds RB Link to comment Share on other sites More sharing options...
Auspex Posted June 13, 2009 Share Posted June 13, 2009 Outstanding trip report! Nice fossils. and the paleoecology lesson is a much appreciated bonus. (I can almost smell the rock...) "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
Traviscounty Posted June 13, 2009 Share Posted June 13, 2009 Nice stuff Brad. Very informative post. Link to comment Share on other sites More sharing options...
mommabetts Posted June 13, 2009 Share Posted June 13, 2009 Loved the detailed story of your adventure of fossil hunting, thanks for sharing. Those are some very nice brachs with the crystals in them. Link to comment Share on other sites More sharing options...
Seldom Posted June 13, 2009 Share Posted June 13, 2009 Great story like that site pic looks like a interesting place to hunt. I for one like crystals have more crystals then fossils. Hope you get back there soon and keep us updated Galveston Island 32 miles long 2 miles wide 134 bars 23 liquor stores any questions? Evolution is Chimp Change. Life is not about waiting for the storm to pass; it's about learning to dance in the rain! "I like to listen. I have learned a great deal from listening carefully. Most people never listen." Ernest Hemingway Link to comment Share on other sites More sharing options...
Shamalama Posted June 13, 2009 Share Posted June 13, 2009 Very good post! I loved the way you included all the aspects of visiting a site. I need to improve my writing skills so that my writeups are as good as yours. Nice geode finds too... does the Leipers Formation correspond to the Grant Lake formation of northern Kentucky? The fauna and geodes sound very similar. -Dave __________________________________________________ Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPheeIf I'm going to drive safely, I can't do geology. - John McPheeCheck out my Blog for more fossils I've found: http://viewsofthemahantango.blogspot.com/ Link to comment Share on other sites More sharing options...
brachiomyback Posted June 14, 2009 Author Share Posted June 14, 2009 I'm not familiar with the Lake Grant Formation; however funny you mentioned Northern Kentucky. I had some time to "pick" away at a Kope Formation site about 3 months ago in addition to a proximate site whose formation was "well above" it. I didn't know what formation it was but it was very similar, could have been the Grant Lake Formation. It produced much better Rafinesquina specimens though and I didn't find as much geodized brachs. I'll post that trip report next. FYI...... a good site(s) for reference if you guys haven't checked them out yet....... http://www.uga.edu/strata/cincy/strata/Lit...atGlossary.html http://www.uga.edu/strata/nashville/strata...ratigraphy.html - Brad Link to comment Share on other sites More sharing options...
Shamalama Posted June 14, 2009 Share Posted June 14, 2009 Great link, I spent a hour going through all the species. -Dave __________________________________________________ Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPheeIf I'm going to drive safely, I can't do geology. - John McPheeCheck out my Blog for more fossils I've found: http://viewsofthemahantango.blogspot.com/ Link to comment Share on other sites More sharing options...
Nicholas Posted June 14, 2009 Share Posted June 14, 2009 Very nice specimens I have quite a few very tiny fossil geode brachiopods, and a few fully crystallized brachiopod molds. My favorite specimen of that nature is a horn coral I have which is crystallized all over the outside it just looks wonderful. Your knowledge of geology has been very helpful to me, I learned quite a bit. A+ post. Link to comment Share on other sites More sharing options...
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