These Lower Mississippian age crinoids were mined from a crinoid lens discovered within a ravine leading into Indian Creek during the early 1980s. The geologic unit from which they were obtained is called the Ramp Creek member of the Edwardsville formation. The crinoid deposit is characterized by being contained within an unusually thick bed of siltstone two feet in width. The crinoids were contained within the bottom six to eight inches of the bed, which also featured graded bedding, such that the upper portion of the layer was finer grained and devoid of fossils. I interpreted it to be an instantaneous deposit in which the crinoids were buried alive with their associated commensal fauna of platycerid gastropods and ophiuroid starfish.
Although many of the crinoids had stems attached to the crowns, many crowns were also found to have been detached from their stem. The difficulty encountered with excavating and retrieving slabs however from this layer limited the number of crinoids that could be retrieved with their stems intact. This deposit I informally termed the "blue lens", as I had found a brown lens of crinoids the previous day during a weekend excursion doing reconnaisance. I found these deposits after searching several known localities with friends, and then eventually exploring a portion of indian Creek that had no reported localities. I was also aided by a recently published manuscript on Crawfordsville crinoids done by Dr. Lane of Indiana University which I read thoroughly, and by the advice I had been given by a student of his, namely to search the ravines leading into the creeks of this area of Indiana. Indian Creek was a locality that I felt certain would have undiscovered crinoid deposits because the investigator of the area during the 1800s had died at an early age, and therefore it was unlikely that he could have explored the area very completely. This hunch proved to be correct, but soon afterward I was to find that others were hunting this area as well. The brown lens that I had found on a Saturday would later be taken over and mined by a known specialist within the area, and therefore I was very fortunate to be able to work the blue deposit which I had found the following Sunday without competition. Later I offered to clean and donate specimens from the deposit to the university that I was attending at the time during completion of my Masters thesis concerning the paleoecology of Ordovician Cincinnatian molloscs, however my offer was rejected by the equipment manager who controlled the use of the air abrasive machine. My thesis advisor welcomed my proposition, but this technicality eventually kept the donation from happening. Nevertheless, I did keep working this deposit and retrieving crinoids over the next two years, even after graduation and moving to Oklahoma. The crinoids were collected during day long excursions, with the aid of a helper at all times, along with the use of a large portable rock saw, shovels, pry bars, sledge hammers, drill bits, and of course, wedges. After a day of mining, usually a good portion of the deposit had been "sawed" out and excavated with the prybars and drill bits via sledges. It was necessary to always saw off the upper portion of the two foot thick silstone so that the bottom portion could be wedged out in lengths along the face of the exposure. The slabs and pieces that were excavated during the day were then carried to the car at the day's end. Usually it took at least three hours or more of driving each way to and from the locality, so days were long, and return visits were usually planned months later. I last visited and worked the locality during the mid 1990s. I did make a trip to this area much more recently though in 2016. That was when I learned that the property owners who used to allow me access no longer owned the property, and that it had been sold to the Indiana State Park System. Perhaps one day I will be able to show someone from the Parks department where the site is, as a portion of it still resides there. The deposit had a width of about 25 feet and the center of the deposit was still producing, just becoming more inaccessible due to increased overburden.
This portion of a large slab contains two Agaricocrinus splendens crinoid crowns along with the crinoid Pachylocrinus aequalis and the crinoid Abrotocrinus unicus and is only partially prepared. This is the bottom of the layer, and the last two pictures are the bottom of the overturned slab. The piece fits to a much larger slab that it was broken off of. It was mined during the month of August in 1982.
This is the crinoid Taxocrinus colletti that was collected ealt within the mining of the deposit, the crown being exposed approximately eith inches from the bottom of the layer, and excavated as a piece with only a portion of the stem unfortunately. Only two of the this species of crinoid were recovered from the deposit, the other being less than half this size. Taxocinus is reported to be rare within the Indian Creek fauna, and this deposit was no exception. the crown of this crinoid has only been cleaned with end tip of a Bic pen cap, and only the stem has been cleaned using an air abrasive.
The three crinoid crowns featured below are Platycrinites saffordi, which were always found as large sized individuals. They were also found normally without stem attached, and long lengths of stems were found associated but not attached to the crowns. Invariably a platycerid gastropod would be attached to this crinoid crown along it's side.
These are two Gilbertsocrinus tuberosus crinoid crowns
Below is a large Scytalocrinus robustum crinoid crown that features a broken and regenerated arm. The other crinoids shown are Cyathocrinites multibrachiatus, Macrocrinus mundulus, and Halysiocrinus nodosus.
This is a large slab containing the crinoids Agaricocrinus splendens and Onychocrinus ulrichi, along with a partial Onychaster flexilis ophiuroid starfish.
Take a look at our image gallery to learn more about our company and what we have to offer you.
Check out some of the interesting denizens of this locality and also enjoy the gallery of specimens within the virtual museum!
Like us on Facebook and get 10% off your next order.