Devonian-Silurian Paraconformity

Recently, a friend gave me a copy of a book written by some local professors entitled Ancient Animals Locked in Louisville's Rocks: A Guide for Fossil Hunters.  The book was published by University of Louisville Printing Services in 1995.  It is out of print now but one can find it for sale used on the Internet at times.

The book is written is a nice style for amateur geologist/paleontologist. It covers the four periods of Louisville's exposed geology: Ordovician, Silurian, Devonian, and Mississippian.  Each section discusses the period, fossils found there, formations and a road trip guide.  The Silurian section takes about a place in Louisville one can view a paraconformity.  Described in the book as place in the rock which appears to be seamless boundary between two time periods but on closer study sections of geological layers are missing.  In this case the boundary is between Silurian and Devonian rock.  The Upper Silurian and Lower Devonian Periods are missing (25 million year gap -- 422 to 397 million years ago).
The layers shown are Louisville Limestone covered by Jeffersonville Limestone.  Image below is of Halysites coral colony which is the index fossil for Silurian Period.

The location to see the paraconformity is off the sidewalk coming from Grinstead Drive and going up the hill on Lexington Road.  I found the Silurian Period fossils but was having trouble seeing the Devonian layer.

Some sort of coral layer.

This last image has a number of branching corals and one brachiopod.  The one branching coral reminds me of a Devonian Thamnoptychia.  The brachiopod does not look familiar though.

Portable Diamond Saw

After reading this Trilobite Tale web page, it inspired me to modify my own gas powered trimmer with a diamond blade.  The blade is one that was used on a tile saw that I also use to cut fossil matrix with.  The attachment used is a brush cutter which had its blade replaced.  As always, WEAR SAFETY GLASSES when cutting or trimming with this type of power tool!  Follow the directions that comes with the power trimmer as well.

I set up the hose to spray water on the rock as I cut it. The pictures of the rock did not turn out since it was getting dark.  The blade was not centered on the shaft so it wobbled.  I need to find a way to correct this.  Also one need to press down against the rock or the blade will bounce.

The blade guard need to be replaced with one that will allow more blade exposure.  The blade being used is 7" in diameter.  Once I have made some changes I will post more results from this project.

Picture of original brush cutting attachment.  It took a while to figure out how to remove the blade.  One needs to attach a C-clamp to the drive shaft and then hold with their foot.  Take a racket with in this case 0.5" socket to remove the bolt hold the blade.

Phacops Trilobite with Tentaculites

This plate was recently sand abrasive cleaned.  It revealed the cephalon of a Phacops rana (Green, 1832) trilobite with a Tentaculites (Schlotheim, 1820) in front of it.  The Tentaculites (Schlotheim, 1820) was in between a broken segment of Phacops (Emmrich, 1839) thorax.  Further exploration of the plate reveal pieces of unidentified bryozoan and Protoleptostrophia (Caster, 1939) brachiopod.

Matrix is Silver Creek Member of North Vernon Shale Limestone of Clark County, Indiana.  Fossils are from the Middle Devonian Period (Eifelian) dating approximately 397 to 391 million years ago.

Unfortunately, I did not take a picture of the plate before I cleaned it.  Curses!