stratigraphy in my backyard

Again, an amateur request for help.

Can someone steer me in the right direction to determine the age of a layer
of limestone in a creek-cut hillside in my backyard?

Being in Cincinnati, I know I am near (but not too near) the Cincinnati Arch
of Ordovician layers.  I don't know the fossils very well.  This particular
formation is about 15-20 cm thick and lies between much thicker layers of
soft clayey shale of medium gray with very few fossils.  This is in a
drainage area to the Little Miami River maybe ten miles north of its mouth
on the Ohio.  I am thinking it is much less old than 450 MYA...but how much?


I am guessing that for most of the period while this rock was laid down was
turbid and muddy: the clayey shale.  There was a period of clear water with
a prolific marine environment: the high density of shell debris and other
fossils in the limestone.  Am I close?

The coolest thing, though, is that the under-surface of a large rock I
pulled out of its position in the cut has these great casts of indented
trails made by some crawling thing ...how long ago?  So, I am thinking that
these trails occurred at the transition from a muddy swamp or something to a
clear water environment at that time.

What is the best approach to solve this puzzle?  I suppose I could lug the
rock down to the Univ of Cincinnati Geology Department...what would they ask
me regarding the original location? anything else I should tell them?

Thanks very much for understanding my enthusiasm and for looking past the
lack of training!