Re: stratigraphy in my backyard

[EMAIL PROTECTED] wrote:
> 
> 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!

Alas, it was once my backyard, too.
Unfortunately, I don't remember it anymore.
You need as localised of a strat column that you can get.
Copy & paste the following into Google:
ohio "stratigraphic column" cincinnati