Haynesville Sand

I realize I may be a little slow on the uptake, so if I have to come up with a legitimate excuse, I guess I'll chalk it up to turning 50 last summer.

Myabe this is an industry trade secret that the oil and gas companies are holding on to for dear life, but I was wondering if someone could describe for me in layman's terms what the Haynesville Sand (not Shale) is, and which parishes specifically (if known) does it cover? I have been told it extends across the entire breadth of the Ark/La line (Webster, Claiborne, Union, etc), but I cannot seem to find anything authoritative that would substantiate that.

So. can anyone shed light on this for me? Is it in Claiborne Parish, and if so, how far?

Thanks!