Dag on willjo,more nice ones!Just a guess but I was looking in this book and I think your preform might be a transitional paleo piece they call a "cowhouse slough".The other mid/late archaic piece in the book called a Bascom is close too,but I am leaning more towards the cowhouse.Very nice finds willjo,got me envious up here,lol-HH
We find Bascom blades and I don't think it is a Bascom, here are two whole Bascoms and a broke one to compare. I do think it is paleo though and if you look at the first photo you can see what was an attempted flute and it did not go deep enough or it could be thinning flake and I am doing some wishful thinking.
It looks Paleo to me.I was thinking it might be a cowhouse slough type because it fits the size and under the description it says the base can be slightly convex and can be fluted or thinned.The closes I could find to it from your region anyway.Nice Bascom's!