300 yr old RI timber frame Colonial in need of ideas to increase floor strength

[Don P]

The part of that plutonic rock poking its head up here is called cranberry gneiss, a metamorphosed granite. When I look at it for foundation purposes I put it in the foliated rock group in the strength tables. 600 million years away from here, the next ridge over that I'm looking at out the window, is dolomitic limestone, that was crudely quarried, first from the riverbeds. We weren't really settled until the period you are talking about though. Yeah, geology can get one into all kinds of discussions :D

[SwampDonkey]

The vast Canadian shield is granite, that what's left when the glaciers take everything off and move it south. :D

Around my local area it is not granite bedrock everywhere, it is calcareous shales mostly. Some pockets of granite around though, as it is quarried for riprap. But on top is granite stones dropped off by glaciers from northern regions where the ogres roam. Southern New Brunswick is sandstone mostly and shales as it was all under water millions of years ago. In my area to, the sea came inland for miles along the Saint John River and up the Tobique River. Where there is more elevation here there is granite. The top of Mount Carleton, for instance, is the highest peak here in the Maritime provinces and is granite.

Braithwright and Gagnon wrote up the geology of New Brunswick in the 19C and has since been updated and improved upon by successors. Only report I have on it comes from 1984 from the Geological Survey of Canada. It was part of university studies on geology when I was in the University of New Brunswick.

When you have glaciers, you sometimes have stuff on top that ain't at the bottom. :D

[D L Bahler]

Thanks for all that, swampdonkey. It's a real pain for all the farmers you know!

Our bedrock in Indiana is mixed sedimentary bands of Limestone, sandstone, shale, slate, gypsum, and others. Any other stone is mixed glacial deposits, and we've got a lot of that. Our part of the state is one of the flattest glacial tills in the world, and our limestone is some of the finest in the world. Most of D.C. is built out of it. Easy to work and weathers very well. 
Not too far from where I live, it sits a whole 18" under the surface. Lot's of stone quarries in these parts.