We bought this place because it was already treated organically by the people we bought it from. So I have rather nice soil, in untreated areas it is dark loamy, sandy soil. I have to dig down 2-3 feet to get into the sand..

I consider myself lucky.. I'm just curious... How far do you have to dig down until you hit shale, just sand, or just rocks? Where I grew up.. the soil in our garden was a combination of light brown soil, some sand would have been nice... there was a clay, blue to gray clay, component to it. It held water better than this soil I have here. (the clay?) But it wasn't as nice and dark as the soil I have here.
We only had to dig down a foot to 18 inches to hit "the hard stuff" like shale, raw sand, and hat clay mixture.

SINce I have been lasagna gardening, I have been planting in more or less decomposing leave matter. But in the big plot that has been amended with leaves almost every fall, ie, the leaves were laid over the area, then tilled in every spring... the soil is nice and dark, sandy, but if I really want to dig, that is where I have to go down 2-3 feet to hit the solid sand rock layer.

I'm amending, I'm amending... using rabbit cage bedding, food scraps and leaves, even getting leaves from other folks. So don't get on me about not amending.. FGS!

I have been in this place 20 years, I have been putting the leaves back every year into one area or another.. No leaf bags on the curb at my place. I have also been keeping rabbits for 18 years and putting all their droppings out there. Just curious

I moved here (North Delta B.C. just south of Vancouver) 4 years ago and have been gradually converting the back yard into a garden. I only have to go about 4-6 inches to hit garvel and sand. Hopefully in 20 years it will be 18 inches.

DH has been digging holes for posts, just black dirt all the way. I believe we are sitting on old farm ground.

While breaking ground for my new gardens, I found a horseshoe!! Intact, but rusty.

I only have to go 6 inches or so in most spots to hit hard red clay.

The clay is nutrient rich though, so most of my amending (I dig out the new bed, literally pulling out the clay, mixing it with compost, manure, and maybe some peat moss--once I did sand, but I'm not sure it was worth the cost and effort, so I haven't done that this year) is more to even out the ph (it's acidic clay) and to make it much more workable.

I use mostly a modified version of square-foot gardening, but do the same for the open areas (this year, for corn and strawberries--and a smaller area I have that was bush beans last year and has lettuce and onions this year. When it gets too hot for the lettuce, something else will go there.)

Generally the top 6 to 8 inches of soil is what you are interested in, although over time soil below that level will get organic matter mixed in and sometimes the longer OM is added the deeper it will be in the soil. However, since the aerobic bacteria are most active in the top 6 to 8 inches that should be your primary concern.

All of the flower/vegetable beds have converted over time (I've been here 18 years) and I can dig about two feet down with a trowel.

But the uncultivated areas show what things were like before the gardens. Just under the sod (about 3 inches of root/soil mix) is the rocky dirt. You can't dig any deeper without hitting big chunks of rock.

No sand, no rocks, no shale. Just heavy clay. 20 years ago I double dug down 2 feet in all the vegetable beds, and it was only clay. Nowadays I wouldn't do all that digging; I would lasagna instead.

All I have to do to hit sand, is step out the door. no digging involved at all. Lots of amending in my future.