I live in a region where the ancient topsoil is under about 100 feet of clay that was deposited during a massive flood event 10,000 years ago. I tried for decad

I live in a region where the ancient topsoil is under about 100 feet of clay that was deposited during a massive flood event 10,000 years ago. I tried for decades to amend the soil by tilling in huge amounts of organic material to no avail. It had no affect. Eventually I ran across an explanation that it is impossible to change the structure of clay soil in that way. Clay soil is made up of extremely fine soil particles. The tiny particles don’t become bigger by adding organic material. Even if every single tiny particle was completely surrounded by organic material (an impossible feat), the original particles would still be tiny. They would fall through the larger organic material like water passing through and clump back together. As the organic material decomposes, the tiny particles will clump back together. Eventually you are right back where you started.