Thanks guys. It was just playing with extremes I guess; the sandy shader is an unclamped ridged one sized 10/1000/1, with a bit more contrast and slided a little towards the black. Noise buoyancy (whatever that really means) was 2, the variation -2, and a bit of warp. For the downward displacement of this pattern I included a color adjust shader with both black and white point upped. I also smoothed this layer I think.
I never actually thought about the variation, buoyancy, and clumping, never tested what it really did... more to do.
