Recently we were involved in a Soil Expedition that took us to the Eyre Peninsula (EP) of South Australia. Many people see the EP as the home of the calcareous (limestone) soils. However there are many areas, especially in the southern parts of the EP that are rather acidic and many are lighter sandy soils with often gravelly buckshot over subsoil.
Some farmers have taken to clay delving in these areas to increase water holding capacity of the root zone and to reduce the non-wetting effect on sandy soils.
There have been marked beneficial results from clay delving, however does come at a significant cost, with many farmers budgeting between $400-$800 per hectare. However many have seen profitable returns overtime from the process. There are certainly risks in not understanding individual soil types when delved. The depth is very important.

One thing to consider is to conduct a soil test on the clay you plan to bring closer to the surface. The last thing you want to be doing is bringing any undesirable soil issues closer to the surface, such as toxic levels of aluminium, boron, salinity, sodicity and high acidity.
A couple of hundred dollar soil test could certainly save you a lot more well in the future!