Pond Boss Forums POND CONSTRUCTION Soil questions Dark loose clay

https://www.youtube.com/watch?v=mJ2SeE_uNx8

I am in the middle of my core renovation and wanted to drain the lake to be able to dry up the leak in the dam. In doing so I cut a 10 ft trench and noticed that some of my clay is real dark and loose. So much so that the trench collapsed into itself. (see the section of the video that shows the wall fall in) SO, is this good clay, just not compacted? Is it just wet due to the leak? or is there such a thing as bad clay and not workable to reuse for the core? I have read on blue clay, but this is more a dark gray when most other sections is brown,....not red, or orange, but brown (and is most definitely clay).