Prehistoric forest?

Is it a bird, is it a plane, or is it a... prehistoric forest? 

I'm pretty sure it's not a bird or a plane, this milky grey-green, lumpy bumpy, squidgy under foot ground growth that has appeared on Takapuna beach after a serious storm some months back drove several layers of sand further up the beach to expose it. And exposed it has remained.

People are talking, as they will about the appearance of something before unseen, and what they're saying is that it is the remnants of a prehistoric forest, which is kind of cool. I like the idea, even if I don't much like getting the prehistoric forest in my shoes. It's kind of sticky, is the prehistoric forest. 

And it is now, maybe three months hence, dissolving, seemingly, and in the process, is turning the edge of the beach water a milky grey-green, which you can sort of see in this picture that I took yesterday. It's greener than this shows and quite attractive really. 

But if anyone out there knows for sure what it is and what the longer-term prognosis for our would-be prehistoric forest and beach might be, I would be most interested to find out. 

Regards from a curious prehistoric forest frolicker,

Sacha