Guan Ying Ge boulder clay was rediscovered when road workers cut through a part of hill.  It was formed during Da Gu Piedmont glaciation period 0.9～1.1 million years ago. Piedmont (French for foot of the mountain) is a geological phenomenon formed by massive amounts of ice deposits that ended up at the foot of the mountains during glaciations.  They caused vast plains and depressions which sometimes developed into lakes.  Imagine a road crew bringing to life a part of our earth history!