It contains varying amounts of gravel, sand, silt and clay that was deposited by the 
(It; contains; varying amounts of gravel, sand, silt and clay that was deposited by the) (varying amounts of gravel, sand, silt and clay; was deposited; by the)
It varying amounts of gravel, sand, silt and clay
contains was deposited
varying amounts of gravel, sand, silt and clay that was deposited by the
by the