The soil here is mostly water-deposited silt, sand, clay and gravel, covered with windborne silt or loess .
(The soil here; is mostly; water-deposited silt, sand, clay and gravel) (clay and gravel; covered; with windborne silt or loess)
The soil here clay and gravel
is mostly covered
water-deposited silt, sand, clay and gravel
with windborne silt or loess