During geology time, large masses of land are raised above sea level. Erosional forces wear these down, depositing the material in low
places usually filled with water. Such regions may then themselves be raised forming mountains erosional process is repeated.
Three distinct layers of sedimentary material carried from high regions to the west were deposited over southern Saskatchewan during the
cretaceous period (60-130 millon years ago). The first of these often exceeds 1100 feet in thickness. The second layer shows a transition
from marine to fresh water. It is characterized by rusty greenish to yellowish siltstones, sandstones and mudstones. The upper layer is kaolinized.
The third layer is non marin and varies from 0-45 feet in thickness. The white kaolinitic material with grey to black carbonaceous
layers make it easy to recognize. It is exposed in the valley near Castle Butte.
During the Paleocene, a layer up to 500 feet thick was deposited. It is characterized by coal beds, non marine sands, shales, silts and clays.
Where exposed on a cliff face the lower edge is grey in color and is called the "grey facies". The upper layer is brownish often containing
white kaolonitic. This later is called the "buff facies".
The ice age changed the face of this area. To the north the ice sheets were much thicker but to the south they were none existent.
The Big Muddy is a melt water channel which carried vast quantity of water eastward.
Sediment was deposited forming deltas of fine silt
and sand. Terminal morraine, ground morraines and hammocky form the major landscape characteristics around the valley.
In recent periods erosion has served to round the hills, cut channels, and in general deposit material in the valley. This results in an
area of interest to the professional and the sightseer.