<P> Sedimentary environments can shift their geographical positions through time . Coastlines can shift in the direction of the sea when the sea level drops , when the surface rises due to tectonic forces in the Earth 's crust or when a river forms a large delta . In the subsurface , such geographic shifts of sedimentary environments of the past are recorded in shifts in sedimentary facies . This means that sedimentary facies can change either parallel or perpendicular to an imaginary layer of rock with a fixed age , a phenomenon described by Walther 's Law . </P>
<P> Sedimentary environments can shift their geographical positions through time . Coastlines can shift in the direction of the sea when the sea level drops , when the surface rises due to tectonic forces in the Earth 's crust or when a river forms a large delta . In the subsurface , such geographic shifts of sedimentary environments of the past are recorded in shifts in sedimentary facies . This means that sedimentary facies can change either parallel or perpendicular to an imaginary layer of rock with a fixed age , a phenomenon described by Walther 's Law . </P>
who formulated the principles describing the layers of sedimentary rocks
who formulated the principles describing the layers of sedimentary rocks
Walther
Walther