Leaving for Missouri this morning, we headed east across the vast bed of a Cretaceous Sea, which stretched from Texas to British Columbia, some 100 million years ago. Along the base of the Front Range and out across the High Plains, the ancient bed is covered by a veneer of younger, Tertiary sediments, eroded from the Rockies as they pushed skyward. However, Cretaceous Pierre shale is exposed along the South Platte Valley, where the river has removed the overlying deposits; it is this marine sediment that enriches the soil and supports agriculture across the Colorado Piedmont.
Further east, in central Kansas, the Cretaceous sea deposits become more evident. There, throughout the post rock country from Hays to Russell, marine limestone lies near the surface, outcropping at road cuts and widely used to construct farm houses and to support barbed wire fencing.
By late summer, as the intense sun takes a toll on the Great Plains greenery, prairie sunflowers adorn the landscape. Rising in scraggly clumps across the High Plains, these wildflowers become more abundant on the lower, wetter terrain of central Kansas, where they blanket fallow fields and sprawl along stream valleys. More than offering welcome color to the drying plains, prairie sunflowers provide food for a wide range of grassland mammals, game birds and open country songbirds. For those of us driving across the semiarid landscape of the Great Plains, once occupied by a Cretaceous Sea, the bright yellow sunflowers are food for the soul as well.
