Superior Upland Geography of the Interior United States

brockway mountains of keweenaw peninsula, michigan (precambrian of keweenian series)

the superior upland province of laurentian upland projects united states west , south of lake superior. upland, part of canadian shield along adirondacks, deformed structure , composed of igneous , metamorphic crystalline rocks commonly associated rugged landscape. @ prehistoric period, had strong relief, today upland whole gently rolling inter-streams surfaces being plateau-like in evenness. here have altitudes of 1,400 2,300 feet (700 m) in higher areas, such misquah hills , huron mountains. in province, find part of ancient mountains regions initiated crustal deformation , reduced long continued erosion peneplain of modern relief. peneplain occasional moderately high monadnocks left behind during peneplanation of rest of surface. erosion of region must have been far advanced in prehistoric times, practically completed, because peneplain surface overlapped fossiliferous marine strata geological date, cambrian. shows depression of region beneath ancient sea took place after long existence dry land.

the extent of submergence , area on palaeozoic strata deposited unknown. because of renewed elevation without deformation, erosion in later periods has stripped off undetermined amount of covering strata. valleys uplands here , there trenched moderate depth appear be, in part @ least, work of streams have been superposed upon peneplain through removed cover of stratified rocks.

glaciation has scoured away weathered soils presumably existed here in preglacial time. left behind firm , rugged ledges in low hills , swells of ground , spread irregular drift cover on lower parts, whereby drainage disordered being deposited in lakes , swamps , elsewhere rushing down rocky rapids.