Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION IX.7.2. Calumet
DISCUSSION: Sub-subsection IX.7.2 is noted for steep ridges of Keweenawan (late Precambrian) basaltic lavas and conglomerates, which rise several hundred feet above the adjacent lake and till plains. The ridges of the Keweenaw Peninsula are part of the Lake Superior syncline, which extends from northern Wisconsin to the tip of the Keweenaw Peninsula of Michigan.
ELEVATION: 850 to 1,490 feet (259 to 454 m).
AREA: 285 square miles (740 sq km).
STATES: Michigan.
CLIMATE: See subsection.
BEDROCK GEOLOGY: The Precambrian bedrock is primarily Keweenawan basalts and conglomerates, but also includes sedimentary bedrock, such as the Freda sandstone and Nonesuch shale (Dorr and Eschman 1984, Reed and Daniels 1987). Erosion-resistant conglomerates and amygdaloidal basalt form the steep ridges of the sub-subsection, between which veins of more easily eroded lavas are sites for lakes and wetlands. The Lake Superior shoreline also consists of rugged volcanic bedrock. Copper-rich lava flows, common on the Keweenaw Peninsula, were extensively mined. The Nonesuch shale also contains copper, but often in concentrations too low for profitable mining.
The bedrock ridges of the Keweenaw Peninsula and of Isle Royale are both part of the Lake Superior syncline, which extends from northern Wisconsin to the tip of the Keweenaw Peninsula of Michigan. Isle Royale, located at the northern end of the syncline, is treated as another sub-subsection because of its climate, which is even more strongly influenced by surrounding Lake Superior than that of Sub-subsection IX.7.2.
LANDFORMS: The steep ridges of exposed bedrock rise several hundred feet above the broad plateau of the adjacent Gay sub-subsection (IX.7.1). Steep slopes occur along the north face of ridges, and high cliffs occur on the south face. Narrow wetlands are found in many of the depressions between the parallel ridges of resistant conglomerate and amygdaloidal basalt. At the foot of ridges, the landscape is strewn with boulders.
There are local areas of lacustrine sands, including small dunes, along the Lake Superior shoreline to the north. Broad areas of rocky ground moraine are in the west.
LAKES AND STREAMS: Two large lakes: Lake Medora, surrounded by bedrock, and Schlatter Lake on sand lake plain at the southeast edge of the sub-subsection. Rivers: the Gratiot and Montreal.
SOILS: Rocky, red sandy loams and silt loams. Soils are classified as moderately sloping Haplorthods plus Fragiorthods in the south and moderately to steeply sloping Haplorthods plus rock lands in the north (USDA Soil Conservation Service 1967).
PRESETTLEMENT VEGETATION: On bedrock ridges, red pine, white pine, red oak, and paper birch grew on the thin soils (Comer et al. 1993a). Krummholz, resulting from strong winds and heavy snow, was found on most extreme knobs. In protected bedrock valleys and on till, northern hardwood forests were dominated by sugar maple and hemlock. Forests dominated by northern white-cedar, balsam fir, hemlock, and paper birch were located in uplands on thin till and ground moraine west of Ahmeek.
Black spruce, northern white-cedar, and tamarack-dominated swamps occurred along the northern shoreline where soils are poorly drained till over bedrock. Cedar, hemlock, and balsam fir also dominated poorly drained parts of the sand lake plain west of Eagle Harbor, where jack pine grew on excessively drained sand dunes.
NATURAL DISTURBANCE: Windthrows noted in swamps along the northern shoreline.
PRESENT VEGETATION AND LAND USE: European settlements, including Fort William, and several mines and roads had already been established in this sub-subsection by 1845 when the area was surveyed. Major land uses in this sub-subsection have included copper mining, logging, and more recently, recreational/cottage development along the shoreline and inland lakes.
As elsewhere in this subsection, rivers were heavily affected by historical mining and logging activities. The deposition of mine tailings has had a negative impact on coastal wetlands in several places. The large swamp/marsh complex at the north end of Portage Lake was nearly eliminated in the construction of the shipping channel linking that lake to Lake Superior.
RARE PLANT COMMUNITIES: Bedrock balds with krummholz occur on several of the conglomerate or basalt ridges, and bedrock beach occurs along the Lake Superior shoreline. Both of these plant communities have floras rich in boreal and disjunct western montaine species.
RARE PLANTS: Arenaria macrophylla (bigleaf sandwort), Arnica cordifolia (heart-leaved arnica), Carex pallescens (pale sedge), Carex rossii (Ross's sedge), Calypso bulbosa (Calypso or fairy-slipper), Castilleja septentrionalis (pale Indian paintbrush), Ceanothus sanguineus (redstem ceanothus or wild lila), Chamaerhodos erecta var. keweenawensis (Keweenaw rock-rose), Collinsia parviflora (small blue-eyed Mary), Crataegus douglasii (black hawthorn), Dryopteris filix-mas (male fern), Elymus glaucus (blue wild-rye), Epilobium palustre (marsh willow-herb), Pellaea atropurpurea (purple cliff-brake), Phleum alpinum (mountain timothy), Potentilla pensylvanica (prairie cinquefoil), Sagina nodosa (pearlwort), Salix pellita (satiny willow), Scirpus torreji (Torrey's bulrush), Senecio indecorus (rayless mountain ragwort), Trisetum spicatum (downy oat-grass).
RARE ANIMALS: Falco columbarius (merlin).
NATURAL AREAS: The Nature Conservancy Preserves: Horseshoe Harbor; Michigan Nature Association Preserves: Estivant Pines, Keweenaw Shore #1 and #2, Dan's Point, Hylton Memorial, K.W. and T.S. Gunn Memorial, R. and M. Grinnel Memorial, Brockway Mountain, J.H. Klipfel.
PUBLIC LAND MANAGERS: State Forests: Copper Country; State Parks: Fort Wilkins.
CONSERVATION CONCERNS: Mining has heavily degraded the shoreline, as well as creeks and rivers. The full impact upon the biota of mining has not been evaluated.
The area is targeted by some of its major landowners for condominium and second-home development. Bedrock shorelines, and to some extent ridges, are the major focus of this development. To date, no conservation organization is developing a comprehensive plan for protecting this sensitive habitat, even though it is recognized as biologically important and fragile.
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