Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
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McCaslin Mountain is an elongated quartzite monadnock that forms the northern limb of the McCaslin Syncline. Thunder Mountain (TM) is another quartzite monadnock that defines the eastern nose of the syncline, and the Baldwin Conglomerate (BC) is a thin lens of quartzite and metaconglomerate that may represent equivalent rocks on the southern limb.
On the map above, quartzite is yellow. Precambrian X metavolcanic rocks (Xmv) are green and Precambrian Y granitic rocks (Xmv) are dark pink. Precambrian Y granitic rocks of the Wolf River Batholith (Yg) are light pink and "rhyolite" (Rh) is lavender. The rhyolite is a quartz porphyry that probably is a high-level intrusive rock of the Wolf River Batholith. Contour lines are at 50 meter intervals with maximum elevations of 500 meters.
The map above shows the eastern end of McCaslin Mountain. The heavy contour is 400 meters and other contours are at 10-meter intervals. Note that there are several deep gorges through the ridge. They are obviously a pre-Pleistocene superposed drainage but their age and significance are unknown.
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A short road, Conklin Road, leads west from County C to the top of
the easternmost knob of McCaslin Mountain. A short side road leads to
communication towers at the summit (Locality A on the map above).
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Like much of the Precambrian of Wisconsin, the extent of the
McCaslin quartzite can be mapped from drift and topography, but
structure is hard to determine because of scarce outcrop and lack of
structural predictors. A nice outcrop occurs in the woods east of the
summit tower. Below: like most of the quartzites, the rock is very uniform but does show hints of steeply south dipping bedding. |
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The surrounding township is called Silver Cliff because of a small silver prospect once worked in the quartzite. Feldspathic mineralization occurs widely in this end of McCaslin Mountain. |
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A large rocky knob about 100 meters south of the intersection of County F and County C (Locality B on the map) is fine-grained sugary pink quartzite. below is a large tree straddling an outcrop. |
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Harvey Lane is a short unpaved road that leads to the base of McCaslin Mountain (Locality C on the map above). Bear right at each unmarked fork. From the end of the road a steep climb of about 100 meters ascent leads to outcrops. |
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Left: extensively quartz-veined quartzite. |
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Left: large bounder on the ridge. |
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Left: the boulder is brecciated, as are most of the quartzites in
Wisconsin. Below: looking east across the valley to the eastern knob (Locality A). |
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Left: around the mountain are thick moraines. At left is a small kettle. |
The central part of McCaslin Mountain is shown above. McCaslin Tower Road (M) crosses the ridge. It gets its name from a long-defunct fire lookout tower. There is abundant float along the road but no outcrop. Knowles Creek Road (K) also crosses the ridge
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A small pullout on Highway 32 leads to National Forest trails on both sides of the highway. Locality X east of the highway at one time offered a lookout but is now overgrown. |
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A couple of hundred meters east of the highway, a large knob crops out. |
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Left: As usual there is brecciation in the quartzite. |
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Left and below: the quartz vein filling in the breccia created crystal pockets, which were once exploited rather brutally (including blasting) by collectors. Collection is now prohibited, though exhaustion of the crystals probably played a larger role in ending the practice. |
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| Below: conglomeratic facies. | |
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Created 16 April 2007, Last Update 23 April 2007
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