Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
The fall foliage was near its peak on Highway 29. | |
Beautiful fall view of Rib Mountain. | |
The pre-Pleistocene bedrock valley of the Wisconsin River. |
This trip had one of the longest legs ever before the first stop. All the stops were within a few miles of Mellen. This outcrop is a few miles south on State Highway 13, tastefully decorated by primitive artists. | |
A couple of miles east of Mellen off a side road are outcrops of the Archean Ramsay Formation and Proterozoic Palms Quartzite. | |
Close up of the Ramsay Formation, an amphibolite. | |
Looking at the Palms Quartzite. The outcrops of Ramsay Formation are near the vehicles. The contact is concealed. | |
Left and below: some of the thicker beds have spectacular plumose fracturing. Note how it splays into en echelon fractures near the contacts. | |
Plumose fracturing originated at one point in this bed and radiated in all directions. | |
Higher up (to the north) the rocks grade into iron formation. | |
Left: nice en echelon quartz-filled cracks. Below: Yup, it's magnetic! |
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Red jasper in the iron formation. |
A large outcrop of Mellen Gabbro is just north of town, within sight. | |
Left: small basalt dike Below: the gabbro is essentially anorthosite with long plagioclase laths. |
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Near the Mellen Gabbro is another intrusive unit, the Mellen Granite, which fed rhyolite flows in the Keeweenawan rift. | |
Not far north of the gabbro outcrop is a spectacular outcrop of intrusive breccia, with gtabbro clasts enclosed by granite. | |
Left: unusually shaped inclusion next to crystal-lined cavity Below: Crystal-lined cavities are common, especially in areas with pegmatitic texture, indicating that the intrusion was very shallow, since open cavities cannot form under high pressures. |
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Left: some gabbro inclusions appear to exhibit layering. | |
There are some areas of coarse pegmatite with graphic texture. | |
Below: views of the Bad River. | |
Above: Copper Falls itself is not very dramatic. | Below: Brownstone Falls is bigger and higher than Copper Falls. |
Vertical layers of Copper Harbor Conglomerate. | |
Keeweenawan sedimentary rocks | |
Staircase down to the river | |
Keeweenawan sedimentary rocks. | |
The prominent vertical rib on the right is Copper Harbor Conglomerate. The recess to its left is Nonesuch Shale, and the massive unit on the left is Freda Sandstone. | |
Bridge over the Bad River | |
Climbing up to the top of the gorge | |
Freda Sandstone | |
Copper Harbor Conglomerate | |
Brownstone Falls is on the right. | |
Brownstone Falls. The rocks are lighter and pink because they're rhyolite, probably erupted from the Mellen Granite magma chamber. | |
Oh, deer! | |
Inclusions in flagstones of Tyler Formation. |
Professor Luczaj ferreted out a ski lodge near Ironwood. Wise move, as will shortly become apparent. | |
A roof looks good tonight. |
Not tenting was definitely a good plan. | |
Breakfast | |
We are going to charge an Adventure Camping surcharge plus a triple Character Building surcharge for this. | |
The Tyler Formation is a thick sequence of greywackes and slates, a former continental slope deposit on the Superior Craton. Below: the snow made for pretty scenery but poor rock visibility. |
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Graded bedding in a greywacke bed. Below: trying to see the rocks |
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Slickenside steps on a fracture surface. | |
Snowbow! There was enough light rain mixed with the snow to give us this unusual sight. | |
Cleavage is obvious in the slates but absent in the greywackes. | |
Snow on the trees was lovely. | |
Snow on the outcrops, not so much. Under good conditions this outcrop has spectacular pillows but this one was the only one visible. | |
Headed east to Bergland. |
Near Lake Gogebic there had been hardly any snow. | |
This stop features a variety of lithologies, including this arkose. | |
Cross bedding in the arkose. Below: there was little snow at road level but some on the hilltops. |
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Lithic sandstone resting atop a basalt flow. Professor Ryan Currier (right) ponders the outcrop. | |
Above: columnar jointing in rhyolite. | Below: A layer of lithic sandstone between rhyolite flows. |
A porphyritic rhyolite outcrop a couple of miles north of Bergland had closely spaced lamellar joints. | |
Headed north |
Fall foliage. | |
If you can't get the concept of strike and dip here, maybe you should re-think your major! The formation is Freda Sandstone. The southeast dip is anomalous since most Keeweenawan rocks in the region dip northwest. | |
Below: These may be algal mat structures. | |
Parting lineation on bedding surfaces indicates wave direction. | |
there are numerous small but nice potholes here. | |
Views on the way to Lake of the Clouds | |
Views from the overlook, beginning in the north and moving around to west. | |
Epidote filled vesicles in a basalt flow. | |
Glacial polish and striations. Below: the group gathers for a picture. |
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View north to Lake Superior. | |
The circular patches of vesicles may be inclusions of vesicular basalt or pipes where gases escaped. | |
Union Bay features Lake Superior surf plus an astounding array of sedimentary structures. Below: Mud cracks |
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The pretty day at Lake of the Clouds was a very fortunate brief window. | |
Conglomerate layer in the sandstone. | |
Mud cracks on two scales. | |
A beach not far from Union Bay Campground is a good place to observe dynamic beach processes. | |
Wave action was creating a lag deposit of pebbles in the surf zone. It's also obvious how parting lineation forms. | |
Red Pleistocene glacial lake clay. | |
Wave action leaves streaks of heavy minerals | |
A magnet confirms they're magnetite. |
A steep trail leads up Tower Hill on the outskirts of town. Below: The Palms Quartzite is an attractive thin-bedded unit. |
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Above: views of Wakefield. | Below: the Palms grades into a darker facies to the north but there is no iron formation. It may be exposed further down the north slope of the hill. |
After the beautiful weather at Lake of the Clouds, it looked like a fine day from then on. But it was not to be. Here a snow squall blows in. |
At the mouth of the Presque Isle River are some wonderful potholes. | |
A suspension bridge crosses the river. | |
Looking north to Lake Superior. Note the joint control on the channel. | |
The potholes here are among the most crisp and perfectly round anywhere. | |
Looking downstream toward lake Superior. | |
Looking upstream. | |
Ball and pillow structures, load structures formed when coarse sediment is suddenly dumped on still wet sediments below. | |
The valley beyond the hill is a high water mouth of the river. | |
Views of the Presque Isle River | |
Climbing out of the gorge |
Left and Below: At high water this falls stretches across the gorge but at low water the falls is pretty modest. | |
Above, a small fall upstream Below: potholes |
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Two potholes straddling a fracture. Obviously the potholes were initiated when rock spalled aoff along the fracture. | |
Left and below: cross-bedding. | |
Sunday morning, there was still snow on the ground. | |
Mmmm, that feels goood! |
The welcome center on US 51 in Hurley has several gigantic cores, which may have been drilled for starting a shaft, drainage, ventilation, or emergency access. | |
This could be Mellen intrusive breccia. The Wikipedia article on Core drills links to an article in the December, 1943 issue of Popular Science that describes a new drilling technique and says: "today, 1000 feet below the earth's surface at Hurley, Wis., it is cutting a mine shaft down toward the 3000 foot level of an operating iron mine." In all likelihood, this is a piece of that core. That method could cut cores up to 16 feet long but is no longer used because it has been superseded by faster drilling methods. |
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Historical placard on Iron Mining. |
One of the few good outcrops of high grade metamorphic rocks in Wisconsin. The significance of the cairns is unknown. | |
The hills on the horizon are the Harrison Hills, a collection of kames and ice-walled lake plains. | |
The Harrison Hills are a maze of kames and kettles. | |
Even though soil scientists go around uttering blasphemies like "soil outcrop," this is a Soils and Geology field trip, meaning we gotta have a soils stop. | |
Professor Luczaj fills in for Professor Fermaich, who didn't come along this time. | |
Anyone who had spodosol, come up and collect your prize. It's weakly developed but has the bright orange B horizon and somewhat bleached A horizon. If that seems at odds with the deciduous forest, bear in mind this is all second or third growth and the original forest was pine. | |
Left and below: atop one of the ice-walled lake plains. A small plateau of glacial and lake sediments. | |
Professor Luczaj explains how an ice-walled lake plain forms. The drawing is now on sale at Sotheby's. | |
Above: looking toward the eastern end of the plain. | Below: to the west, the topography drops off steeply. |
The Harrison Hills are on the skyline. |
Irma Hill is capped with indurated sandstone which scanty fossils indicate is Cambrian. This view looks west over the Wisconsin River valley. | |
One of the most interesting features here is an erratic of schist with big staurolite crystals. | |
Staurolite crystals stand out in relief on the boulder. | |
Left and below: autumn foliage from Irma Hill. | |
The big staurolite boulder is behind the yellow bushes just right of the small pine. | |
Outcrops on Irma Hill. | |
The outcrop with orange leaves next to it has ripple marks. |
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Created 11 October 2012, Last Update 24 May 2020