Soils and Geology of Wisconsin Field Trip, May 2006

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Highway 29 Near Shawano

Road cuts on Highway 29 south of Shawano expose the contact between the Cambrian sandstones and Prairie du Chien dolomites.

Tigerton Dells

Coarse granite of the Wolf River Batholith. The secret to finding huge feldspar crystals is using the right size hammer. But even with a regular hammer these are pretty impressive.
Professor Luczaj points out the location.
View looking upstream

Nine-Mile Granite

Quarries south of Rib Mountain are the source of so-called "rotten granite" used in lanDscaping. The grainte is mechanically weathered but not very chemically altered.
Large xenolith in the granite.

Large rounded granite boulders are not the result of water or glacial action but are the residual cores of former joint blocks.

Rib Mountain

The quartzite monadnock at Rib Mountain was once believed to be the highest point in Wisconsin.
How the quartzite became spheroidal in places is a bit of a mystery.

Below: ripple marks in the quartzite.
View from Rib Mountain
Night view from Rib Mountain

Brokaw

Highway cuts at Brokaw expose well displayed sedimentary structures in the metasedimentary rocks.
Metaconglomerate layers.
General view of the outcrop.
A rare set of nearly complete crossbeds, showing topset, foreset and bottomset layers.
More cross beds.
A coarse metaconglomerate layer, with finely laminated sediments above and cross beds below.

Irma Hill

Irma Hill is an inlier of Cambrian sandstone far removed from any other Paleozoic outcrops.
General view of the outcrops.
Closeup of the sandstone.
Ripple marks in the sandstone.

Harrison Hills

Trillions of trilliums.
"I been lost before an' dis is what it looked like." - Da Yoopers.

Our attempt to get up on top of one of the ice-walled lake plains didn't work out.
Unlike geologists, soil scientists never have to worry about exposure. Kevin Fermanich dug a soil pit and laid out a profile of the local spodosol.

Floating Bog

The Army says "If it's not raining, it's not training." So what better time to visit a floating bog than in the rain?
The bog consists of a thick vegetation mat with water beneath. A soil auger meets resistance for a bit and then pushes effortlessly.
There's also a lot of water on top of the vegetation mat.

Powell Kyanite Schist

There aren't many good exposures of high grade metamorphic rocks in Wisconsin. This exposure near Powell consists of kyanite schist.
The outcrop lies in an otherwise completely featureless expanse of forest.
Simone Kolb expostulates on the meaning of the schist.

Archean Gneiss Near Hurley

Excellent exposures of Archean gneiss occur just south of Hurley. We're on the edge of the Superior craton here, north of the Niagara Fault, which is hidden under glacial deposits.
Banding in the gneiss.
Glacial polish and striations on top of the outcrops.

Tyler Formation, Hurley

Thick accumulations of slate and metagraywacke represent the former continental slope of the Superior craton.
A good illustration of the difference between bedding and foliation.
A quick grocery stop allows for a Frisbee tournament.
Professor Fermanich displays fine Frisbee-chasing form

Pillow Basalt Near Wakefield

Archean pillow basalts
Spectacular glacial striations atop the outcrop.
The smooth polished steep surface could be slickensides due to faulting, but the texture seems to merge seamlessly into the glacial polish on top.

There are a lot of perplexing outcrops like this one. Why would glacial ice flow down a steep outcrop and make striations? Or was it ice? Could it have been subglacial melt water, or wind?
Here we have a sharp corner between two polished and striated surfaces. Glacial ice seems very unlikely to have done this.
Volcanic breccia.
Pillows can often be recognized by their concentric structure and vesicles.
Left, a concentrically zoned pillow.

Below, a very large pillow.
Left, pillows accentuated by weathering.

Below: the light just grazes the outcrop surface to bring out the pillow structure.

Lake Gogebic

Keeweenawan Volcanic Rocks at Bergland

Lake Superior

An impromptu stop just before going up to Lake of the Clouds. Lake of the Clouds is beyond the peak on the skyline.
Red lake sediments have essentially the same origin as red tills in northeastern Wisconsin - red clays derived from Lake Superior.
What unknown ancient civilization created these mysterious stone structures?
Left: Current ripples

Below: heavy minerals weathered out of the till and the Keeweenawan rocks spectacularly outlined seimentary structures .

Lake of the Clouds

Van Riper State Park

Above: setting up camp intently.

Below: sunset views.

Campeau Gneiss, Marquette

Presque Isle Park, Marquette

Jacobsville Sandstone overlying Archean rocks.
Visiting this locality can be a real cliffhanger.
Jointed sandstone underwater in Lake Superior.
On the north end of Presque Isle Park is a puzzling Archean peridotite.
The peridotite is extensively altered and veined with carbonates.
Looking west across the bay.
Ore dock at the entrance to Presque Isle Park.

Marquette Synclinorium

Left and below: spectacular stromatolites in the Kona Dolomite.

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Created 08 September 2006, Last Update 15 January 2020