Hamilton Mound

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

Location Map

geologic sketch map

Parking area is denoted by P. Vehicle access to the quarry is blocked just about everywhere by large boulders. The dashed roads around the east end of the quarry are not recommended because of deep sand in places.

There are two quartzite units: a variegated pink and green unit on the east and a dark gray unit on the west. The contact between the two on the west end of the quarry is a broad shear zone. They are separated on the quarry face by a wide brecciated zone that may be part of the shear zone.

On the west end of the main pit are some nice Pleistocene outcrops.

I have been informed that the mounds have been entirely quarried away.

General Views

Panoramic view from the north showing the east mound (left), the saddle, and the west mound.

View south from the saddle. Keystone Mound, a  small mound surrounded by private land, is on the horizon.
View north from the saddle showing the Lake Wisconsin plain. The access road emerges from the trees just left of center. The parking area, with the author's vehicle, is at the left end of the access road, just above the large sandy area.

East Mound

East end of the pit north of east mound showing altered quartzite with steeply dipping fractures. This may be a continuation of the possible shear zone in the quarry floor to the west.

Shear Zone? in Quarry Floor

These photos were taken about 50 meters north of the quarry face at the east end of the west mound. A rapid succession of different-colored units, all highly fractured, suggests a shear zone.

The Brecciated Zone

Closeups of the brecciated rocks and a distant view of the brecciated zone. It is curious that almost all the Proterozoic quartzites in Wisconsin display this sort of brecciation.

Views of West Mound

Variegated quartzite


Dark Gray Quartzite

The left view shows the contact between the quartzite (lower right) and the brecciated zone (upper left). In both views there is a large round mass of quartzite just below the center that may be a large tectonic boudin.


West End Shear Zone


Panorama of West Mound

Upper view is a panorama with variegated quartzite in the distance, the brecciated zone occupying the center of the view, and the dark gray quartzite on the right. The lower view has contacts superimposed.


Although the main interest in the quarry is the Precambrian quartzite, there are some nice Pleistocene outcrops visible in the far west end of the pit. There are rhythmically bedded silty outwash deposits (left) overlain by gravelly and sandy outwash (right).


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Created 20 September 2000, Last Update 20 September 2000