Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
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The map above shows the principal Precambrian outcrops in south-central Wisconsin, the so-called "Baraboo Interval" (1700 Ma) granite-rhyolite terrane. Towns without outcrops are yellow, rhyolite localities are purple, granite localities are green. The Glovers Bluff impact structure is also in the map area and is light blue.
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Three large quarries are adjacent to the cemetery east of town. The northernmost and southernmost are closed to visitors. |
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The southern quarry is now a pond for a private residence but it was open in the 1980's when the pictures below were taken. These views are looking southwest from the edge of the cemetery. |
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Left and below: the quarry seen from the same vantage point in 2006. |
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View from the south. A thick lens of Cambrian basal conglomerate lies atop the rhyolite. The houseboat in the picture above is visible at left. |
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Left: closer view of the basal conglomerate Below left: a mass of brown conglomerate fills a crevice higher up the quarry wall. Below right: east wall of the quarry. |
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The crevice fill is visible at far right in this picture from the 1980's Below are closer views of the conglomerate. |
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Left: fresh rhyolite appears uniform and featureless, but where weathered (below) flow banding is visible. |
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Overlooking Berlin from the east end of the quarry. |
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General views of the quarry from the east. |
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Left and bottom left: a thick mass of Cambrian basal conglomerate overlies the rhyolite on the north side of the quarry. |
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The Precambrian-Cambrian contact in Wisconsin is usually marked by basal conglomerate, and the Berlin Quarry is no exception.
| Distant views of the basal conglomerate from the west end of the quarry | |
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| Detailed views of the basal conglomerate from the west end of the quarry | |
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Left and below: the unconformity |
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Above: close-up of the conglomerate. |
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Below: Arlyn's hand spans about a quarter of the earth's history, from 1.7 billion year old metarhyolite to Cambrian basal conglomerate. |
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On unaltered surfaces the rhyolite appears mostly featureless. |
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Remnant of an old drill hole. |
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Closeup of the rhyolite. Note the porphyritic texture and flow banding on the surface below the drill hole. |
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Left and below: closeups of the rhyolite showing porphyritic texture accentuated by weathering. |
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Left and below: where weathered, the rhyolite shows evidence of flow banding. |
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Glacial striations |
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Left and below: Striations, chatter marks, and small crescentic gouges. |
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Created 19 May 1999, Last Update 19 May 1999
Not an official UW Green Bay site