Schoonmaker Reef
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Schoonmaker Reef
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| Location | Wauwatosa, Wisconsin |
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| Coordinates | 43°2′50″N 87°59′37″W / 43.04722°N 87.99361°WCoordinates: 43°2′50″N 87°59′37″W / 43.04722°N 87.99361°W |
| NRHP Reference # | 97001266 |
| Significant dates | |
| Added to NRHP | September 25, 1997 |
| Designated NHL | September 25, 1997 |
Schoonmaker Reef, also known as Wauwatosa Reef, Schoonmaker Quarry, Raphu Station or Francey Reef is a 425 million year-old fossilized reef in Wauwatosa, Wisconsin. It was discovered in 1844 by Increase A. Lapham and Fisk Day on the site of a quarry owned by the Schoonmaker Family. Geologist James Hall declared its significance in 1862. It was the first ancient reef described in North America, and among the first described in the world. It is located North of W. State St., between N. 66th St. and N. 64th St. extended, in Wauwatosa. It was declared a National Historic Landmark in 1997.
The Schoonmaker Reef formed approximately 425 million years ago during the Silurian period. It is largely dolomite, a sedimentary rock of calcium magnesium carbonate (CaMg(CO3)2) that is similar to limestone. The reef is stratigraphically consistent with the Racine Dolomite, a formation in Wisconsin and Illinois. The exposed portion of the reef is in the Menomonee River valley in Wauwatosa, Wisconsin. It exists as a massive, rock hill that stretches in a 600-foot (180 m) outcrop. It is exposed on the lower 20 feet (6.1 m) of a 60-foot (18 m) bluff; the upper portion of the bluff is formed by glacial sediments left in the last million years. The reef contains a variety of fossils from Silurian-era organisms, including trilobites.
The first known human interaction with the reef was in 1838, when Joseph Higgins identified it as a source of lime. Lime burning at the reef may have first occurred five years earlier. Silas Brown constructed lime kilns in the 1840s which remained in use until 1857. Increase A. Lapham first identified the reef as an area of geological interest in 1844.
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