Red Hill Syenite
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The Red Hill Syenite ("Red Hill Syenitic Complex",[1] "Red Hill Alkaline Igneous Complex",[1] "Red Hill Intrusion",[2] or "Red Hill Layered syenitic complex"[3]) is a layered igneous rock complex in central New Hampshire, about 20 mi (32 km) east of Plymouth. The Red Hill Syenite is part of the White Mountain magma series, which underlays the White Mountains of New Hampshire. Red Hill is roughly oval-shaped, covers just under 7.7 square miles (20 km2), and has a summit elevation of 2,028 feet (618 m).[2]
Red Hill Syenite | |
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Stratigraphic range: Early Jurassic, ~199–197 Ma | |
Lithology | |
Primary | Syenite |
Other | feldspathoid, granite, feldspar |
Location | |
Region | White Mountains of New Hampshire |
Country | United States |
The complex is made of six distinct units, the order of intrusion of which was determined by cross-cutting relationships. The units are, in order from oldest to youngest, the Outer Coarse Syenite, the Nepheline Sodalite Syenite, the Fire Tower Syenite, the Garland Peak Syenite, the Watson Ledge Quartz Syenite, and the Interior Fine Granite. The rock complex is between 197-199 million years old, dated to the Early Jurassic epoch, making it one of the oldest sections of the White Mountain magma series.[2] The Interior Fine Granite unit is the youngest, and formed about 10 million years after the rest of the complex.[1]