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Geologic units in Douglas county, Wisconsin

Additional scientific data in this geographic area

Chengwatana Volcanic Group (Middle Proterozoic) at surface, covers 45 % of this area

Gray basalt flows, interflow breccia, tuff, and minor sedimentary rocks

Copper Harbor Conglomerate (Middle Proterozoic) at surface, covers 26 % of this area

Red lithic conglomerate and sandstone; mafic to felsic volcanic flows similar to those of the unnamed formation (unit Yu) are interlayered with the sedimentary rocks.

Bayfield Group; Orienta Sandstone (Middle Proterozoic) at surface, covers 19 % of this area

Poorly sorted arkosic sandstone

Oronto Group; Freda Sandstone (Middle Proterozoic) at surface, covers 4 % of this area

Mainly reddish-brown, medium- to fine-grained lithic arkosic sandstone, siltstone, and micaceous silty shale.

Bayfield Group; Devil's Island Sandstone (Middle Proterozoic) at surface, covers 4 % of this area

Well-sorted quartzose sandstone

Granophyre (Middle Proterozoic) at surface, covers 0.8 % of this area

Granophyre

Gabbroic rocks of Keweenawan affinity (Middle Proterozoic) at surface, covers 0.6 % of this area

gabbro, anorthosite, granite, peridotite

Oronto Group; Nonesuch Shale (Middle Proterozoic) at surface, covers 0.4 % of this area

Gray, green, and brown lithic siltstone, shale, and sandstone. Copper sulfides and native copper occur locally near base

Bayfield Group; Chequamegon Sandstone (Middle Proterozoic) at surface, covers < 0.1 % of this area

Poorly sorted arkosic sandstone

Sandstone, siltstone, and local conglomerate (Mesoproterozoic) at surface, covers < 0.1 % of this area

Sandstone, siltstone, and local conglomerate. Includes the Hinckley Sandstone and Fond du Lac (youngest detrital zircons ~1,000 Ma) and Solar Church Formations; deposition in eolian, fluvial, and lacustrine environments.

Ferromonzodiorite forming the upper contact zone (Mesoproterozoic) at surface, covers < 0.1 % of this area

Ferromonzodiorite forming the upper contact zone.

Gabbro (Mesoproterozoic) at surface, covers < 0.1 % of this area

Gabbro. Includes the Western Margin, Greenwood Lake, Bald Eagle (~1,098), Lake One, Lake Three, Wilder Lake, and Osier Lake intrusions.