The Baraboo Range is a mountain range in Columbia County and

Sauk County Sauk County is a county (United States), county in Wisconsin. It is named after a large village of the Sauk people. As of the 2020 United States census, 2020 census, the population was 65,763. Its county seat and largest city is Baraboo, Wiscon ...

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

. Geologically, it is a

syncline In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed ...

fold consisting of highly eroded

Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

. It is about long and varies from 5 to in width. The

Wisconsin River The Wisconsin River is the longest river in the U.S. state of Wisconsin, at approximately 430 miles (692 km) long. As a tributary of the Mississippi River, it is part of the Mississippi River System. The river's name was first recorded in 1673 b ...

, previously traveling in a north to south direction, turns to the east just north of the range before making its turn to the west towards the

Upper Mississippi River The Upper Mississippi River is the portion of the Mississippi River upstream of St. Louis, Missouri, United States, a city at the confluence of its main tributary, the Missouri River. Historically, it may refer to the area above the Arkansa ...

. The eastern end of the range was glaciated during the Wisconsinian glaciation, while the western half was not, and consequently, marks the eastern boundary of Wisconsin's

Driftless Area The Driftless Area, also known as Bluff Country and the Paleozoic Plateau, is a topographic and cultural region in the Midwestern United States that comprises southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and the extreme ...

. The city of Baraboo is in the center of the valley. The range was designated a

National Natural Landmark The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best e ...

in 1980.

Geology

These hills were formed from deposited sediment in a shallow sea 1.7 billion years ago. This sediment was metamorphized into quartzite, deformed, then uplifted. These outcrops may have been islands when the region was covered by shallow seas in the Cambrian.Hanson, G. F.
''Geology of the Baraboo District, Wisconsin''
, The University of Wisconsin Extension, November 1970, Information Circular 14 The Baraboo River divides the range in half, flowing through Upper Narrows Gorge near Rock Springs and travels onto its confluence with the

downstream from

Portage Portage or portaging ( CA: ; ) is the practice of carrying water craft or cargo over land, either around an obstacle in a river, or between two bodies of water. A path where items are regularly carried between bodies of water is also called a '' ...

through the Lower Narrows. The Baraboos are composed of resistant

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

) which has formed an erosional remnant or

Monadnock An inselberg or monadnock ( ) is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa, a similar formation of granite is known as a koppie, an ...

, resulting in

topographic prominence In topography, prominence or relative height (also referred to as autonomous height, and shoulder drop in US English, and drop in British English) measures the height of a mountain or hill's summit relative to the lowest contour line encircling ...

. The mountains may have formed as long ago as the late Precambrian. These formations were buried by

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

and are still being uncovered by the erosion of the softer, overlying rocks. Devil's Lake, the centerpiece of Devil's Lake State Park, was formed from

terminal moraine A terminal moraine, also called an end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front e ...

s blocking access to its outlet, creating what is today an

endorheic lake An endorheic lake (also called a sink lake or terminal lake) is a collection of water within an endorheic basin, or sink, with no evident outlet. Endorheic lakes are generally Saline water, saline as a result of being unable to get rid of solutes ...

(i.e., a lake lacking a surface outlet to the world's oceans). In addition to Devil's Lake State Park, significant sections of exposed quartzite can be found at Ableman's Gorge State Natural Area and Lower Narrows State Natural Area. Ableman's Gorge is a natural gorge featuring unconformable contacts between the quartzite and younger Cambrian

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, exposed through a combination of erosion and modern quarrying. Bluffs at Lower Narrows carved by the Baraboo River expose contacts between the quartzite and younger volcanic

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

References

* Steven Dutch
Devil's Lake
Retrieved July 27, 2007 (With map)

Retrieved July 27, 2007
Baraboo Range Protection Plan
Sauk County, Retrieved July 27, 2007

Wisconsin Department of Natural Resources, Retrieved July 27, 2007 * Keith Montgomery
The Baraboo Ranges and Devil's Lake Gorge: A Geologic Tour
Retrieved April 30, 2019

External links

* {{authority control Driftless Area Landforms of Columbia County, Wisconsin Landforms of Sauk County, Wisconsin Geology of Wisconsin Inselbergs of North America Mountain ranges of Wisconsin National Natural Landmarks in Wisconsin