Carlin Canyon, Nevada

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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The Carlin Canyon unconformity is a classic geologic locality where two orogenic events are preserved. Middle Paleozoic (Mississippian) layers were tilted, eroded, then overlain by late Paleozoic (Pennsylvanian) layers. Then the rocks were tilted again. The Mississippian layers are now vertical and the mid-paleozoic unconformity is now steeply tilted.

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Carlin Canyon, NevadaEast of the Carlin tunnels on I-80 are thick horizontal Tertiary continental deposits.
Carlin Canyon, NevadaThe unconformity is easy to see north of I-80 just west of the tunnels near Carlin. The truncation of the vertical layers marks the unconformity.
Carlin Canyon, NevadaThere's a pulloff immediately west of the tunnels but re-entering the highway is dangerous because traffic in the tunnels is invisible. Sound rather than sight is the best indicator.
Carlin Canyon, NevadaExit at the first Carlin exit and head south until the street ends. There is a sign for the canyon.
Carlin Canyon, NevadaView of the highway and railroad tunnels
Carlin Canyon, NevadaThe road follows old US 50 under the interstate 
Carlin Canyon, NevadaThe truncation of the vertical layers marks the unconformity.
Carlin Canyon, NevadaThe BLM has recognized the geologic significance of the site.
Carlin Canyon, Nevada Carlin Canyon, Nevada
Carlin Canyon, NevadaView of I-80 and the tunnels.
Carlin Canyon, NevadaLeft and below: vertical Mississippian conglomerate layers of the Tonka Formation. Near the unconformity they include siltstones and cherts. The Pennsylvanian Strathearn Limestone makes up the gently dipping layers above the unconformity.
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Carlin Canyon, NevadaLeft and below: close-ups of the unconformity. Mississippian conglomerates are vertical and orange, late Paleozoic limestones are gray and dipping to the right.
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Carlin Canyon, NevadaLate Paleozoic limestones
Carlin Canyon, NevadaClose-up of late Paleozoic limestones
Carlin Canyon, NevadaCliff of late Paleozoic limestones
Carlin Canyon, NevadaAlthough little more than a stream, the Humboldt River snakes around and through the ranges of Nevada and furnishes a travel route followed by everyone from Indians to the modern Interstate.
Carlin Canyon, NevadaA placard on the far end of the road just before it ends describes the history of the route.
Carlin Canyon, NevadaView north along the Humboldt River to the unconformity. The hill left of the river is a dip slope in the limestone.
Carlin Canyon, NevadaCloser view of the unconformity, here visible mostly by color contrast.
Carlin Canyon, NevadaLeft and below: views south along the Humboldt River looking back toward the historical marker. The dip slope is on the right side of the river.
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Carlin Canyon, NevadaView west from the unconformity of the vertical conglomerate layers.
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Carlin Canyon, NevadaThe unconformity actually can be traced for some distance. Here we see a ridge of vertical conglomerate in the foreground and dipping limestone layers on the top of the distant ridge. This view is looking east from near the geologic marker.
Carlin Canyon, NevadaThe Interstate tunnels actually cut through the unconformity. The red band right of the tunnels marks the start of the vertical conglomerates, and most of the face consists of limestone. Because we are looking perpendicular to the strike, the angular relationships are not obvious.

There is actually a double unconformity here. At far left horizontal fan deposits can be seen resting on the limestones.

Carlin Canyon, NevadaFan deposits (left of the yellow sign), limestone (yellowish blocky material) and conglomerates (reddish). The conglomerate band can also be traced horizontally across the hill to the right of the cut. The top is the unconformity.

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Created 7 April 2003, Last Update 01 July 2012

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