.TOURING
COLORADO GEOLOGY
Paleozoic
Rocks in Chaffee County|
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.TOURING COLORADO GEOLOGY |
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Paleozoic
Rocks in Chaffee County |
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Driving south on 285 just a few miles into Chaffee County, you pass from a small broad valley into a fairly tight, restricted canyon on your way down into Buena Vista. | The rocks at this narrowing of the valley are lower Paleozoic and express three formations before Pre-Cambrian rocks are encountered further south. |
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Composite of the outcrop on west side of 285. |
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These formations are all Ordovician in age. The Manitou rests on pre-Cambrian granite, the contact being unconformable and to the left of this outcrop. | The overlying Chaffee (Devonian) and Leadville (Mississippian) formations are not well exposed here. |
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Fremont |
Dolomite to dolomitic limestone, gray crystal size 1/8 to 1 mm, massive, fossiliferous, corals common. |
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Harding |
Quartzite and sandstone, white to gray and green, very fine-grained. Thin gray and greenish gray shale and siltstone partings. Contains worm borings and fucoids. |
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Manitou |
Dolomite to dolomitic limestone, light to dark gray, crystals 1/8 to 3/4 mm, thin-bedded in lower part, becoming more massive at top. Seams and concretions of white to cream chert common in lower third of section. Fossils very scarce. |
| Descriptions above from: Hutchinson, R. M. et al., 1960, Geology of West-Central Colorado, Second Day, Table 1. Stratigraphic Section at Trout Creek, p. 147. |
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PreCambrian/Manitou contact |
The contact of the Manitou (Lower Ordovician) and pre-Cambrian granites can be seen along 285 just south of the above outcrop. All the Cambrian rocks have been eroded away. |
Detail of Pre-Cambrian granite |
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May 22, 2001 |
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