FOLDING IN MONTANA ROCKIES
FIELD TRIP STOPS – FOLDING INTENSITY AT BEAVER CREEK, MT.
LOCATION: In western Montana, between LaHood Park and Choteau, MT.
GEOLOGIC FEATURES: Progressive folding of Mississippian Limestone
DESCRIPTION: At this outcrop we can see horizontal beds of limestone that rapidly plunge to the vertical and beyond.
(1) What is the Law of Original Horizontality?
(2) When did the Laramide Orogeny take place? What was the direct cause of this tectonic event?
(3) Define: Overturned Fold.
-Devaney, Sarah Anne. “Structural Geology of the Rock Mountain Front.” The Montana Heritage Project. Accessed on 4/19/20: https://serc.carleton.edu/research_education/mt_geoheritage/sites/augusta_choteau/structural_geol.html
-English, Joseph and Stephen Johnston. 2004. “The Laramide Orogeny: What Were the Driving Forces?” International Geology Review, 46(9), pp. 833-838 in Researchgate. Accessed on 4/29/20: https://www.researchgate.net/publication/242170712_The_Laramide_Orogeny_What_Were_the_Driving_Forces
Figure 1 - Photomosaic of the canyon at Beaver Creek, MT. Here we see Mississippian strata folded in various orientations.
Figure 2 - The left side of Figure 1 illustrating horizontal to near-horizontal layering of Mississippian strata.
Figure 3 - Central portion of Figure 1 illustrating the bending of horizontal strata into a vertical or near-vertical
Figure 4 - Right side of Figure 1 illustrating beds dipping to the left that have likely been overturned.
Figure 5 - Photo taken along a view near parallel to the ridge and showing the geological features illustrated in Figures 1 -4.