| Abstract: | Dating of orogenic rock units in the central part of the Madison Range shows that Laramide deformation was virtually completed by the end of the Cretaceous. Early Campanian K-Ar dates of about 79 m.y. were obtained from welded tuffs in the basal part of the Livingston Formation, a volcanic and volcaniclastic assemblage that is conformable with underlying Cretaceous clastic rocks and with the overlying Sphinx Conglomerate. The Sphinx and the Livingston were deformed by the Hilgard fault system which extends along the western side of the southern two-thirds of the range. This north-trending fault system represents the culmination of Laramide shortening within the range. Dating of hornblende indicates an approximate date of 68-69 m.y. B.P. for emplacement of the igneous suite. The dacite postdates movement along faults of the Hilgard fault system, and postdates the synorogenic Sphinx Conglomerate. -from Authors |
| Genre: | Article |
| ProdID: | 70014559 |
| Citation Author: | Tysdal, R. G.; Marvin, R. F.; Dewitt, E. |
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| Citation End Page: | 868 |
| Citation Issue: | 7 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geological Society of America Bulletin |
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| Citation Number Of Pages: | 10 |
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| Citation Search Results Text: | Late Cretaceous stratigraphy, deformation and intrusion in the Madison Range of southwestern Montana ( USA).; 1986; Article; Journal; Geological Society of America Bulletin; Tysdal, R. G.; Marvin, R. F.; Dewitt, E. |
| Citation Start Page: | 859 |
| Citation Volume: | 97 |
| Citation Year: | 1986 |
| Type: | citation/reference |
| Text: | Late Cretaceous stratigraphy, deformation and intrusion in the Madison Range of southwestern Montana ( USA).; 1986; Article; Journal; Geological Society of America Bulletin; Tysdal, R. G.; Marvin, R. F.; Dewitt, E. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1986 00:00 -0600 |
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