Uplift associated with the Rocky Mountains occurred earlier in the east and proceeded westward, a pattern that is consistent with a number of theories regarding the uplift of the Rocky Mountains. The widespread unconformity during the early Paleocene in western Colorado indicates that the area was uplifted initially with deposition proceeding later than the Front Range of the Rocky Mountains.
 |
| Basin |
Oldest Age Estimate |
Youngest Age Estimate |
Method |
Period |
Author |
| Crazy Mountain Field |
55.5 MYA |
40.5 MYA |
Relative Dating |
Early Eocene |
Thom, 1957 |
| Powder River Basin |
62 MYA |
60 MYA |
U-Th/He Apatite Dating/Biostratigraphy |
Middle Paleocene |
Weaver & Flores, 1988; Crowley et al. 2002 |
| Big Horn Basin |
65 MYA |
62 MYA |
U-Th/He Apatite Dating/Biostratigraphy |
Early Paleocene |
Weaver & Flores, 1988; Belt et al. 1997; Crowley et al. 2002 |
| Wind River Basin |
54 MYA |
53 MYA |
Biostratigraphy |
Wa-3 Biozone NALMA |
Winterfeld & Conard, 1983 |
| Hanna and other Basins |
62 MYA |
62 MYA |
Biostratigraphy |
Torrejonian/Tiffanian NALMA |
Lillegraven et al. 2002 |
| Green River Basin |
53 MYA |
30 MYA |
Old date: Sr/Sr Ratio/Biostratigraphy
Young date: K/Ar radiometric dating |
Middle to Late Eocene |
Swanson, 2003; Balls et al. 2004 |
| Washakie/Sand Wash Basins |
57 MYA |
55.5 MYA |
Biostratigraphy |
Tiffanian to Wasatchian NALMA |
Honey & Hettinger, 1989 |
| Middle/North Park |
66 MYA |
60 MYA |
K/Ar Radiometric and Biostratigraphy |
Early Paleocene |
Brown, 1962; Larsen & Drexler, 1988 |
| Denver Basin |
68 MYA |
68 MYA |
Paleomag./ Biostratigraphy |
Polarity Chron C31 Lower Maastrichtian |
Raynolds & Johnson, 2003 |
| Uinta Basin |
68 MYA |
40 MYA |
Relative Dating |
Late Cretaceous to Late Eocene |
Walton, 1964; Iaby and Picard, 1983 |
| Piceance Creek Basin |
57 MYA |
56 MYA |
Biostratigraphy |
Late Tiffanian NALMA |
Patterson et al. 2003; unpublished data |
| South Park |
66.5 MYA |
64.5 MYA |
K/Ar Radiometric Dating |
Late Cretaceous/Early Paleocene |
Marvin et al. 1978 |
| San Luis Valley |
? MYA |
? MYA |
? |
Pre-Eocene ? |
Brister & Gries, 1996; Tandon et al. 1999 |
| Raton Basin |
68 MYA |
65 MYA |
Relative Dating/ Biostratigraphy |
Late Cretaceous (Maastrichian) |
Pillmore & Flores, 1998 |
| San Juan Basin |
~68 MYA |
~61 MYA |
Relative Dating / Biostratigraphy |
Late Cretaceous to Middle Paleocene |
Newman, 1986 |
|
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