Denver Basin Geochronology

By Darrel Dunn, Ph.D., PG, Hydrogeologist

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The following table contains my interpretation of the age of events related to the development of the Denver Basin in Colorado, USA, and the adjacent mountains.

Ma Event (Ma = Million Years before present)

0 Post-Laramide uplift continues (Tectonic and rebound due to erosion. Uplift > 5000 feet)

0.0093 Sudden cooling

0.011 End Wisconsin glaciation (Bull Lake, Pinedale, and Holocene Terraces in Denver Area)

0.1 Begin Wisconsin glaciation

Slocum Alluvium deposited (Sangoman/Illinoian)

0.25 End Illinoisian

0.4 Begin Illinoisian

0.64 Verdos gravel deposited (Age based on volcanic ash bed)

0.75 End Kansan glaciation

0.9 Begin Kansan glaciation

1.65 End Nebraskan glaciation

1.8 Begin Nebraskan glaciation

5 End Post-Laramide magmatism (Left Eocene erosional surface buried under flow and ejecta)

5.3 Beginning of Pliocene

7 Alluvial fans began to form along mountain front

10 Rate of exhumation increases

23 Beginning of Miocene

28 Begin Post-Laramide uplift, extension, and rifting

33.5 End of Eocene

36 Begin Post-Laramide magmatism, faulting, northward tilting of Denver Basin

36.7 Deposition of Castle Rock Conglomerate

37 Wall Mountain Tuff deposited

Rocky Mountain erosion surface developed (Low relief surface extends east onto deposits)

40 End of Laramide deformation and beginning of Oligocene

52 Beginning of D2 deposition

54.8 Beginning of Eocene

64 End of D1 deposition

65.5 Beginning of Paleocene

72 Beginning of Laramide deformation

75 End of Laramie Formation deposition (Laramie deposited by retreating Cretaceous sea)

510 Begin advance of Cambrian sea from west.

1100 Begin Pre-Cambrian erosional period.

Related information is contained in the web page titled Palmer Lake Geology.