K-Ar ages of Pleistocene lava dams in the Grand Canyon in Arizona
Dalrymple, G Brent; Hamblin, W K (1998) K-Ar ages of Pleistocene lava dams in the Grand Canyon in Arizona. Proceedings of the National Academy of Sciences of the United Statesof America, vol. 95, no. 17, pp.9744-9749, 18 Aug 1998
| Authors | Dalrymple, G Brent; Hamblin, W K |
|---|---|
| Year | 1998 |
| Title | K-Ar ages of Pleistocene lava dams in the Grand Canyon in Arizona |
| Source | Proceedings of the National Academy of Sciences of the United Statesof America, vol. 95, no. 17, pp.9744-9749, 18 Aug 1998 |
| Publisher | National Academy of Sciences, Washington, DC, United States (USA) |
| ISSN | 0027-8424 |
| GeoRef | 2008-085393 |
| Keywords | absolute age; Ar-38; Ar-40; argon; Arizona; basalt flows; basalticcomposition; Cenozoic; Coconino County Arizona; Colorado River; cores;dams; dates; erosion; eruptions; Grand Canyon; isotopes; K/Ar; LavaButte Dam; lava dams; lava flows; Mohave County Arizona; noble gases;Pleistocene; Prospect Dam; Quaternary; radioactive isotopes; samples;stable isotopes; United States |
Abstract
At least 13 times during the Pleistocene Epoch lava flowed into theinner gorge of the Grand Canyon and formed lava dams, as high as 600m, that temporarily blocked the flow of the Colorado River. K-Ar ageson these lava dams indicate that the seven youngest formed within ashort period of time between about 0.6 and 0.4 mega-annum (Ma). Thephysiography of the lava dam remnants within the canyon shows thateach dam was destroyed by erosion, the Colorado River rapidly reachingits pre-existing grade level, before the next dam was emplaced by neweruptions. The total time for emplacement and destruction for anindividual lava dam was probably as little as 0.01-0.02 million years.The K-Ar ages of the two oldest dams, the Lava Butte dam (0.577 + or -0.054 Ma) and the Prospect dam (0.684 + or - 0.051 Ma) are somewhatyounger than the physiography of their remnants suggest.
9 samples from this reference
| Sample | Rock name | Major | Trace | Isotope |
|---|---|---|---|---|
| Prospect | Basalt | |||
| Lava Butte | Basalt | |||
| Whitmore | Basalt | |||
| Ponderosa | Basalt | |||
| D | Basalt | |||
| Layered Diabase | Basalt | |||
| Massive Diabase | Basalt | |||
| Toroweap Valley | Basalt | |||
| Prospect dike | Basalt |