Age of Lassen Peak, California, and implications for the ages of late Pleistocene glaciations in the southern Cascade Range
Turrin, Brent D; Christiansen, Robert L; Clynne, Michael A; Champion, Duane E; Gerstel, Wendy J; Muffler, L J Patrick; Trimble, Deborah A (1998) Age of Lassen Peak, California, and implications for the ages of late Pleistocene glaciations in the southern Cascade Range. Geological Society of America Bulletin, vol.110, no.7, pp.931-945, Jul 1998
| Authors | Turrin, Brent D; Christiansen, Robert L; Clynne, Michael A; Champion, Duane E; Gerstel, Wendy J; Muffler, L J Patrick; Trimble, Deborah A |
|---|---|
| Year | 1998 |
| Title | Age of Lassen Peak, California, and implications for the ages of late Pleistocene glaciations in the southern Cascade Range |
| Source | Geological Society of America Bulletin, vol.110, no.7, pp.931-945, Jul 1998 |
| ISSN | 0016-7606 |
| GeoRef | 1998-044243 |
| Keywords | absolute age; Ar/Ar; calibration; California; Cascade Range; Cenozoic; correlation; dacites; dates; emplacement; glacial geology; glaciation; ice movement; igneous rocks; Lassen Peak; magnetization; paleomagnetism; Pleistocene; Quaternary; remanent magnetization; Shasta County California; shield volcanoes; Th/U; United States; upper Pleistocene; volcanic rocks; volcanoes |
| DOI | 10.1130/0016-7606(1998)110<0931:AOLPCA>2.3.CO;2 |
Abstract
Lassen Peak is a large volcanic dome of late Pleistocene age at the southern end of the Cascades arc. This dacitic dome has a complex phenocryst assemblage of mixed-magma origin and has been effectively dated for the first time using the super 40 Ar/ super 39 Ar technique. Emplacement of the dome occurred after an advance of late Pleistocene glaciers from an older volcanic cone to the southwest and from a large volcanic plateau to the east. Emplacement of the Lassen Peak dome before the latest major Pleistocene glaciation-correlated by previous workers with the Tioga glaciation of the Sierra Nevada-formed a high peak that intercepted some of the precipitation that previously had fed the plateau ice cap, forming a 10-km-long glacier from a cirque on the northeast side of the peak. The weighted mean super 40 Ar/ super 39 Ar age of the dacite of Lassen Peak is 28.3+ or -2.7 ka. Comparison of its remanent magnetic direction to that of sedimentary deposits at Mono Lake, California, indicates a correlation to strata of 27+ or -1 ka. The dacite of Kings Creek, which erupted from the site of Lassen Peak before a glacial advance that predated the Lassen Peak dome, overlies peat that has a U-Th-calibrated super 14 C age of 37.6+ or -0.2 ka. The dacite of Kings Creek yielded a super 40 Ar/ super 39 Ar age of 32+ or -17 ka. The paleomagnetism of this dacite is similar to that of Mono Lake sediments of 35+ or -1 ka age. Thus, a late Pleistocene glacial advance probably began in the Lassen region between about 35 and 27 ka.