New age dates from Grande Ronde lavas, Columbia River Basalts: implications for periodicity of flood basalt eruptions and duration of major pulses
Abstract
The Grande Ronde Basalt (GRB) lavas represent the most voluminous eruptive phase of the Columbia River-Snake River-Yellowstone hotspot volcanism. This formation dominates the stratigraphy and thickness of the Columbia River Basalt Group (CRBG). GRB lavas form 66 % of the total volume of lava in the CRBG, with an estimated eruptive volume of ~150,000 cubic kilometers (km), out of a total erupted lava volume of 234,000 cubic km [Camp et al., 2003]. Recently, estimates of total eruptive duration of less than 1 Ma for highly voluminous episodes of flood basalt volcanism have been proposed from other flood basalt provinces, e.g., the 65 Ma Deccan Traps [Chenet et al., 2008]. We present new Ar-Ar ages for GRB lavas that reveal that they were emplaced within a surprisingly short maximum time range of 250 kyr. A well-documented stratigraphy for the GRB lavas [Reidel et al., 1989] shows that the formation consists of at least 50 individual eruption packages, which, when considered over a 250 kyr interval, suggests an average inter-eruption interval of 5000 years, assuming a small total duration for the eruptions (5000 yrs). Fifty to 75 eruptions in the 2000 to 3000 cubic km size-range would build up the 1-2 km-thick GR pile in the suggested time interval. In reality, some eruptions likely followed the previous one by a short but indeterminable time interval, whilst others may have had hiatuses between them of up to 10,000 years [Jolley et al., 2008]. Resolving the time intervals that elapsed between flood basalt eruptions remains vital to a better assessment of the environmental impact of this end-member style of volcanism. Other studies have shown that both CRBG and Deccan eruptions were both very high magnitude and prodigious producers of volcanic gas, most significantly sulphur dioxide. However, the cumulative effect of a series of eruptions on the environment can only be evaluated if the time-intervals elapsed between eruptions are better understood.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.V53A2127B
- Keywords:
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- 1115 Radioisotope geochronology;
- 8400 VOLCANOLOGY;
- 8425 Effusive volcanism;
- 8486 Field relationships (1090;
- 3690)