Lacasse, Christian M.; Bogaard, Paul; Garbe-Schoenberg, Carl-Dieter (1999): Record of explosive volcanism and climate change in the North Atlantic during the last 6 Myr. Geological Society of America (GSA), Boulder, CO, United States, In: Anonymous, Geological Society of America, 1999 annual meeting, 31 (7), 313-314, georefid:2001-019278
Abstract:
A composite record of explosive volcanism in the North Atlantic for the last 6 Myr is presented based on the recovery of marine tephra layers at five ODP sites. Age control of about 50 major explosive eruptions was derived from the revised magnetic stratigraphy. Planktonic and benthic oxygen isotope records were used to refine the age model of the eruptions for the 0-1 Myr time interval. Major element analyses (EMP) of the volcanic glasses indicate either bimodal compositions (mafic and silicic) with very few intermediate glasses, or unimodal compositions. Normative compositions (CIPW) of silicic glasses are compared with those obtained from a geochemical database of central volcanoes. The tephra were mostly derived from eruptions along the main rift system and the off-rift volcanic zones in Iceland, and to a lesser extent from the Jan Mayen area. The 3.0-3.6 Myr period is characterized by the highest occurrence frequency of marine tephra with one major explosive event recorded every 40 kyr on average. Comparison with climate proxy records clearly shows that this widespread record of explosive volcanism overlaps the time of onset of glaciation in the North Atlantic. Grain-size analyses of the tephra fall layers indicate that they are derived from eruptions of magnitude larger than any known historical event, or alternatively from enhanced airborne transport. Similarity coefficients of major element composition were calculated between the different pairs of silicic glasses and sorted according to increasing eruption age. High similarity coefficients (>95) over time suggest that several eruptions likely originated from the same silicic sources in Iceland. Preliminary results from Ar/Ar dating experiments on the tephra are presented to better constrain the age of the eruptions. Trace element analyses (ICP-MS) of the silicic tephra are also carried out to study the periodic activity that was inferred to some of the volcanic sources.
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West: -80.0000 East: 20.0000 North: 75.0000 South: .0000
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