Palaeosecular Variation of the Geomagnetic Field in the Aleutian Islands, Alaska

Abstract

Sequences of late Tertiary to Quaternary lava flows at six Aleutian Island sites were sampled for palaeosecular variation (PSV) measurement using palaeomagnetic methods. Due to limitations in probable time span represented by each sequence of flows and statistical constraints, data from only two sites are considered in themselves to be reliable indicators of PSV. When all the data are combined to give greater statistical significance, an angular standard deviation of palaeofield directions of 6 = 10.8" is obtained. This is compatible with other Pacific Ocean PSV data and points to the persistence of the present secular variation low in this region at least into Quaternary time.

The 2008 phreatomagmatic eruption of Okmok Volcano, Aleutian Islands, Alaska: Chronology, deposits, and landform changes

“…Before and between the two caldera-forming eruptions, activity consisted largely of basaltic lava effusion, (Byers, 1959;Nye and Reid, 1986;Miller and others, 1992;Kay and Kay, 1994) including the ~2-million-year-old Ashishik basalt (Bingham and Stone, 1972). A sequence of high-MgO picritic lavas likely older than the Ashishik basalts are exposed along Cape Idak northeast of the caldera (for example, Byers, 1959;Nye and Reid, 1986).…”

Paleomagnetism of Young New Zealand Basalts and Longitudinal Distribution of Paleosecular Variation.

“…They are: Aleutian Is. (Bingham and Stone, 1972), Amsterdam I. (Watkins and Nougier, 1973), Canary Is.…”

Geologic Synthesis of Leg 19 (DSDP) Results: Far North Pacific, and Aleutian Ridge, and Bering Sea

“…are not abundant, presumably marking a period of extensive erosion subsequent to uplift and plutonism and prior to the outbreak of andesitic volcanism that began to form the ridge's chain of late Cenozoic volcanoes about 2 m.y. ago (Bingham and Stone, 1971;Marlow and others, in press).…”

“…However, adjacent to the Aleutian Ridge and Kamchatka, the infall of abundant pyroclastic debris was delayed until the Pliocene. Bingham and Stone (1971) have dated some of the oldest rocks associated with the volcanoes of the Aleutian Ridge at about 2.0 m.y., which agrees nicely with the results reported in this volume.…”