کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6430975 1634853 2010 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Geomagnetic paleointensity deduced for the last 300 kyr from Unzen Volcano, Japan, and the dipolar nature of the Iceland Basin excursion
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
Geomagnetic paleointensity deduced for the last 300 kyr from Unzen Volcano, Japan, and the dipolar nature of the Iceland Basin excursion
چکیده انگلیسی

We have conducted paleointensity measurements of lavas and pyroclastic flows from Unzen Volcano, Japan. They have been shown in a previous study to contain a record of Brunhes Chron secular variation, with one flow recording a transitional direction (Senbongi geomagnetic excursion; 191 ± 17 ka). Various rock magnetic analyses indicate that the main magnetic carriers of samples are Ti-poor titanomagnetites, which have mixtures of single domain (SD) (and/or pseudo-SD) and multi-domain grain sizes. The low-temperature demagnetization (LTD)-double heating test (DHT) Shaw method yielded 209 successful results from 56 sites, giving 27 acceptable site-mean paleointensities for the past 5-300 kyr. When excluding the Senbongi excursion data and two other data points, the data give an average virtual dipole moment (VDM) of 7.69 × 1022 A m2 with a standard deviation of 2.51 × 1022 A m2 (N = 24). This is consistent with the selected 80 site-mean Thellier paleointensity data from the latest paleointensity database, with an average VDM of 7.64 × 1022 A m2 and a standard deviation of 2.56 × 1022 A m2. Paleointensity measurements on samples that record the Senbongi excursion, which is claimed to correlate with the Iceland Basin excursion, provide a value of 7.74-9.37 μT using the LTD-DHT Shaw method. This corresponds to an average (standard deviation) VDM of 2.19 × 1022 A m2 (0.21 × 1022 A m2). When calibrating sedimentary records that capture the Iceland Basin excursion by averaging the LTD-DHT Shaw VDMs obtained from the pre- and post-excursional period, the records give consistent VDM values with the volcanic (Senbongi) record during the excursion. This indicates that variation of the geomagnetic field direction and intensity during the Iceland Basin excursion can be well represented by a simple dipolar variation.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 293, Issues 3–4, 1 May 2010, Pages 236-249
نویسندگان
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