کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4690267 | 1636135 | 2009 | 14 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Intra-crater deposits of the Toga tuff ring, Oga Peninsula, NE Japan
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
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چکیده انگلیسی
The intra-crater deposit`s are exposed over a thickness of 50Â m in the deeply incised crater floor. They comprise mainly monomictic tephra of phreatomagmatic origin and are similar in grain-size distribution and sedimentary structures to relatively high and low density turbidites, although the constituents, sparse block-sag structures, and multiple fluid-escape dikes suggest that they are the subaqueous equivalents of high- and low-density pyroclastic currents with similar grain-sizes and degree of grain-size sorting. Marine diatom frustules sparsely contained in the deposits suggest that the crater was likely open to the sea, enabling rapid access of seawater to the vent. Pyroclasts ejected through the water flowed back into the crater to form eruption-fed oscillatory or circular turbidity currents and were repeatedly recycled and variably abraded by subsequent explosions, while many juvenile pumice lapilli and ash grains were carried beyond the crater rim to form relatively dilute pyroclastic currents. The Toga example suggests that primary deposits emplaced in crater lakes are well sorted, graded and stratified with polymodal flow directions, sparse block-sags, and vesicular and fragile fragments that are more or less abraded by repeated explosions and recycling.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Sedimentary Geology - Volume 220, Issues 3â4, 15 October 2009, Pages 204-217
Journal: Sedimentary Geology - Volume 220, Issues 3â4, 15 October 2009, Pages 204-217
نویسندگان
Kazuhiko Kano, Takeshi Ohguchi,