کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8913518 | 1640167 | 2018 | 49 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System
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کلمات کلیدی
OligotrophicMid-Miocene Climatic Optimum - اواسط میوسن بهینه آب و هواSoutheast Atlantic - جنوب شرقی اقیانوس اطلسForaminifera - روزندارانBenguela upwelling system - سیستم آپوینگینگ BenguelaContinental shelf - فلات قارهPalaeoenvironment - محیط زیست PalaeoenMiocene - میوسنNamibia - نامیبیاPleistocene - پلیستوسن
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
زمین شناسی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System](/preview/png/8913518.png)
چکیده انگلیسی
Middle Miocene to Plio-Pleistocene foraminifera provide insights into the palaeoenvironment on the northern Namibian continental shelf located at the far northern end of the present-day Benguela Upwelling System (BUS). Biostratigraphy and Strontium Isotope Stratigraphy (SIS) of the recovered basal olive-green mud unit indicate an age of 16 to 14 Ma. A sharp, erosional contact separates the basal mud from the overlying Plio-Pleistocene gravelly pelletal phosphorite sands. Grain size data, P/B ratios and benthic diversity indices indicate a change between the middle Miocene and overlying Plio-Pleistocene palaeoenvironments linked to the timing and conditions associated with the initiation of the BUS. The different lithological units and microfossil assemblages in the olive-green mud unit and the overlying pelletal phosphorite units support the late Miocene initiation of the BUS and the northwards migration of the Angola-Benguela Front. Planktic foraminifera indicate a shift from warmer surface water conditions to cooler conditions during the initiation of the BUS. Benthic palaeobathymetric ranges and P/B ratios are consistent with outer shelf water depths suggesting a deeper palaeoenvironment during the Mid-Miocene Climatic Optimum (MMCO) than today. Benthic foraminifera in the middle Miocene are dominated by large (>1â¯mm) taxa and adapted to oligotrophic environments before the initiation of the BUS. The benthic assemblage composition indicates that bottom water conditions changed to eutrophic conditions during the Plio-Pleistocene under intensified upwelling conditions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of African Earth Sciences - Volume 141, May 2018, Pages 33-48
Journal: Journal of African Earth Sciences - Volume 141, May 2018, Pages 33-48
نویسندگان
Eugene W. Bergh, John S. Compton, Peter Frenzel,