کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5785717 | 1640179 | 2017 | 17 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Geochemical characterization of the Jurassic Amran deposits from Sharab area (SW Yemen): Origin of organic matter, paleoenvironmental and paleoclimate conditions during deposition
ترجمه فارسی عنوان
مشخصات ژئوشیمیایی رسوبات عمران ژوراسیک از منطقه شاراب (یونان یون): منشاء مواد آلی، شرایط پالووآنتیو و پائول کللیمات در طی رسوب
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
زمین شناسی
چکیده انگلیسی
Calcareous shales and black limestones of the Jurassic Amran Group, located in the Sharab area (SW Yemen), were analysed based on organic and inorganic geochemical methods. The results of this study were used to reconstruct the paleoenvironmental and paleoclimatic conditions during Jurassic time and their relevance to organic matter enrichment during deposition of the Amran calcareous shale and black limestone deposits. The analysed Amran samples have present-day TOC and Stotal content values in the range of 0.25-0.91Â wt % and 0.59-4.96Â wt %, respectively. The relationship between Stotal and TOC contents indicates that the Jurassic Amran deposits were deposited in a marine environment as supported by biomarker environmental indicators. Biomarker distributions also reflect that the analysed Amran deposits received high contributions of marine organic matter (e.g., algal and microbial) with minor amount of land plant source inputs. Low oxygen (reducing) conditions during deposition of the Jurassic Amran deposits are indicated from low Pr/Ph values and relatively high elemental ratios of V/Ni and V/(VÂ +Â Ni). Enrichment in the pyrite grains and very high DOPT and high Fe/Al ratios further suggest reducing bottom waters. This paleo-redox (i.e., reducing) conditions contributed to preservation of organic matter during deposition of the Jurassic Amran deposits. Semi-arid to warm climatic conditions are also evidenced during deposition of the Amran sediments and consequently increased biological productivity within the photic zone of the water column during deposition. Therefore, the increased bio-productivity in combination with good preservation of organic matter identified as the major mechanisms that gave rise to organic matter enrichment. This contradicts with the low organic matter content of the present-day TOC values of less than 1%. The biomarker maturity data indicate that the analysed Amran samples are of high thermal maturity; therefore, the low present-day TOC is attributed to the thermal effect on the original organic matter. This high thermal maturity level is due to the presence of volcanic rocks, which have invaded the Jurassic rocks during Late Oligocene to Early Miocene.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of African Earth Sciences - Volume 129, May 2017, Pages 579-595
Journal: Journal of African Earth Sciences - Volume 129, May 2017, Pages 579-595
نویسندگان
Mohammed Hail Hakimi, Wan Hasiah Abdullah, Yousif M. Makeen, Shadi A. Saeed, Hitham Al-Hakame, Tareq Al-Moliki, Kholah Qaid Al-Sharabi, Baleid Ali Hatem,