M. Venkateshwarlu , A.V. Satyakumar , N. Ramesh Babu , Anoop Kumar Singh
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Extrapolating the optically stimulated luminescence (OSL) dates from literature indicates that the entire section was probably deposited between 38 and 0.8 ka. The rock magnetic data shows that the remanence is carried by a low coercivity mineral and a significant amount of a soft magnetic mineral, most likely magnetite. Virtual Geomagnetic Pole (VGP) latitudes were calculated. Plot of the VGP latitudes against the sample locations from the litho-column allows us for the construction of Magnetic Polarity Stratigraphy (MPS) column. The MPS of the Ramganga paleolake has detected three geomagnetic excursions that are correlated with the global events: the Mono Lake Event (∼28.4-25.8 ka), the Gulf of Mexico Event (∼12.5–17 ka), and the Bagwalipokar Excursion Events (15.5-14.7 ka and 8-2.85 ka) respectively. 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引用次数: 0
摘要
沉积物中的古地磁记录为研究地磁场在不同地质年代的变化提供了基础。在此,我们报告了来自印度西北喜马拉雅山脉拉姆甘加古湖第四纪沉积物的新的古地磁数据,以深入了解全球地磁偏移及其对古环境的影响。在位于小喜马拉雅山脉 798 米高处的 Ramganga 古湖(29°46′867″N; 79°14′043″E),对 5 米厚的未固结沉积物垂直剖面进行了古地磁和岩石磁分析。根据文献中的光激发发光(OSL)日期推断,整个剖面可能沉积于 38 至 0.8 ka 之间。岩石磁性数据显示,剩磁由低矫顽力矿物和大量软磁矿物(很可能是磁铁矿)携带。计算了虚拟地磁极(VGP)纬度。将虚拟地磁极纬度与岩性柱中的样本位置相对照,可以构建磁极地层(MPS)柱。拉姆甘加古湖的磁极地层检测到三次地磁偏移,分别与全球事件相关:莫诺湖事件(28.4-25.8 ka)、墨西哥湾事件(12.5-17 ka)和巴格瓦利波卡偏移事件(15.5-14.7 ka 和 8-2.85 ka)。古湖的中下部代表了潮湿和干旱气候条件下沉积物沉积过程中的低能量和高能量沉积环境。
Magnetic polarity stratigraphy of quaternary sediments from Ramganga paleolake, NW Himalaya, India and its paleoenvironmental implications
Paleomagnetic records from the sediments provide the foundation for studying variations in the geomagnetic field across the geological time sacle. Here, we report a new paleomagnetic data from Quaternary sediments of Ramganga Paleolake, NW Himalaya, India, to provide more insight into the global geomagnetic excursions and paleoenvironmental implications. Paleomagnetic and rock magnetic analyses were performed on a 5 m thick vertical profile of unconsolidated sediments from the Ramganga paleolake (29°46′867″N; 79°14′043″E), located in the Lesser Himalaya at a height of 798 m. One hundred fifty oriented samples from 50 sites (10 cm intervals) were obtained from the vertical section. Extrapolating the optically stimulated luminescence (OSL) dates from literature indicates that the entire section was probably deposited between 38 and 0.8 ka. The rock magnetic data shows that the remanence is carried by a low coercivity mineral and a significant amount of a soft magnetic mineral, most likely magnetite. Virtual Geomagnetic Pole (VGP) latitudes were calculated. Plot of the VGP latitudes against the sample locations from the litho-column allows us for the construction of Magnetic Polarity Stratigraphy (MPS) column. The MPS of the Ramganga paleolake has detected three geomagnetic excursions that are correlated with the global events: the Mono Lake Event (∼28.4-25.8 ka), the Gulf of Mexico Event (∼12.5–17 ka), and the Bagwalipokar Excursion Events (15.5-14.7 ka and 8-2.85 ka) respectively. The lower and middle portion of the paleolake represents the low and high energy depositional environment during the sediment deposition due to wet and arid climatic conditions.