Magnetic mineral diagenesis in the post-glacial muddy sediments from the southeastern South Yellow Sea: Response to marine environmental changes
Magnetic mineral diagenesis in the post-glacial muddy sediments from the southeastern South Yellow Sea: Response to marine environmental changes
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DOI：
10.1360/02yd0302
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发表时间：
2005-01
期刊：
影响因子：
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通讯作者：
Jian Liu;R. Zhu;Shaoquan Li;Chang Jeong-Hae
中科院分区：
文献类型：
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作者：
Jian Liu;R. Zhu;Shaoquan Li;Chang Jeong-Hae
YSDP 1 O 3柱取自南黄海东南部冷涡下的泥质存款，其最上部29.79 m代表了13 ka BP以来陆棚内形成的泥质沉积。下部29.79 ~ 13.35英寸为A2单元，沉积时期为冰后期海侵至中全新世（约614 c ka BP）当海平面上升达到最大值时，13.35m以上上部（称为Al单元）是在冰后期海平面上升高峰后，与黄海暖流形成有关的冷涡旋中沉积的。岩石磁性的最高29.79米的核心进行了详细研究。实验结果表明，该岩芯的磁性矿物以磁铁矿、磁赤铁矿和赤铁矿为主，除上桅2.35 m外，磁性矿物均经历了还原成岩作用，磁性矿物含量和低磁性组分比例显著下降。更重要的是，在A2单元中发现了铁磁性硫化铁（硫铁矿），而在A1单元中没有，这表明海洋环境条件对磁性矿物成岩作用的控制。磁性参数在A1和A2单元之间的边界处出现突变，反映了环境条件和沉积物的主要磁性组分对成岩作用的共同影响。在单元A2中观察到高和低磁性参数的交替带，这可能是由于携带到研究区域的磁性矿物的浓度和/或粒度的周期性变化。
Core YSDPlO3 was retrieved in the muddy deposit under the cold eddy of the southeastern South Yellow Sea, and the uppermost 29.79 m core represents the muddy sediments formed in the shelf since about 13 ka BP. The lower part from 29.79 to 13.35 in, called Unit A2, was deposited during the period from the post-glacial transgression to the middle Holocene (at about 614c ka BP) when the rising sea level reached its maximum, while the upper part above 13.35 m (called Unit Al) was deposited in a cold eddy associated with the formation of the Yellow Sea Warm Current just after the peak of post-glacial sea level rise. Rock-magnetic properties of the uppermost 29.79 m core were investigated in detail. The experimental results indicate that the magnetic mineralogy of the core is dominated by magnetite, maghemite and hematite and that, except for the uppermast 2.35 m, the magnetic minerals were subject to reductive diagenesis leading to significant decline of magnetic mineral content and the proportion of low-coercivity component. More importantly, ferrimagnetic iron sulphide (greigite) is found in Unit A2 but absent in Unit Al, suggesting the control of marine environmental conditions on the magnetic mineral diagenesis. Magnetic parameters show abrupt changes across the boundary between Units A1 and A2, which reflects a co-effect of environmental conditions and primary magnetic components of the sediments on the diagenesis. Alternating zones of high and low magnetic parameters are observed in Unit A2, which is presumably due to periodic changes of the concentration and/or grain size of magnetic minerals carried into the study area.