Glendonites from an Early Jurassic methane seep — Climate or methane indicators?
Glendonites from an Early Jurassic methane seep — Climate or methane indicators?
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DOI：
10.1016/j.palaeo.2013.03.001
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
B. Teichert;F. Luppold
中科院分区：
文献类型：
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作者：
B. Teichert;F. Luppold
在德国克莱姆林根东北部的早侏罗世、晚Pliensbachian剖面（margaritatustospinatumammonite带）中，发现了三个层位，其中含有丰富的斜长石、伊凯特（CaCO 3·6 H2O）之后的方解石假像以及自生碳酸盐。这些假象以前被用作指示剂的有机和磷酸盐丰富的古环境与近冻结的底层水温度。稳定同位素测量清楚地表明，伊卡特/glendonite沉淀在甲烷渗漏的位置与甲烷营养硫酸盐还原作为触发的地球化学过程伊卡特形成在硫酸盐-甲烷界面。甲烷渗漏的终止可能导致原生矿物伊凯特的解体和后续假像的形成。重建古底水温（约。10 °C）表明温度远高于先前观察到的ikaite稳定范围（接近冰点），这就提出了一个问题，即甲烷渗漏是否是在较高温度下促进ikaite形成的独特地球化学场所。
An Early Jurassic, Late Pliensbachian section (margaritatustospinatumammonite Zone) northeast of Cremlingen, Germany, revealed three horizons with abundant glendonites, calcite pseudomorphs after ikaite (CaCO3· 6H2O), as well as authigenic carbonates. These pseudomorphs have previously been used as indicators for organic- and phosphate-rich paleoenvironments with near-freezing bottom water temperatures. Stable isotope measurements clearly show that the ikaite/glendonite was precipitated at a methane seep location with methanotrophic sulfate reduction as the triggering geochemical process for ikaite formation at the sulfate–methane interface. The termination of methane seepage probably led to the disintegration of the primary mineral ikaite and successive pseudomorph formation. Reconstructed paleo bottom water temperatures (ca. 10 °C) from belemnites and ostracods indicate temperatures well above the previously observed range of ikaite stability (near freezing), raising the question if methane seeps are distinct geochemical sites promoting ikaite formation at higher temperatures.