Outcrop analogues of pockmarks and associated methane-seep carbonates: A case study from the Lower Cretaceous (Albian) of the Basque-Cantabrian Basin, western Pyrenees
Outcrop analogues of pockmarks and associated methane-seep carbonates: A case study from the Lower Cretaceous (Albian) of the Basque-Cantabrian Basin, western Pyrenees
复制标题
DOI：
10.1016/j.palaeo.2012.11.020
复制
发表时间：
2013-11-15
影响因子：
3
通讯作者：
Reitner, Joachim
中科院分区：
文献类型：
--
作者：
Agirrezabala, Luis M.;Kiel, Steffen;Reitner, Joachim
巴斯克-坎塔布连盆地（比利牛斯山西部）黑复理石群的阿尔布纪晚期深水沉积物保存了一个化石麻点区，包括甲烷渗漏碳酸盐和相关的大型动物。麻点的几何形状是从重复的透镜状浊积岩沉积与位于中心的碳酸盐体重建。早期成岩碳酸盐相，如凝块泥晶灰岩和黄色方解石，δ C-13值低至-41.6%，烃生物标志物（如2，6，10，15，19-五甲基二十烷）的C-13严重缺失，表明碳酸盐沉淀是由于甲烷的厌氧氧化。这些麻点可能是由于充气海底的脱水和脱气引起的沉降而形成的，碳酸盐体的重量可能增强了这种沉降。大型底栖动物类似于世界范围内的其他晚中生代深水甲烷渗漏，以大型Lucinid和Caspiconcha双壳类和hokkaidoconchid腹足类为主。在晚期成岩作用期间，碳酸盐三角洲O-18值被重置为-12至-10%的窄范围。剩余的孔隙空间和裂缝被焦沥青填充，另外的碳酸盐相沉淀，这可能是由于热化学硫酸盐还原过程。(C)2012爱思唯尔有限公司版权所有。
Late Albian deep-water sediments of the Black Flysch Group in the Basque-Cantabrian Basin (western Pyrenees) preserve a fossil pockmark field including methane seep carbonates and associated macrofauna. The geometry of the pockmarks is reconstructed from repeated lens-shaped turbidite deposits with centrally located carbonate bodies. Early diagenetic carbonate phases such as clotted micrite and yellow calcite with delta C-13 values as low as -41.6%, and hydrocarbon biomarkers (e.g. 2,6,10,15,19-pentamethylicosane) with strong depletions in C-13 indicate that the carbonates precipitated due to anaerobic oxidation of methane. The pockmarks probably formed due to subsidence induced by dewatering and degassing of the gas-charged seabed perhaps enhanced by the weight of the carbonate bodies. The macrofauna resembles that of other late Mesozoic deep-water methane-seeps world-wide, and is dominated by large lucinid and Caspiconcha bivalves, and hokkaidoconchid gastropods. During late diagenesis the carbonate delta O-18 values were reset to a narrow range of -12 to -10%., the remaining pore spaces and fissures were filled with pyrobitumen, and additional carbonate phases precipitated, potentially due to thermochemical sulfate reduction processes. (C) 2012 Elsevier B.V. All rights reserved.