Fossil cold seep assemblages in shallow water deposits do occur in regressive facies !?

根据物种组成、发生方式和古水深分布，日本化石化学自养组合可分为三种类型。第1型通常以囊壳类双壳类和/或管蠕虫为主，其特点是在深水环境中以异地或准异地的方式发生，并伴有构造或沉积学诱发的构造，如断层、滑坡、底辟岩或泥石流。一些1型组合与日本周围深度超过500米的现代冷渗群落相当，生活在陡坡和距石矿床上，而其他1型组合似乎与天然气水合物剧烈分解引起的斜坡破坏和沉积物崩塌有关。2型组合也以vesicomyid双壳类为主，但通常种类不同于1型。与第1型组合相比，第2型组合的特点是在水深超过1000米的泥质沉积物中原生产状。3型组合以Lucinoma和/或Conchocele为主，其特征是在水深小于300 m的泥质沉积物中土生土长。在日本周围海域还没有观察到与2型和3型组合相媲美的生物群落。值得注意的是，在2型和3型化石位置及其周围，没有观察到构造或沉积引起的构造，如断层、滑坡和/或泥石流沉积，尽管泥质沉积物有时显示角化相，表明甲烷的爆炸性流出。类型2和类型3的出现可能与引发甲烷水合物分解和/或甲烷气体向上运移的海平面变化同步。这个有效的假设也可以解释为什么没有由这些类型组成的可比较的现代群落：与第2类和第3类化石组合繁盛时的古代海平面相比，现在的海平面是稳定的。少

Fossil chemoautotrophic assemblages in Japan can be divided into three types, based on species composition, mode of occurrence, and palaeobathymetric distribution. Type 1 is dominated commonly by vesicomyid bivalves and/or tube worms, and characterised by its allochthonous or parautochthonous mode of occurrence in deep-water settings, along with tectonically-or sedimentologically-induced structures such as faults, slumps, diapirs, or debris flows. Some Type 1 assemblages are comparable to modern cold-seep communities around Japan at depths of more than about 500 m, living on scarps and talus deposits, whereas other Type 1 assemblages are seemingly related to slope failures and sediment collapses caused by the drastic decomposition of gas hydrates. Type 2 assemblages are also dominated by vesicomyid bivalves, but usually the species differ from those in Type 1. In contrast with Type 1 assemblages, Type 2 assemblages are characterised by autochthonous occurrences in muddy sediments in le … More ss than 1,000 m water depth. Type 3 assemblages are dominated by Lucinoma and/or Conchocele and are characterised by autochthonous occurrences in muddy sediments at water depths of less than 300 m. No living community comparable with Types 2 and 3 assemblages has yet been observed in the seas around Japan. It is noteworthy that no tectonically-or sedimentologically-induced structures, such as faults, slumps and/or debris-flow deposits, have been observed in and around Type 2 and 3 fossil localities, although the muddy sediments sometimes show brecciated facies that suggest an explosive effusion of methane. Occurrences of Types 2 and 3 may have been synchronous with sea-level changes that triggered methane-hydrate decomposition and/or the upward migration of methane gas. This working hypothesis may also explain why there in no comparable modern community made up of these types : present-day sea level is stable compared to the ancient sea levels when Type 2 and 3 fossil assemblages flourished. Less