Abstract The paper reports rare occurrence of deep-water solemyid and lucinid bivalves from Cenozoic sequences of Outer Eastern Carpathians, Ukraine. The studied bivalves occur in the Eocene Pasichna Formation, represented by deep-water marls and pelagic limestones intercalated with thin-bedded calcareous sandstones yielding material re-deposited from shallow water. This find offered a chance to study the unaltered shell breakage pattern of these deep-burrowing solemyid bivalves buried in situ by turbidites. The breakage includes arcuate breaks representing likely syn-vivo damage related to active burrowing of the animal while telescopic breaks are most likely post-mortem distortions produced by the load of the heavy sediment covering sea bottom after a turbiditic event. Taxonomic study indicates that both solemyid and lucinid bivalves from the Eocene of the Pasichna Formation are most similar to deep-water members of their respective clades, known from roughly coeval deposits from the Tethys. The available evidence indicates that bivalves in question lived on the deep-sea muddy bottom, influenced by turbidite deposits, and were buried by them syn-vivo or early post-mortem. This is in contrast to the great majority of molluskan faunas from the Carpathian Paleogene, reworked during transport downbasin from shallow-marine settings by mass gravity flows. The detailed study of the occurrence mode of deep-water bivalves in the Carpathian part of the Tethys during the Paleogene, influenced by frequent build-up of oxygen-depleted waters, offers implications for the evolutionary histories of both groups in question. For both solemyids and lucinids, adaptations to oxygen-depleted environments are primordial, and are carried from the Silurian until today, as supported by the presented fossil and actualistic evidence. This is in contrast to their histories in high-redox potential environments, with solemyids known from cold seeps from the Devonian onwards and lucinid seep record only from the Jurassic onwards.

中文翻译：

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乌克兰外东喀尔巴阡山脉始新世深水化学共生双壳类动物的埋藏学和古生态学

摘要 该论文报道了乌克兰外东喀尔巴阡山脉新生代序列中罕见的深水双壳类和双壳类动物。研究的双壳类动物出现在始新世 Pasichna 组，以深水泥灰岩和远洋灰岩为代表，夹有薄层钙质砂岩，产生从浅水中重新沉积的物质。这一发现提供了一个机会来研究这些被浊流原位埋葬的深穴双壳类动物的未改变的壳破裂模式。断裂包括弓形断裂，代表可能与动物主动挖洞相关的体内损伤，而伸缩断裂最有可能是浑浊事件后覆盖海底的重沉积物的负载产生的死后扭曲。分类学研究表明，Pasichna 组始新世的双壳类和 lucinid 与它们各自进化枝的深水成员最相似，这些成员来自特提斯的大致同时期的沉积物。现有证据表明，所讨论的双壳类动物生活在深海泥质底部，受浊积沉积物的影响，并在同体内或死后早期被它们掩埋。这与来自喀尔巴阡古近纪的绝大多数软体动物群形成鲜明对比，这些动物群是在从浅海环境运输下盆地期间通过质量重力流重新加工的。对古近纪期间特提斯喀尔巴阡山脉深水双壳类动物的发生模式进行了详细研究，受缺氧水域频繁积聚的影响，这对所讨论的两组的进化历史提供了启示。对于梭鱼和 lucinids 来说，对缺氧环境的适应是原始的，并且从志留纪一直延续到今天，正如所提供的化石和现实证据所支持的那样。这与它们在高氧化还原电位环境中的历史形成对比，从泥盆纪开始的冷渗流中已知有梭鱼，而仅从侏罗纪开始就有 lucinid 渗流记录。