Abstract Ichnological data are integrated with sedimentologic data and body fossil content to reconsider the origins of the biogenic sedimentary structures in upper middle Eocene strata of Wadi El-Hitan (UNESCO universal heritage area) in Egypt. Three types of rhizoliths (Type 1 to 3) are recognized, in addition to co-occurrence of six common marine ichnogenera (Ophiomorpha, Skolithos, Thalassinoides, Palaeophycus, Teichichnus and Taenidium). Fossil content comprises bivalves (Ostrea sp., Cardia sp., Cardium sp., Carditopsis sp. and Pinna sp.), gastropods (Turritella sp.), scaphopoda (tusk shells), arthropods (crabs and Balanus sp.) and the larger foraminifer Nummulites sp. as well as bony fossils of Basilosaurus isis, Dorudon atrox, crocodiles, sharks, rays and saw fish. Facies characteristics, fossil content, rhizoliths and invertebrate trace-fossil suites imply a bay-margin origin of the plant-and animal-associated biogenic sedimentary structures. Importantly, characteristics such as downward tapering and/or branching into smaller branches in addition to external and internal ornamentations are used to distinguish rhizoliths from burrows. Comparison between modern mangrove environments (i.e., substrates, fauna and flora) with the examined biogenic sedimentary structures can be used to support the marginal marine mangrove-swamp origin. Importantly, living mangrove roots are characteristically associated with marine bioturbation, which can be compared to the structures reported in the Eocene bioturbated bed. Large vertical Type-1 rhizoliths are interpreted as mangrove tree trunks. Type-2 rhizoliths correspond to prop/stilt roots similar to those of living Rhizophora sp. and locally to pneumatophore / anchor roots of living Avicennia sp. Type-3 rhizoliths are ascribed to sea-grasses roots and / or tertiary roots and root hairs. The examined compound biogenic sedimentary structures represent an excellent example for distinguishing previously misinterpreted plant roots (rhizoliths) from animal trace fossils (burrows) in marine setting as well as recognizing mangrove rhizoliths in the rock record.

中文翻译：

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埃及法尤姆 Wadi El-Hitan 世界遗产区始新世地层复合生物沉积结构的起源：是否有红树林根？

摘要 将地质学数据与沉积学数据和体化石含量相结合，重新考虑埃及Wadi El-Hitan（联合国教科文组织世界遗产区）中始新世中上层生物沉积结构的起源。除了六种常见的海洋鱼属（蛇形纲、Skolithos、Thalassinoides、Palaeophycus、Teichichnus 和 Taenidium）同时出现之外，还识别出三种类型的根石（类型 1 至 3）。化石含量包括双壳类动物（牡蛎属、蛴螬属种、Cardium sp.、Carditopsis sp. 和 Pinna sp.）、腹足类（Turritella sp.）、scaphopoda（象牙壳）、节肢动物（螃蟹和 Balanus sp.）和更大的有孔虫 Nummulites sp. 以及 Basilosaurus isis、Dorudon atrox、鳄鱼、鲨鱼、鳐鱼和锯鱼的骨化石。相特征、化石含量、根石和无脊椎动物的微量化石组暗示了与植物和动物相关的生物沉积结构的海湾边缘起源。重要的是，除了外部和内部装饰之外，诸如向下逐渐变细和/或分支成更小的分支等特征被用来区分根石和洞穴。现代红树林环境（即底物、动物群和植物群）与所检查的生物沉积结构之间的比较可用于支持边缘海洋红树林沼泽的起源。重要的是，活的红树林根系特征性地与海洋生物扰动有关，这可以与始新世生物扰动床中报道的结构进行比较。大型垂直 1 型根石被解释为红树林树干。2 型根石对应于类似于活的 Rhizophora sp. 的支柱/高跷根。和局部到活体 Avicennia sp. 的 pneumatophore / 锚根。3 型根石归因于海草根和/或第三根和根毛。检查的复合生物沉积结构代表了一个很好的例子，用于区分先前被误解的植物根（根石）和海洋环境中的动物痕迹化石（洞穴），以及识别岩石记录中的红树林根石。