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Bottom- and pore-water oxygenation during the early Toarcian Oceanic Anoxic Event (T-OAE) in the Asturian Basin (N Spain): Ichnological information to improve facies analysis
Sedimentary Geology ( IF 2.8 ) Pub Date : 2021-04-17 , DOI: 10.1016/j.sedgeo.2021.105909
Javier Fernández-Martínez , Francisco J. Rodríguez-Tovar , Laura Piñuela , Francisca Martínez-Ruiz , José C. García-Ramos

Detailed bed-by-bed ichnological and sedimentological analysis of the early Toarcian Oceanic Anoxic Event (T-OAE) in two sections from the Asturian Basin – Rodiles and Lastres – reveals changes in the macrobenthic tracemaker community mainly induced by oxygen fluctuations. Ichnological analysis enabled us to document an abundant and diverse trace fossil assemblage, with ten ichnogenera, probably corresponding to alternations between the Zoophycos ichnofacies and the distal expression of the Glossifungites ichnofacies: Arenicolites, Chondrites, Diplocraterion, Halimedides, Palaeophycus, Planolites, Rhizocorallium, Thalassinoides, Trichichnus and Zoophycos. Six ichnofabrics were differentiated: laminated?, DiplocraterionThalassinoides, Chondrites-mottled, ChondritesPalaeophycusPlanolites, ChondritesHalimedidesPlanolites and Chondrites-laminated. Ichnological features (including ichnodiversity, distribution of traces and cross-cutting relationships) allowed us to characterise a well-developed multi-tiered macrobenthic tracemaker community, as well as distinguish different tiering models associated with variations in bottom- and pore-water oxygenation. Anoxic conditions associated with the T-OAE corresponded mainly, but not exclusively, to black shale facies. Minor-order oxygen fluctuations from suboxic/anoxic to disoxic/oxic conditions developed during the middle part of the T-OAE. Laminated intra-T-OAE dark and light grey marls show lithological features similar to those of bioturbated pre- and post-event marls; thus, the ichnological information provides evidence that the T-OAE had a larger effect on biota than on depositional features.



中文翻译:

阿斯图里亚斯盆地(西班牙北部)早期Toarcian海洋缺氧事件(T-OAE)期间的底部和孔隙水氧合:改善岩相分析的技术信息

在阿斯图里亚斯盆地的两个部分(Rodiles和Lastres)中,对早期Toarcian海洋缺氧事件(T-OAE)进行了逐床详细的物候学和沉积学分析,揭示了主要由氧气波动引起的大型底栖生物示踪者群落的变化。Ichnological分析使我们能够记录丰富多样的痕迹化石组合,十ichnogenera,大概相当于之间交替Zoophycos遗迹相和远端表达Glossifungites遗迹相:Arenicolites球粒陨石DiplocraterionHalimedidesPalaeophycusPlanolitesRhizocoralliumThalassinoidesTrichichnusZoophycos。六个ichnofabrics分化:层压?Diplocraterion - Thalassinoides球粒陨石-mottled,球粒陨石- Palaeophycus - Planolites球粒陨石- Halimedides - Planolites球粒陨石-层压。技术特征(包括鱼类多样性,痕迹分布和跨领域关系)使我们能够表征发达的多层大型底栖生物示踪剂群落,并区分与底部和孔隙水氧化作用相关的不同分层模型。与T-OAE相关的缺氧条件主要但并非唯一地对应于黑色页岩相。在T-OAE的中部出现了从低氧/缺氧到二氧/氧条件的次要氧波动。叠层的T-OAE内深灰色和浅灰色泥灰岩显示出与生物扰动的事件前后泥灰岩相似的岩性特征。因此,鱼类学信息提供了证据,表明T-OAE对生物群的影响大于对沉积特征的影响。

更新日期:2021-05-09
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