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Bioerosion pattern in a nearshore setting as a tool to disentangle multiphase transgressive episodes
Palaeogeography, Palaeoclimatology, Palaeoecology ( IF 2.6 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.palaeo.2020.109820
Alice Giannetti , Santiago Falces-Delgado , José Francisco Baeza-Carratalá

Abstract Palaeoichnology is known to be a powerful tool for the characterisation of unconformity surfaces. In a Neogene post-orogenic basin of the Betic domain (Alicante, SE Spain), a complex Miocene transgressive event on an exposed Eocene succession is recorded. The resulting unconformity surface as well as the overlying beds resulting from the establishment of a nearshore environment are ichnologically and palaeoecologically analysed. Different boring structures related to the Entobia ichnofacies were observed on a variety of substrates, including i) the rocky Eocene substrate, ii) Tortonian conglomerates and breccias, iii) oyster and coral patches (mainly represented by Tarbellastraea). Boring structures are mainly represented by Gastrochaenolites, Entobia and, more rarely, Trypanites and Spirolites? Different colonization patterns were identified, including truncated Gastrochaenolites and Entobia that are extensively developed on the Eocene rockground, small-sized Entobia, and superficial bioerosion on conglomerates and breccias, and Gastrochaenolites hospitium on corals; a selective colonization of G. hospitium was observed, with Tarbellastraea much more intensively bioeroded than Porites. Finally, the integration of stratigraphic, palaeoecological and ichnological data allowed for the identification of three different phases in the Miocene transgression: i) slow transgression with the consequent colonization of the Eocene rockground, the production of a wide planar surface and the truncated Gastrochaenolites-Entobia assemblage; ii) the breaking of this uniform coastal setting into areas characterized by different hydrodynamics, with coral development where turbulence was higher; this second phase was of limited temporal extension, with a limited accommodation space; iii) a final phase characterized by a new transgressive pulse leading to the establishment firstly of a restricted inner platform and secondarily of a slightly deeper sandy platform; in this phase, bioerosion was limited to shells, while soft- and loose-ground burrows as Ophiomorpha developed within the substrate.

中文翻译:

近岸环境中的生物侵蚀模式作为解开多相海侵事件的工具

摘要 古人类学是表征不整合面的有力工具。在 Betic 域(西班牙东南部阿利坎特)的新近纪造山后盆地中,记录了在暴露的始新世序列上发生的复杂中新世海侵事件。对由此产生的不整合面以及近岸环境建立所产生的上覆层进行了历史学和古生态学分析。在各种基底上观察到与 Entobia 地层相相关的不同钻孔结构,包括 i) 岩石始新世基底,ii) Tortonian 砾岩和角砾岩,iii) 牡蛎和珊瑚斑块(主要以 Tarbellastraea 为代表)。钻孔结构主要以 Gastrochaenolites、Entobia 为代表,更罕见的是,锥虫和螺石?确定了不同的殖民模式,包括在始新世岩地上广泛发育的截断的 Gastrochaenolites 和 Entobia,小型的 Entobia,砾岩和角砾岩上的表面生物侵蚀,以及珊瑚上的 Gastrochaenolites hospitium;观察到 G. hospitium 的选择性定植,其中 Tarbellastraea 比 Porites 受到更强烈的生物侵蚀。最后,地层学、古生态学和地质学数据的整合允许识别中新世海侵的三个不同阶段:i) 缓慢的海侵导致始新世岩地的殖民化,产生了宽阔的平面和截断的 Gastrochaenolites-Entobia装配; ii) 将这种统一的海岸环境分为具有不同流体动力学特征的区域,珊瑚发育的湍流程度更高;第二阶段时间延伸有限,住宿空间有限;iii) 以新的海侵脉冲为特征的最后阶段,首先导致建立一个受限的内部平台,其次是一个稍深的沙质平台;在这个阶段,生物侵蚀仅限于贝壳,而随着 Ophiomorpha 在基质内发育,软土和松散地面洞穴。iii) 以新的海侵脉冲为特征的最后阶段,首先导致建立一个受限的内部平台,其次是一个稍深的沙质平台;在这个阶段,生物侵蚀仅限于贝壳,而随着 Ophiomorpha 在基质内发育,软土和松散地面洞穴。iii) 以新的海侵脉冲为特征的最后阶段,首先导致建立一个受限的内部平台,其次是一个稍深的沙质平台;在这个阶段,生物侵蚀仅限于贝壳,而随着 Ophiomorpha 在基质内发育,软土和松散地面洞穴。
更新日期:2020-09-01
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