First Appearance Datums (FADs) of selected acritarch taxa and correlation between Lower and Middle Ordovician stages

• Autores: Servais, Thomas; Molyneux, Stewart G.; Li, Jun; Nowak, Hendrik; Rubinstein, Claudia Viviana; Vecoli, Marco; Wang, Wen Hui; Jan, Kui
• Año de publicación: 2018
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Acritarchs; Biostratigraphy; Dapingian; Darriwilian; Floian; Ordovician; Tremadocian
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

First Appearance Datums (FADs) of selected, easily recognizable acritarch morphotypes are assessed to determine their potential contribution to correlation between Lower and Middle Ordovician stages and substage divisions along the Gondwanan margin (Perigondwana) and between Perigondwana and other palaeocontinents. The FADs for 19 genera, species and species groups are recorded throughout their biogeographical ranges. The taxa investigated fall into three groups. Some have FADs at about the same level throughout their biogeographical ranges and are useful for long-distance and intercontinental correlation. Among these are Coryphidium, Dactylofusa velifera, Peteinosphaeridium and Rhopaliophora in the upper Tremadocian Stage; Arbusculidium filamentosum, Aureotesta clathrata simplex and Coryphidium bohemicum in the lower–middle Floian Stage; Dicrodiacrodium in the upper Floian Stage; Frankea in the Dapingian–lower Darriwilian stages; and Orthosphaeridium spp., with FADs in the Dapingian–lower Darriwilian stages of Perigondwanan regions and at about the same level in Baltica. Other taxa, however, have diachronous (or apparently diachronous) FADs, and this needs to be taken into account when using them for correlation. A second group of genera and species, comprising Striatotheca, the Veryhachium lairdii group and the V. trispinosum group, have a recurring pattern of FADs in the Tremadocian Stage on Avalonia and in South Gondwana and West Gondwana, but in the Floian Stage of South China and East Gondwana. The third group, consisting of Arkonia, Ampullula, Barakella, Dasydorus, Liliosphaeridium and Sacculidium, have FADs that are markedly diachronous throughout their biogeographical ranges, although the global FADs of Arkonia, Ampullula, Liliosphaeridium and Sacculidium are apparently in South China and/or East Gondwana. It is possible that diachronous FADs are only apparent and an artefact of sampling. Nevertheless, an alternative interpretation, suggested by recurring patterns, is that some as yet undetermined factor controlled a slower biogeographical spread over time, resulting in diachroneity.
Fil: Servais, Thomas. Universite Lille; Francia
Fil: Molyneux, Stewart G.. British Geological Survey; Reino Unido
Fil: Li, Jun. Chinese Academy of Sciences; China
Fil: Nowak, Hendrik. Museo di Scienze Naturali dell'Alto Adige; Italia. Universite Lille; Francia
Fil: Rubinstein, Claudia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina
Fil: Vecoli, Marco. Biostratigraphy Group. Geological Technical Services Division; Arabia Saudita
Fil: Wang, Wen Hui. South University Changsha; China
Fil: Jan, Kui. Chinese Academy of Sciences Nanjing; China