[20-3] How coccolith size changed in response to paleoenvironmental variations during the Early Aptian to Late Albian?

• Main Authors: Societa Geologica Italiana 2021, Bettoni, Chiara
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Underline Science Inc. 2021
• Subjects: North Atlantic
• Online Access: https://dx.doi.org/10.48448/p0gk-hf25; https://underline.io/lecture/33923-20-3-how-coccolith-size-changed-in-response-to-paleoenvironmental-variations-during-the-early-aptian-to-late-albianquestion

Abstract: In the geological record, calcareous nannofossils are intensively studied, because they are important palaeoecological tracers. Today, as in the past, coccolithophores are really sensitive to environmental changes. So, their growth and calcification rates could be influenced by different factors such as temperature, carbonate chemistry and/or nutrient content (i.e, Erba et al., 2010; Wulff et al., 2020). The variations in nannoplankton abundance, shape and/or coccolith size could give information of past ocean-atmosphere conditions including the amount of CO2 exchange between the ocean and the atmosphere. For this research the time interval selected is the Early Aptian to Late Albian (ca. 121-100 Ma) which was characterized by important climatic and paleoenvironmental changes including a cooling event in the early late Aptian, and two “Ocean Anoxic Events”, namely the OAE 1a and OAE 1b. Particularly, the focus is on the Aptian/Albian boundary and the Oceanic Anoxic Event 1b. The whole study interval was selected because morphometrics analyses on Biscutum constans from the Western Tethys documented relatively small sized specimens in the early late Aptian (Bottini & Faucher, 2020), followed by average size increase after OAE 1b. Here, we conduct new morphometries on species with particular affinities in temperature or fertility such as Watznaueria barnesiae (oligotrophic species), Rhagodiscus asper (warm water species), Zeugrhabdotus erectus and Biscutum constans (mesotrophic species). The aim of the study is to a) see if there are any dimensional variations in different species other than B. constans; b) investigate if the species responded to paleotemperature and paleofertility changes with size variations and c) detect if the coccolith size justifies a decrease in nannoplankton calcification and how this possibly influenced the total carbon budget. Thus, in order to reach these objectives, we studied samples from ODP Site 1049 (Proto-North Atlantic) and the Piobbico core (Umbria-Marche Basin, central Italian Apennines) and we have correlated new morphometrics data with the nannofossil abundance, temperature and fertility index. Authors:* Bettoni C.* & Bottini C.