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BG6.3 Biogeochemical Change in Seawater and early organisms in the Phanerozoic: reconstruction, evolution and ecological impacts |
| Convener: Anton Eisenhauer | Co-Conveners: Anna Sabbatini , Claire Rollion-Bard , Alessandra Negri , Marcus Gutjahr , Caterina Morigi |
The Phanerozoic Eon marks the beginning of the biogenic carbonate fossil record providing information about the evolution of life, the land-ocean interaction and long term climate change. The varying chemical composition of Phanerozoic seawater also contributed to the extinction of many marine species during minor and in particular the largest five mass-extinction events. Proxy information necessary to extract quantitative information is gained mainly from major and trace element ratios as well as isotopic compositions in shells and tests of calcifying organisms like brachiopods, belemnites, bivalves, corals, foraminifera and others. However, the quality and reliability of these Phanerozoic records critically depends on the ability to recover original signals which have been in thermodynamic equilibrium with the surrounding Phanerozoic seawater. This goal cannot simply be achieved because species dependent vital effects and time dependent chemical alteration among other processes superimpose the original water signal to a certain extend making time series of trace element and isotope signals difficult to interpret. Therefore the improvement of existing and the development of new technical approaches and methods are highly desirable to improve and refine our existing knowledge on the history of the chemical composition of Phanerozoic seawater. Similar important are laboratory based culturing experiments in order to decipher the pathways and processes of trace elements from seawater to the site of calcification. In this regard we invite contributions about new and refined data and/or model based information about trace element and isotope compositions and cycling in Phanerozoic seawater. A special focus is on the marine biogeochemistry around the big five mass extension events and other important transitions characterizing changing in seawater composition. Welcome are also culturing studies on those calcifying organisms serving as archives for Phanerozoic seawater proxies. Furthermore, contributions emphasizing diagenetic processes or contributions introducing improved analytical techniques and methods for a better reconstruction of Phanerozoic seawater data are also highly welcome.
| Public information: |
This session is the result of two PalaeoBiogeosciences Sessions combining Biogeochemical Change in Seawater (see Session Detail) together with the presence of Early organisms in the fossil record focusing on Foraminifera. Here follows the "Early organisms in the fossil record: paleontological aspects, evolutionary and ecological impacts" session details. They are an ecologically important group of modern heterotrophic amoeboid eukaryotes whose naked and testate ancestors are thought to have evolved ~1 Ga ago. However, the single-chambered agglutinated test of these protists is hypothesized to appear in the fossil record in the Neoproterozoic, before the rise of complex animals. In addition, the difficulty of recognizing unambiguously ancestral monothalamous foraminifera in the fossil record represents the main challenge and might be related to a combination of factors, such as preservation in the sediments, adverse palaeo-environmental conditions and the absence of clear morphological characters distinguishing them from other morphologically simple testate amoeboid eukaryotes. The aim of this session is to gather information on the earliest foraminifera (single- organic and agglutinated taxa) which so far are sparse and uncoordinated in order to understand their evolution and their relationship with modern single-chambered taxa, contextualizing scientific current results in the geo-biological field. The session is open also to every other organisms coated with a fine clay layer (i.e., bacteria, testate amoebae) to understand how and if clay might help these creatures to fossilize. For this reason, this session will integrate many disciplines, from genomics to palaeo-environmental modelling to palaeontology and geochemistry. An integrate approach based one the disciplines above will result in profound insights about lifepast, present, future representing a new frontiers in the study of foraminifera. Therefore, aim of this session is to bring together specialists across all these disciplines to provide a uniquely rich and fertile intellectual environment for the pursuit of this intrinsically interdisciplinary topic. |