title: Diagenetic history of lower Pliocene rhodoliths of the Azores Archipelago (NE Atlantic): Application of cathodoluminescence techniques.
abstract: The diagenetic history of calcareous fossils is required for their application as palaeoenvironmental indicators. In this study, cathodoluminescence-microscopy (CL microscopy) and back scatter electron image-energy dispersive X-ray spectroscopy (BSE-EDS microscopy) were applied to Pliocene rhodoliths from the Azores Archipelago (NE Atlantic) in order to gain additional insight regarding the trace element content distribution throughout the algae thalli, and to ascertain palaeoenvironmental interpretations. Two types of luminescence were obtained: (1) high and (2) low luminescence. Rhodoliths with high luminescence are related with high concentrations of Mn(2+) in seawater and low luminescence rhodoliths are related with low concentrations of Mn(2+) in seawater. When the rhodoliths were deposited at about 4.0-4.5 Ma, the shoreline configuration of Santa Maria Island was much different than today. The influence of volcanic activity due to the extrusion of lavas and associated products and/or the presence of active shallow-water hydrothermal vents, was reflected in the sea water chemistry, with penecontemporaneous palaeoshores of the island featuring a high sea water concentration of Mn(2+), which mirrored on the rhodolith Mn(2+) high concentration. By contrast, rhodoliths located about 2.8 and 2.9 km from the shore, in areas with low seawater Mn(2+) concentration, had low luminescence, reflecting the low Mn(2+) concentration in seawater. Rhodoliths chemical data and the geological history of the island proved to be congruent with the palaeogeographical reconstruction of Santa Maria Island at the time of the formation of the rhodoliths.
authors.affiliation: Departamento de Biologia, Universidade dos Açores, Campus de Ponta Delgada, Apartado 1422-801 Ponta Delgada, Açores, Portugal; CIBIO-Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores-Departamento de Biologia da Universidade dos Açores, 9501-801 Ponta Delgada, Açores, Portugal; MPB-Marine Palaeobiogeography Working group, University of Azores, Portugal; SMNS-Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, D-70191 Stuttgart, Germany. Electronic address: acfurtadorebelo@gmail.com.
authors.forename: A C
authors.initials: AC
authors.lastname: Rebelo
authors.affiliation: Universidade Federal de Santa Catarina, Laboratório de Oceanografia Costeira, Florianópolis, SC, Brazil. Electronic address: ricomeireless@gmail.com.
authors.forename: R P
authors.initials: RP
authors.lastname: Meireles
authors.affiliation: GEGENAA, EA 3795, Université de Reims Champagne-Ardenne, France. Electronic address: vincent.barbin@univ-reims.fr.
authors.forename: V
authors.initials: V
authors.lastname: Barbin
authors.affiliation: Departamento de Biologia, Universidade dos Açores, Campus de Ponta Delgada, Apartado 1422-801 Ponta Delgada, Açores, Portugal; cE3c-Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group, and Universidade dos Açores, Departamento de Biologia, 9501-801 Ponta Delgada, São Miguel, Azores, Portugal; CIRN-Universidade dos Açores, Apartado 1422, 9501-801 Ponta Delgada, Açores, Portugal. Electronic address: aneto@uac.pt.
authors.forename: A I
authors.initials: AI
authors.lastname: Neto
authors.affiliation: MPB-Marine Palaeobiogeography Working group, University of Azores, Portugal; Departamento de Geociências-Universidade dos Açores, Apartado 1422, 9501-801 Ponta Delgada, Açores, Portugal. Electronic address: casm.azores@gmail.com.
authors.forename: C
authors.initials: C
authors.lastname: Melo
authors.affiliation: Departamento de Biologia, Universidade dos Açores, Campus de Ponta Delgada, Apartado 1422-801 Ponta Delgada, Açores, Portugal; CIBIO-Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores-Departamento de Biologia da Universidade dos Açores, 9501-801 Ponta Delgada, Açores, Portugal; MPB-Marine Palaeobiogeography Working group, University of Azores, Portugal. Electronic address: avila@uac.p.
authors.forename: S P
authors.initials: SP
authors.lastname: Ávila
mesh_terms: D001394:Azores; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry*; D008163:Luminescent Measurements / Q000379:methods*; D000461:Rhodophyta / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D014131:Trace Elements / Q000032:analysis*
chemical_list: D014131:Trace Elements
keywords: Azores Archipelago; Back scatter electron image microscope; Cathodoluminescence-microscopy; Energy dispersive X-ray spectrometer; Lower Pliocene; Rhodoliths