Rebelo A C, Meireles R P, Barbin V, Neto A I, Melo C, Ávila S P
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.
Universidade Federal de Santa Catarina, Laboratório de Oceanografia Costeira, Florianópolis, SC, Brazil.
Micron. 2016 Jan;80:112-21. doi: 10.1016/j.micron.2015.10.004. Epub 2015 Oct 19.
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.
钙质化石作为古环境指标应用时，需要了解其成岩历史。在本研究中，对来自亚速尔群岛（东北大西洋）的上新世石枝藻进行了阴极发光显微镜（CL显微镜）和背散射电子图像-能量色散X射线光谱（BSE-EDS显微镜）分析，以便进一步了解藻类藻体中微量元素含量的分布情况，并确定古环境解释。获得了两种类型的发光：（1）高发光和（2）低发光。高发光的石枝藻与海水中高浓度的Mn(2+)有关，低发光的石枝藻与海水中低浓度的Mn(2+)有关。当石枝藻在约4.0-4.5 Ma沉积时，圣玛丽亚岛的海岸线形态与今天大不相同。熔岩和相关产物的喷出及/或活跃的浅水热液喷口的存在所导致的火山活动影响，反映在海水化学中，该岛同期的古海岸具有高浓度的海水中Mn(2+)，这反映在石枝藻的高Mn(2+)浓度上。相比之下，位于距海岸约2.8和2.9 km处、海水Mn(2+)浓度较低区域的石枝藻发光较低，反映了海水中低浓度的Mn(2+)。石枝藻的化学数据和该岛的地质历史被证明与石枝藻形成时圣玛丽亚岛的古地理重建一致。
