"Data on seawater composition since the start of the Phanerozoic eon ~540 million years ago provide essential information for understanding long-term chemical processes of socio-economic dimension like the evolution of life, land-ocean interaction, atmospheric chemistry, ecosystem adaptation to climate change, oceanic trace metal cycling, and for applied geological processes like the formation of submarine energy resources. Although partly known this knowledge is still limited pending new methodical prospects and innovative analytical techniques. Following this approach, the proposed ETN "BASE-LiNE Earth" will train early stage researchers (ESRs) who will extend the knowledge of the complex and long-term Phanerozoic seawater history by the determination of original proxy information preserved in reliable ancient geological archives using cutting edge technologies and experimental approaches. In order to amplify this process the ESRs will be exposed to academic and non-academic high-tech institutions linking biogeochemical research and training in biology, ecology, geochemistry as well as chemical analytics to engineering and cutting edge analytical instrumentation. Multi- and interdisciplinary environments will expose our ESRs to highly demanded transferable skills increasing their employability when it comes to job application. "BASE-LiNE Earth" will offer societally important deliverables like time series of past trace element and isotope cycling and models about ocean material fluxes in and out of the Phanerozoic Ocean. This will be shared in publications, reports and exhibitions. Interactive lecturing material will be offered for education in general and specifically for high school teachers. Through collaboration with high-tech companies the ETN will contribute to establish both, new approaches for the exploration of hydrocarbon reservoirs and innovative and sophisticated analytical instrumentation for trace element and isotope measurements."