The BASE-LiNE Earth project focused on the interaction of the dissolved main (e.g. Mg, Ca) and trace elements (e.g. Li, B, Sr) with marine life. One of the BASE-LiNE Earth work packages dealt with the complex interaction of two long term geological processes on earth: (i) by the plate tectonic and the spreading rates of the mid-ocean ridges and (ii) the rate of continental uplift weathering. The understanding of such long-term processes is essential in order to understand the environmental situation today and allows a forecast of the future. In particular, both sources and sinks for all substances are dissolved in the oceans and/or present in the earth’s atmosphere. In particular, the balance between these two processes determines the concentration of the most important greenhouse gas on earth, carbon dioxide (CO2), which in turn controls global temperatures in the ocean-atmosphere system, and thus the earth’s climate. Continental movement due to plate tectonic, changes of biological primary productivity, ocean water carbonate mineralogy, sea-level changes, glacial/interglacial cycles and/or bolide impacts superimpose the major processes causing glacial/interglacial temperature cyclicity, biological mass-extinction events and fundamental changes of the chemical and isotope composition of ocean water.
The variations of the alkaline earth elements (e.g. Mg, Ca, Sr) are particularly interesting to earth system and life sciences because these elements are most abundant and vital for the evolution of marine life, especially for the calcifying organisms in the ocean. From empirical data and numerical modeling it is known that the concentrations of Ca, Mg and Sr in seawater have varied considerably during the Phanerozoic. In turn, major changes in the balance between the oceanic hydrothermal and the carbonate/dolomite burial fluxes have sensitively influenced oceanic inventories of alkaline earth elements and their isotope systems. Importantly, shifting equilibria between continental weathering fluxes and hydrothermal and/or sedimentary (carbonate, dolomite) fluxes, modulate the evolution of marine Mg/Ca and Sr/Ca ratios over geological time. Determining the biological, environmental and tectonic processes that are responsible for these changes, will improve our understanding of the factors that control chemical composition of the ocean-atmosphere system, and thus the earth’s climate.
