Science Applications of SedDB
Sediment geochemistry is of fundamental importance to a wide range of fields in the Earth sciences. Paleoclimate research and the anthropogenic influence on the environment, for example, are of increasing importance to society. Sediment is subducted into the deep Earth, and plays a major role in convergent margin magmatism, volatile cycling, and mantle evolution, and thus is an essential for any comprehensive understanding of the Earth System.
Data repositories so far contain only a small fraction of the appropriate data, often archive data in the form of individual tables as contributed by investigators rather than integrating these datasets, and therefore do not offer the advantages now being enjoyed by the igneous geochemistry community from relational databases.
SedDB with its relational structure and the appropriate data and metadata will revolutionize the application of marine sediment geochemical data in many research fields by making all-inclusive data sets that are relevant to an investigation easily and quickly accessible in electronic format on a broad scale. Such accessibility will facilitate large-scale data integration, which is difficult under current conditions. Furthermore, the existence of such data and information system could solve the problem of journals refusing to include voluminous data tables, by establishing a central location for numerical data in a rational and accessible format.
Examples for Scientific Application of SedDB
Paleoceanography and Earth History
Marine sediments are a primary archive of past global climate, at time scales ranging from the seasonal to multi-million years. A large public investment targets understanding the climate system and determining the forcing and the amplifying functions. This research investment involves large-scale generation of data that serve as proxies for changes in such climate parameters as ocean circulation, sea-surface temperature, ice sheet volume and sea level change, biological productivity, wind dynamics and transport history, and atmospheric chemistry (e.g. CO2, CH4, and other greenhouse gasses). The seafloor also records fundamental changes in the terrestrial system as well, such as the role of weathering through time, the history of tectonic uplift, and the evolution of the biosphere (e.g., C3 and C4 plant evolution).
Considering the implications for society and future policy, it is ironic that comprehensive climate related geochemical data and metadata are among the most difficult to access. Many journals have been unwilling to publish full data tables due to cost considerations, and a large portion of the data are published only in figure form. This situation has been only minimally mitigated by the advent of electronic publishing.
Crust-Mantle Fluxes and Mass Balances
The primary plate tectonic process that links surficial processes with the deep Earth is subduction of oceanic crust and sediment. This has wide-ranging effects on the Earth System. For example, quantification is important for determining the mass balances associated with crust-mantle exchange, which affects the long-term evolution of the mantle. Subducted sediments also play key roles in the genesis of some mantle plumes and convergent margin volcanics.
Understanding the balance between elements being subducted, the fluxes directly back to the surface through arc volcanism, and those to the deep mantle through recycling of the subduction-modified mantle wedge or the oceanic crust, is key for understanding how the Earth works, and a focus of the Subduction Factory portion of the MARGINS Program. Whereas reasonably complete records of the geochemistry of arc volcanics and back arc basin basalts can be obtained through PetDB, GEOROC and NAVDAT, respectively, the absence of a comparable source for the chemistry data on sediments near the associated trenches means that individual PI’s still need to compile the data themselves. The lack of availability of marine sediment data is substantially inhibiting the development of comprehensive models for crust-mantle exchange associated with plate convergence that are fundamental for understanding of the Earth System.
Geochemical Processes On and In the Seafloor
In addition to being an archive of Earth History, the seafloor is a biogeochemical membrane, through which pass chemical species on their diffusive journey between the effectively infinite reservoirs of seawater and the igneous basement, and within which a complex milieu of biogeochemical reactions occur that involve multiple examples of solid phase dissolution and re-precipitation (“diagenesis”). The seafloor thus serves as a terrific natural laboratory to study the behavior of elemental and isotopic systems over long time frames and under low-T conditions.
Because the delivery of material to the seafloor is controlled by biological productivity, eolian inputs, and authigenic uptake from seawater and porewater, there is a wide variety of lithologies and host matrices that are of prime interest to sedimentary geochemists, including biogenic sediment (carbonate, opal, phosphatic, and organic-rich), silicates (red-, green-, and brown clays that form under widely varying environments), and metal-rich materials (Mn-nodules, micronodules, crusts, coatings, metalliferous-hydrothermal sediments). Indeed, the breadth of these matrices, and the scientific issues that target them, is at times intimidating – but the unifying common denominator is that they rely on data sets that must be (1) accessible, (2) high quality, (3) verifiable, and (4) linked to appropriate metadata. The power promised by the “PetDB model” regarding geochemical relational databases will contribute greatly to these fields.