Computed tomography-based quantitative characterization of the oceanfloor interface

The oceanfloor interface is topographically complex and continuously transformed by physical and biological processes. In the deep sea, marine organisms are mainly responsible for the alteration of the seafloor by grazing, digging or by forming bioconstructions. Bioturbating organisms destroy the primary sedimentary texture and change the porosity and permeability properties of sediments considerably, while for example cold-water corals build frameworks that increase the seafloor complexity, baffle bypassing sediments and their remains increase the sediment heterogeneity. Both processes have a major influence on seafloor ventilation and carbon sequestration. In classical core descriptions on split core surfaces, it is often difficult to characterise the complex 3-dimensional sediment texture produced by bioturbation and/or the coral skeletons. Especially open bioturbation burrows, which can penetrate the sediment several decimetres deep, are often overlooked due to the core splitting and preparation technic.

The main goal of the project is the application of computed-tomographic (CT) imagery to not only visualise the three-dimensional sediment fabrics but to develop methodological approaches for their quantitative assessment. Therefore, several marine sedimentary environments are investigated: (i) cold-water corals reefs; (ii) manganese noddle covered seabed (also contributing to the JPIO project Mining Impact; e.g., Vonnahme et al. 2020); (iii) salt marshes (Keshta et al. 2020; Granse et al. submitted); and (iv) Arctic shelves (e.g., Bartels et al. 2017). Special attention will be paid on the characterisation of the cold-water coral morphoplasticity, as well as the quantification of open and lithified/pyritised burrows (see also Dorador et al. 2020). The separation of litho- and bioclasts from lithified/pyritised burrows is very challenging as they exhibit similar x-ray attenuation values, so that shape parameters must be considered for their separation and quantification.

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