The age of the ocean floor (i.e. the oceanic lithosphere) and its time-dependent distribution control fundamental features of the Earth, such as bathymetry, sea level and heat loss from the Earth’s interior. Increasingly sophisticated reconstructions of past plate motions have provided models for plate kinematics and plate boundary evolution further back in geologic time. These models implicitly include the information necessary to determine the age of ocean floor that has since been lost to the Earth’s mantle via subduction. However, due to the lack of an automated and efficient method for generating global seafloor age grids, many tectonic models, most notably those extending back into the Palaeozoic, are published without an accompanying set of ages for the oceanic lithosphere. Making reconstruction-consistent age grids publicly available would thus aid a wide range of Earth scientists, including geodynamicists, climate scientists, and palaeontologists.
Video: The novel TracTec reconstructions of seafloor age and corresponding bathymetry, inferred using the seafloor age-depth relation of Crosby and McKenzie (2009). From the bathymetry models they computed changes in mean ocean depth (red line) and compared it to Phanerozoic sea level reconstructions (blue lines) inferred from the sedimentary record (Hallam, 1992; Haq and Al-Qahtani, 2005; Haq and Schutter, 2008). YouTube link: https://youtu.be/sxlQKYDRlsE
PhD student Krister S. Karlsen, together with CEED colleagues Mat Domeier, Carmen Gaina and Clint Conrad, developed an automatic, tracer-based algorithm, called TracTec (TracerTectonics), that generates seafloor age grids from global plate tectonic reconstructions. The authors used this algorithm to produce the first seafloor age models for the Palaeozoic’s lost ocean basins (video, top left panel). From the seafloor ages, the authors can reconstruct the bathymetry of these ancient ocean basins (video, top right panel), which is useful for palaeo-climate studies and for reconstructing past sea level. Indeed, the authors’ estimates for Palaeozoic sea level change (video, lower panel, red line) show good agreement with observations of sea level inferred from sediment record (video, lower panel, blue lines), thus providing a possible explanation for an observed peak in sea level during the assembly phase of the supercontinent Pangea.
Their new publication (now In Press, Computers & Geosciences) includes global age models of the oceanic lithosphere for the past 400 million years, as well as the open-source code “TracTec” that the authors developed to generate them. The current set of age grids is based on plate kinematics from Matthews et al. (2016), but TracTec easily allows the grids to be regenerated for further iterations of global plate reconstructions and can be downloaded from: http://doi.org/10.5281/zenodo.3687548
Author contact: Krister Karlsen k[dot]s[dot]karlsen[at]geo.uio.no
Krister Karlsen, Mathew Domeier, Carmen Gaina and Clinton P. Conrad (In Press/2020) A Tracer-Based Algorithm for Automatic Generation of Seafloor Age Grids from Plate Tectonic Reconstructions. Computers & Geosciences.
Crosby, A., McKenzie, D., 2009. An analysis of young ocean depth, gravity and global residual topography. Geophysical Journal International 178 Hallam, A., 1992. Phanerozoic sea-level changes. Columbia University Press. Matthews, K.J., Maloney, K.T., Zahirovic, S., Williams, S.E., Seton, M., Mueller, R.D., 2016. Global plate boundary evolution and kinematics since the late paleozoic. Global and Planetary Change 146, 226 Haq, B.U., Al-Qahtani, A.M., 2005. Phanerozoic cycles of sea-level change on the arabian platform. GeoArabia 10, 127 Haq, B.U., Schutter, S.R., 2008. A chronology of paleozoic sea-level changes. Science 322, 64.
