Abstract
The age of the ocean floor and its time-dependent age distribution control fundamental features of the Earth, such as bathymetry, sea level and mantle heat loss. Recently, the development of increasingly sophisticated reconstructions of past plate motions has provided models for plate kinematics and plate boundary evolution back in geological time. These models implicitly include the information necessary to determine the age of ocean floor that has since been lost to 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 Paleozoic, are published without an accompanying set of age models for oceanic lithosphere. Here we present an automatic, tracer-based algorithm that generates seafloor age grids from global plate tectonic reconstructions with defined plate boundaries. Our method enables us to produce novel seafloor age models for the Paleozoic’s lost ocean basins. Estimated changes in sea level based on bathymetry inferred from our new age grids show good agreement with sea level record estimations from proxies, providing a possible explanation for the peak in sea level during the assembly phase of Pangea. This demonstrates how our seafloor age models can be directly compared with observables from the geologic record that extend further back in time than the constraints from preserved seafloor. Thus, our new algorithm may also aid the further development of plate tectonic reconstructions by strengthening the links between geological observations and tectonic reconstructions of deeper time.
Highlights
The discovery of a method to determine the age of the presentday oceanic crust, using reversals of the Earth’s magnetic field (Vine and Matthews, 1963), gave rise to the recognition that the seafloor is spreading, and to the development and broad acceptance of plate tectonics
Example applications include the estimation of paleobathymetry, sea level change (Müller et al, 2008b), global seafloor heat flow (Loyd et al, 2007; Crameri et al, 2019), and the subduction volume flux, which impacts geomagnetic reversals (Hounslow et al, 2018), the thermal structure of paleo-subduction zones (Maunder et al, 2019), transport of water (Karlsen et al, 2019a) and carbon (Merdith et al, 2019) to the deep mantle, and the slab pull force on tectonic plates (Conrad and Lithgow-Bertelloni, 2004; Faccenna et al, 2012)
While the information needed to compute seafloor ages is implicitly available, the presently-established workflows to retrieve and process this information are time-consuming, laborious and not publicly available. This emphasizes the need for a method that can automatically generate seafloor age grids from full-plate tectonic reconstructions
Summary
The discovery of a method to determine the age of the presentday oceanic crust, using reversals of the Earth’s magnetic field (Vine and Matthews, 1963), gave rise to the recognition that the seafloor is spreading, and to the development and broad acceptance of plate tectonics. A wealth of information, mainly from marine geophysical data, and from the geology of continental margins, have been used to reconstruct the extent and age distribution of oceanic lithosphere of the past, including portions that have been subducted (Müller et al, 2008b). These ‘‘paleo-seafloor age grids’’ present rich new opportunities for scientific inquiry, as a wide range of Earth processes can be further interrogated with the use of such age grids. Seafloor ages for past times are important as a boundary condition for global mantle convection models (Gurnis et al, 2012)
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