Paleobathymetry reconstructions during the Mesozoic and uncertainties in oceanic gateway evolution

The reconstruction of paleobathymetry, in particular the evolution of oceanic gateways, has important implications for paleo-ocean circulation, paleoclimate, as well as biotic and faunal exchanges. During the past ~250 million years there have been major changes in paleobathymetry and oceanic gateways associated with the breakup of the Pangaea supercontinent, including the development of the North and South Atlantic ocean basins and the Central Atlantic seaway. Considerable research effort has been invested into better understanding the global evolution of paleobathymetry and oceanic gateways during the Cenozoic, but there remain large uncertainties about the timing of opening, closure, and physiographic evolution of Mesozoic oceanic gateways and seaways.

Here, we present new paleobathymetry reconstructions based on a recent global plate tectonic model (Müller et al., 2019) spanning the Triassic (~250 Ma) to the present. We reconstruct presently-preserved oceanic crust using new functionality developed in pybacktrack v1.4, a python module for backstripping and reconstructing paleobathymetry. For present-day submerged continental crust we use pybacktrack to reconstruct paleobathymetry based on its rifting and deformation history and assuming a single lithology for the progressive decompaction of sediments. In regions where ancient seafloor is now subducted, we use an established approach of synthetically reconstructing paleobathymetry based on the age-area distribution of oceanic crust (‘age grids’) convolved with an age-depth relationship to reconstruct basement depths followed by modelling effects from sediment thickness and seafloor volcanism including large igneous provinces. Our methodology additionally allows for alternative plate tectonic models (and/or absolute reference frames) to be integrated into reconstructions of paleobathymetry. Further, we use our new paleobathymetry reconstructions to explore the formation and evolution of pre-Cenozoic oceanic gateways. We find significant differences in the development and physiography of Mesozoic oceanic gateways and seaways in our new reconstructions compared to a widely used paleogeographic model, which has major implications for paleoceanographic models and interpretations of paleoclimate proxies.