Sea level and vertical motion of continents from dynamic earth models since the Late Cretaceous

Abstract

A B S T R A C TDynamic earth models are used to better understand the impact of mantle dynamics on the vertical motion of continents and regional and global sea level change since the Late Cretaceous. A hybrid approach combines inverse and forward models of mantle convection and accounts for the principal contributors to long-term sea level change: the evolving distribution of ocean floor age, dynamic topography in oceanic and continental regions, and the geoid. We infer the relative importance of dynamic versus other factors of sea level change, determine time-dependent patterns of dynamic subsidence and uplift of continents, and derive a sea level curve.We find that both dynamic factors and the evolving distribution of sea floor age are important in controlling sea level. We track the movement of continents over large-scale dynamic topography by consistently mapping between mantle and plate frames of reference, and we find that this movement results in dynamic subsidence and uplift of continents. The amplitude of dynamic topography in continental regions is larger than global sea level in several regions and periods, so that it has controlled regional sea level in North and South America and Australia since the Late Cretaceous, northern Africa and Arabia since the late Eocene, and Southeast Asia in the Oligocene-Miocene. Eastern and southern Africa have experienced dynamic uplift over the last 20 to 30 m.y., whereas Siberia and Australia have experienced Cenozoic tilting. The dominant factor controlling global sea level is a changing oceanic lithosphere production that has resulted in a large amplitude sea level fall since the Late Cretaceous, with dynamic topography offsetting this fall. returned to Caltech where he is currently John E. and Hazel S. Smits Professor of Geophysics and director of the Seismological Laboratory. His effort is divided between linking geodynamics and the rock record (especially stratigraphy), the basic physics of geophysical phenomena, studies of the deep interior of the Earth, and the development of new computational methods, including the GPlates package for plate tectonic modeling.

Dynamic topography of passive continental margins and their hinterlands since the Cretaceous

“…The 161 tectonic reconstruction by Gurnis et al (2012), an earlier version of the tectonic 162 reconstruction by Seton et al (2012) for the last 140 million years, is used to evaluate the 163 predictions of the mantle flow models by Spasojevic and Gurnis (2012) for the last 90 million 164…”

“…The earlier period of forward integration is 172 avoided in Model M1, a hybrid model (Spasojevic and Gurnis, 2012), as the initial global 173 mantle temperature field at present-day is estimated through a combination of seismic 174 tomographic inversions of surface and body waves using model S20RTS (Ritsema et al,175 2004) in the lower mantle and one based on Benioff zone seismicity for the upper mantle 176 seismicity. This temperature field is integrated backward using the SBI (simple backward 177 integration) method of Liu and Gurnis (2008) back to the Late Cretaceous by reversing the 178 direction of gravity and plate motions.…”

Improving global paleogeography since the late Paleozoic using paleobiology

“…This makes it difficult to convert the maps into a digital format, link them to alternative digital plate tectonic reconstructions and update them when plate motion models are improved. It is therefore challenging to use paleogeographic maps to help constrain or interpret numerical models of mantle convection that predict long-wavelength topography (Gurnis et al, 1998;Spasojevic and Gurnis, 2012) based on different tectonic reconstructions, or as an input to models of past ocean and atmosphere circulation/climate (Goddéris et al, 2014;Golonka et al, 1994) and models of past erosion/sedimentation (Salles et al, 2017).…”

Dynamic topography, gravity and the role of lateral viscosity variations from inversion of global mantle flow

“…Dynamic topography is the surface undulations induced by mantle flow (Pekeris, 1935, Parsons and Daly, 1983 and plays an important role in geodynamics through a strong influence on the total topography Gurnis, 1992, Faccenna et al, 2014), the long-term large-scale flooding history of continents (Lithgow-Bertelloni and Gurnis, 1997), global and regional relative sea-level changes (Gurnis, 1990, Moucha et al, 2008, Spasojevic and Gurnis, 2012, and the amplitude and sign of the long-wavelength geoid . Although the total topography of continents is dominated by the isostatic response of density variations within the crust and lithosphere and is mainly modulated by plate tectonics, changes in dynamic topography can significantly shift coastlines and change sediment and erosion patterns as large portions of continents are at elevations close to sea level (Flament, 2014).…”

“…Dynamic topography affects both relative and global sea levels over millions of years through the differential motion of continents over large-scale dynamic topography and through modulating ocean bathymetry. Through dynamic topography, long-term sea level variations as recorded on otherwise stable continental platforms are not a simple reflection of eustatic variations (Gurnis, 1990, Moucha et al, 2008, Spasojevic and Gurnis, 2012. Lateral variations of density within the mantle drive mantle convection, which further undulates mantle density interfaces (earth's surface, the core-mantle boundary, CMB, and any internal compositional interface).…”