A full global geodynamical model over 600 million years （Ma） has been de- veloped at the University of Lausanne during the past 20 years. We show herein how the 2D maps were converted into 3D （i.e., full hypsometry...A full global geodynamical model over 600 million years （Ma） has been de- veloped at the University of Lausanne during the past 20 years. We show herein how the 2D maps were converted into 3D （i.e., full hypsometry and bathymetry）, using a heuristic-based approach. Although the synthetic topography may be viewed as relatively crude, it has the advantage of being applicable anywhere on the globe and at any geological time. The model allows estimating the sea-level changes throughout the Phanerozoic, with the possibility, for the first time, to flood accordingly continental areas. One of the most striking results is the good correlation with ＂measured＂ sea-level changes, implying that long-term variations are predominantly tectonically-driven. Volumes of mountain relief are also estimated through time and compared with strontium isotopic ratio （Sr-ratio）, commonly thought to reflect mountain belt erosion. The tectonic impact upon the general Sr-retio trend is shown herein for the first time, although such influence was long been inferred.展开更多
During the last decades, numerous local reconstructions based on field geol- ogy were developed at the University of Lausanne （UNIL）. Team members of the UNIL partici- pated in the elaboration of a 600 Ma to present...During the last decades, numerous local reconstructions based on field geol- ogy were developed at the University of Lausanne （UNIL）. Team members of the UNIL partici- pated in the elaboration of a 600 Ma to present global plate tectonic model deeply rooted in geological data, controlled by geometric and kinematic constraints and coherent with forces acting at plate boundaries. In this paper, we compare values derived from the tectonic model （ages of oceanic floor, production and subduction rates, tectonic activity） with a combination of chemical proxies （namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations） known to be strongly in- fluenced by tectonics. One of the outstanding results is the observation of an overall decreas- ing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend reflects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations confirms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-floor production rates are in contradiction with the steady-state model hypothesized by some.展开更多
We present coupled ocean-sea-ice simulations of the Middle Jurassic（~165 Ma） when Laurasia and Gondwana began drifting apart and gave rise to the formation of the Atlantic Ocean. Since the opening of the Proto-Carib...We present coupled ocean-sea-ice simulations of the Middle Jurassic（~165 Ma） when Laurasia and Gondwana began drifting apart and gave rise to the formation of the Atlantic Ocean. Since the opening of the Proto-Caribbean is not well constrained by geological records, configurations with and without an open connection between the Proto-Caribbean and Panthalassa are examined. We use a sea-floor bathymetry obtained by a recently developed three-dimensional（3D） elevation model which compiles geological, palaeogeographical and geophysical data. Our original approach consists in coupling this elevation model, which is based on detailed reconstructions of oceanic realms, with a dynamical ocean circulation model. We find that the Middle Jurassic bathymetry of the Central Atlantic and Proto-Caribbean seaway only allows for a weak current of the order of 2 Sv in the upper 1000 m even if the system is open to the West. The effect of closing the western boundary of the Proto-Caribbean is to increase transport related to barotropic gyres in the southern hemisphere and to change water properties, such as salinity, in the Neo-Tethys. Weak upwelling rates are found in the nascent Atlantic Ocean in the presence of this superficial current and we discuss their compatibility with deep-sea sedimentological records in this region.展开更多
文摘A full global geodynamical model over 600 million years （Ma） has been de- veloped at the University of Lausanne during the past 20 years. We show herein how the 2D maps were converted into 3D （i.e., full hypsometry and bathymetry）, using a heuristic-based approach. Although the synthetic topography may be viewed as relatively crude, it has the advantage of being applicable anywhere on the globe and at any geological time. The model allows estimating the sea-level changes throughout the Phanerozoic, with the possibility, for the first time, to flood accordingly continental areas. One of the most striking results is the good correlation with ＂measured＂ sea-level changes, implying that long-term variations are predominantly tectonically-driven. Volumes of mountain relief are also estimated through time and compared with strontium isotopic ratio （Sr-ratio）, commonly thought to reflect mountain belt erosion. The tectonic impact upon the general Sr-retio trend is shown herein for the first time, although such influence was long been inferred.
基金The Institute of Geology and Palaeontology of the University of Lausanne (UNIL)the Swiss National Fund (SNF)
文摘During the last decades, numerous local reconstructions based on field geol- ogy were developed at the University of Lausanne （UNIL）. Team members of the UNIL partici- pated in the elaboration of a 600 Ma to present global plate tectonic model deeply rooted in geological data, controlled by geometric and kinematic constraints and coherent with forces acting at plate boundaries. In this paper, we compare values derived from the tectonic model （ages of oceanic floor, production and subduction rates, tectonic activity） with a combination of chemical proxies （namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations） known to be strongly in- fluenced by tectonics. One of the outstanding results is the observation of an overall decreas- ing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend reflects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations confirms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-floor production rates are in contradiction with the steady-state model hypothesized by some.
文摘We present coupled ocean-sea-ice simulations of the Middle Jurassic（~165 Ma） when Laurasia and Gondwana began drifting apart and gave rise to the formation of the Atlantic Ocean. Since the opening of the Proto-Caribbean is not well constrained by geological records, configurations with and without an open connection between the Proto-Caribbean and Panthalassa are examined. We use a sea-floor bathymetry obtained by a recently developed three-dimensional（3D） elevation model which compiles geological, palaeogeographical and geophysical data. Our original approach consists in coupling this elevation model, which is based on detailed reconstructions of oceanic realms, with a dynamical ocean circulation model. We find that the Middle Jurassic bathymetry of the Central Atlantic and Proto-Caribbean seaway only allows for a weak current of the order of 2 Sv in the upper 1000 m even if the system is open to the West. The effect of closing the western boundary of the Proto-Caribbean is to increase transport related to barotropic gyres in the southern hemisphere and to change water properties, such as salinity, in the Neo-Tethys. Weak upwelling rates are found in the nascent Atlantic Ocean in the presence of this superficial current and we discuss their compatibility with deep-sea sedimentological records in this region.
