Books by Nicolas Flament
"The secular cooling of the mantle and of the continental lithosphere trigger an increase in the ... more "The secular cooling of the mantle and of the continental lithosphere trigger an increase in the area of emerged land. The corollary increase in weathering and erosion processes has major consequences for the evolution of Earth's external envelopes.
We developed a physical model to evaluate the area of emerged land as a function of mantle temperature, continental area, and of the distribution of continental elevations. Our numerical results show that less than 15% of Earth's surface consisted of emerged land by the end of the Archaean. This is consistent with many geological and geochemical observations.
To estimate the secular cooling of the continental lithosphere, we combined thermo-mechanical models with fi eld observations. Our results, constrained by geological data, suggest that the Moho temperature has decreased by ~ 200ºC over 2.7 Ga in the Pilbara Craton.
To evaluate the eff ect of continental growth on the evolution of the area of emerged land, we developed a model based on published thermal evolution models. Our results suggest that the area of emerged land was less than 5% of Earth's surface in the Archaean, and that it does not depend on crustal growth. This allows to reconcile the evolution of oceanic 87Sr/86Sr with early
crustal growth models.
Continents are enriched in phosphorus, which is essential to the biosphere. The emergence of the continents would thus have triggered an increase in the production of oxygen by photosynthetic micro-organisms, possibly contributing to the oxidation of the atmosphere 2.4 Ga ago."
Le refroidissement seculaire du manteau terrestre et de la lithosphere continentale se traduit pa... more Le refroidissement seculaire du manteau terrestre et de la lithosphere continentale se traduit par l'augmentation de la surface de terres emergees. L'augmentation corollaire des processus d'alteration et d'erosion des silicates a des consequences majeures pour les enveloppes externes.
Nous avons developpe un modele physique qui permet d'evaluer la surface de terres emergees en fonction de la temperature du manteau, de la surface totale de continents, et de la distribution des altitudes continentales. Nos resultats numeriques montrent qu'a la fin de l'Archeen, moinsde 15% de la surface terrestre etaient emergee, en accord avec nombre d'observations geologiques et geochimiques.
Pour estimer le refroidissement seculaire de la lithosphere continentale, nous avons combine des modeles thermo-mecaniques avec des observations de terrain. Nos resultats, contraints par des donnees geologiques, suggerent que la temperature au Moho a diminue de ~ 200ºC en 2,7 Ga dans le craton des Pilbaras.
Pour evaluer l'effet de la croissance continentale sur l'evolution de la surface de terres emergees, nous avons developpe un modele base sur un modele d'evolution thermique publie. Nos resultats suggerent que la surface emergee, de moins de 5% de la surface terrestre a l'Archeen, depend peu de la croissance continentale. Ceci permet de reconcilier l'evolution du 87Sr/86Sr oceanique avec une croissance continentale precoce.
Les continents sont enrichis en phosphate, element essentiel a la biosphere. Leur emergence aurait donc engendre une augmentation de la production d'oxygene par des micro-organismes photosynthetiques, contribuant ainsi a l'oxydation de l'atmosphere il y a 2,4 Ga.
Papers by Nicolas Flament
Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eust... more Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, paleoclimate and ocean circulation, deep Earth resources and to constrain and interpret the dynamic topography predicted by mantle convection models. Global paleogeographic maps have been compiled and published , but they are generally presented as static maps with varying map projections, different time intervals represented by the maps and different plate motion models that underlie the paleogeographic reconstructions. This makes it difficult to convert the maps into a digital form and link them to alternative digital plate tectonic reconstructions. To address this limitation, we develop a workflow to restore global paleo-geographic maps to their present-day coordinates and enable them to be linked to a different tectonic reconstruction. We use marine fossil collections from the Paleobiology Database to identify inconsistencies between their indicative paleoen-vironments and published paleogeographic maps, and revise the locations of inferred paleo-coastlines that represent the estimated maximum transgression surfaces by resolving these inconsistencies. As a result, the consistency ratio between the paleogeography and the paleoenvironments indicated by the marine fossil collections is increased from an average of 75 % to nearly full consistency (100 %). The pa-leogeography in the main regions of North America, South America, Europe and Africa is significantly revised, especially in the Late Carboniferous, Middle Permian, Triassic, Jurassic, Late Cretaceous and most of the Cenozoic. The global flooded continental areas since the Early Devonian calculated from the revised paleogeography in this study are generally consistent with results derived from other paleoen-vironment and paleo-lithofacies data and with the strontium isotope record in marine carbonates. We also estimate the terrestrial areal change over time associated with transferring reconstruction, filling gaps and modifying the paleogeo-graphic geometries based on the paleobiology test. This indicates that the variation of the underlying plate reconstruction is the main factor that contributes to the terrestrial areal change, and the effect of revising paleogeographic geome-tries based on paleobiology is secondary.
Keywords: New Guinea inundation history mantle flow dynamic topography paleogeography The paleoge... more Keywords: New Guinea inundation history mantle flow dynamic topography paleogeography The paleogeography of New Guinea indicates fluctuating periods of flooding and emergence since the Jurassic, which are inconsistent with estimates of global sea level change since the Eocene. The role of deep Earth dynamics in explaining these discrepancies has not been explored, despite the strongly time-dependent geodynamic setting within which New Guinea has evolved. We aim to investigate the role of subduction-driven mantle flow in controlling long-wavelength dynamic topography and its manifestation in the regional sedimentary record, within a tectonically complex region leading to orogeny. We couple regionally refined global plate reconstructions with forward geodynamic models to compare trends of dynamic topography with estimates of eustasy and regional paleogeography. Qualitative corroboration of modelled mantle structure with equivalent tomographic profiles allows us to ground-truth the models. We show that predicted dynamic topography correlates with the paleogeographic record of New Guinea from the Jurassic to the present. We find that subduction at the East Gondwana margin locally enhanced the high eustatic sea levels from the Early Cretaceous (∼145 Ma) to generate long-term regional flooding. During the Miocene, however, dynamic subsidence associated with subduction of the Maramuni Arc played a fundamental role in causing long-term inundation of New Guinea during a period of global sea level fall.
Even though it is well accepted that the Earth's surface topography has been affected by mantle-c... more Even though it is well accepted that the Earth's surface topography has been affected by mantle-convection induced dynamic topography, its magnitude and time-dependence remain controversial. The dynamic influence to topographic change along continental margins is particularly difficult to unravel, because their stratigraphic record is dominated by tectonic subsidence caused by rifting. We follow a threefold approach to estimate dynamic topographic change along passive margins based on a set of seven global mantle convection models. We first demonstrate that a geodynamic forward model that includes adiabatic and viscous heating in addition to internal heating from radiogenic sources, and a mantle viscosity profile with a gradual increase in viscosity below the mantle transition zone, provides a greatly improved match to the spectral range of residual topography end-members as compared with previous models at very long wavelengths (spherical degrees 2–3). We then combine global sea level estimates with predicted surface dynamic topography to evaluate the match between predicted continental flooding patterns and published paleo-coastlines by comparing predicted versus geologically reconstructed land fractions and spatial overlaps of flooded regions for individual continents since 140 Ma. Modelled versus geologically reconstructed land fractions match within 10% for most models, and the spatial overlaps of inundated regions are mostly between 85% and 100% for the Cenozoic, dropping to about 75–100% in the Cretaceous. Regions that have been strongly affected by mantle plumes are generally not captured well in our models, as plumes are suppressed in most of them, and our models with dynamically evolving plumes do not replicate the location and timing of observed plume products. We categorise the evolution of modelled dynamic topography in both continental interiors and along passive margins using cluster analysis to investigate how clusters of similar dynamic topography time series are distributed spatially. A subdivision of four clusters is found to best reveal end-members of dynamic topography evolution along passive margins and their hinterlands, differentiating topographic stability, long-term pronounced subsidence, initial stability over a dynamic high followed by moderate subsidence and regions that are relatively proximal to subduction zones with varied dynamic topography histories. Along passive continental margins the most commonly observed process is a gradual motion from dynamic highs towards lows during the fragmentation of Pangea, reflecting the location of many passive margins now over slabs sinking in the lower mantle. Our best-fit model results in up to 500 (±150) m of total dynamic subsidence of continental interiors while along passive margins the maximum predicted dynamic topographic change over 140 million years is about 350 (±150) m of subsidence. Models with plumes exhibit clusters of transient passive margin uplift of about 200 ± 200 m, but are mainly characterised by long-term subsidence of up to 400 m. The good overall match between predicted dynamic topography to geologically mapped paleo-coastlines makes a convincing case that mantle-driven topographic change is a critical component of relative sea level change, and indeed the main driving force for generating the observed geometries and timings of large-scale continental inundation through time.
Northern Africa underwent widespread inundation during the Late Cretaceous. Changes in eustasy do... more Northern Africa underwent widespread inundation during the Late Cretaceous. Changes in eustasy do not explain the absence of this inundation across the remainder of Africa, and the timing and location of documented tectonic deformation do not explain the large-scale paleogeographic evolution. We investigate the combined effects of vertical surface displacements predicted by a series of mantle flow models and eustasy on northern African paleoenvironmental change. We compare changes in base level computed as the difference between eustasy and long-wavelength dynamic topography arising from sources of buoyancy deeper than 350 km to the evolution of paleoshorelines derived from two interpolated global data sets since the mid-Cretaceous. We also compare the predicted mantle temperature field of these mantle flow models at present-day to several seismic tomography models. This approach reveals that dynamic subsidence, related to Africa's northward motion away from the buoyant regions overlying the African large low shear velocity province, amplified sea level rise, resulting in maximum inundation of northern Africa during the Cenomanian and Turonian. By the Cenozoic, decreased magnitudes of dynamic subsidence, reflecting the reduced drawdown effects of slab material beneath northern Africa associated with the impact of the Africa-Eurasia collision, combined with a comparatively pronounced progressive sea level fall resulted in ongoing region-wide regression along coastal regions. The temporal match between our preferred model and the paleoshoreline data sets suggests that the paleogeographic evolution of this region since the Late Cretaceous has mainly been influenced by the interplay between eustasy and long-wavelength dynamic topography arising from large-scale, subduction-driven, lower mantle convection.
Keywords: New Guinea inundation history mantle flow dynamic topography paleogeography The paleoge... more Keywords: New Guinea inundation history mantle flow dynamic topography paleogeography The paleogeography of New Guinea indicates fluctuating periods of flooding and emergence since the Jurassic, which are inconsistent with estimates of global sea level change since the Eocene. The role of deep Earth dynamics in explaining these discrepancies has not been explored, despite the strongly time-dependent geodynamic setting within which New Guinea has evolved. We aim to investigate the role of subduction-driven mantle flow in controlling long-wavelength dynamic topography and its manifestation in the regional sedimentary record, within a tectonically complex region leading to orogeny. We couple regionally refined global plate reconstructions with forward geodynamic models to compare trends of dynamic topography with estimates of eustasy and regional paleogeography. Qualitative corroboration of modelled mantle structure with equivalent tomographic profiles allows us to ground-truth the models. We show that predicted dynamic topography correlates with the paleogeographic record of New Guinea from the Jurassic to the present. We find that subduction at the East Gondwana margin locally enhanced the high eustatic sea levels from the Early Cretaceous (∼145 Ma) to generate long-term regional flooding. During the Miocene, however, dynamic subsidence associated with subduction of the Maramuni Arc played a fundamental role in causing long-term inundation of New Guinea during a period of global sea level fall.
The present-day seismic structure of the mantle under the North Atlantic Ocean indicates that the... more The present-day seismic structure of the mantle under the North Atlantic Ocean indicates that the Iceland hotspot represents the surface expression of a deep mantle plume, which is thought to have erupted in the North Atlantic domain during the Palaeocene. The spatial and temporal evolution of the plume since its eruption is still highly debated , and little is known about its deep mantle history. Here, we use palaeogeographically constrained global mantle flow models to investigate the evolution of deep Earth flow beneath the North Atlantic since the Jurassic. The models show that over the last ∼ 100 Myr a remarkably stable pattern of convergent flow has prevailed in the lowermost mantle near the tip of the African Large Low-Shear Velocity Province (LLSVP), making it an ideal plume nucleation site. We extract model dynamic topography representative of a plume beneath the North Atlantic region since eruption at ∼ 60 Ma to present day and compare its evolution to available offshore geological and geophysical observations across the region. This comparison confirms that a widespread episode of Palaeocene transient uplift followed by early Eocene anomalous subsidence can be explained by the mantle-driven effects of a plume head ∼ 2500 km in diameter, arriving beneath central eastern Greenland during the Palaeocene. The location of the model plume eruption beneath eastern Green-land is compatible with several previous models. The predicted dynamic topography is within a few hundred metres of Palaeocene anomalous subsidence derived from well data. This is to be expected given the current limitations involved in modelling the evolution of Earth's mantle flow in 3-D, particularly its interactions with the base of a heterogeneous lithosphere as well as short-wavelength advective upper mantle flow, not captured in the presented global models.
Recent studies of the past eastern Australian landscape from present-day longitudinal river profi... more Recent studies of the past eastern Australian landscape from present-day longitudinal river profiles and from mantle flow models suggest that the interaction of plate motion with mantle convection accounts for the two phases of large-scale uplift of the region since 120 Ma. We coupled the dynamic topography predicted from one of these mantle flow models to a surface process model to study the evolution of the eastern Australian landscape since the Jurassic Period. We varied the rainfall regime, erodibility, sea level variations, dynamic topography magnitude, and elastic thickness across a series of experiments. The approach accounts for erosion and sedimentation and simulates catchment dynamics. Despite the relative simplicity of our model, the results provide insights on the fundamental links between dynamic topography and continental-scale drainage evolution. Based on temporal and spatial changes in longitudinal river profiles as well as erosion and deposition maps, we show that the motion of the Australian plate over the convecting mantle has resulted in significant reorganization of the eastern Australian drainage. The model predicts that the Murray river drained eastward between 150 and $120 Ma, and switched to westward draining due to the tilting of the Australian plate from $120 Ma. First order comparisons of eight modeled river profiles and of the catchment shape of modeled Murray-Darling Basin are in agreement with present-day observations. The predicted denudation of the eastern highlands is compatible with thermochronology data and sedimentation rates along the southern Australian margin are consistent with cumulative sediment thickness.
A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified ben... more A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate–mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network B22,000 km in circumference prior to 150 million years ago before migrating B1,500 km westward at an average rate of 1 cm year À 1 , indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps.
The breakup of Pangea in the Jurassic saw the opening of major ocean basins at the expense of old... more The breakup of Pangea in the Jurassic saw the opening of major ocean basins at the expense of older Tethyan and Pacific oceanic plates. Although the Tethyan seafloor spreading history has been lost to subduction, proxy indicators from multiple generations of Tethyan ribbon terranes, as well as the active margin geological histories of volcanism and ophiolite obduction events can be used to reconstruct these ancient oceanic plates. The plate reconstructions presented in this study reconcile observations from ocean basins and the onshore geological record to provide a regional synthesis, embedded in a global plate motion model, of the India-Eurasia convergence history, the accretionary growth of Southeast Asia and the Tethyan-Pacific tectonic link through the New Guinea margin.
The global plate motion model presented in this study captures the time-dependent evolution of plates and their tectonic boundaries since 160 Ma, which are assimilated as surface boundary conditions for numerical experiments of mantle convection. We evaluate subducted slab locations and geometries predicted by forward mantle flow models against P- and S-wave seismic tomography models. This approach harnesses modern plate reconstruction techniques, mantle convection models with imposed one-sided subduction, and constraints from the surface geology to address a number of unresolved Tethyan geodynamic controversies. Our synthesis reveals that north-dipping subduction beneath Eurasia in the latest Jurassic consumed the Meso-Tethys, and suggests that northward slab pull opened the younger Neo-Tethyan ocean basin from ~ 155 Ma. We model the rifting of ‘Argoland’, representing the East Java and West Sulawesi continental fragments, as a northward transfer of continental terranes in the latest Jurassic from the northwest Australian shelf – likely colliding first with parts of the Woyla intra-oceanic arc in the mid-Cretaceous, and accreting to the Borneo (Sundaland) core by ~ 80 Ma. The Neo-Tethyan ridge was likely consumed along an intra-oceanic subduction zone south of Eurasia from ~ 105 Ma, leading to a major change in the motion of the Indian Plate by ~ 100 Ma, as observed in the Wharton Basin fracture zone bends.
We investigate the geodynamic consequences of long-lived intra-oceanic subduction within the Neo-Tethys, requiring a two-stage India-Eurasia collision involving first contact between Greater India and the Kohistan-Ladakh Arc sometime between ~ 60 and 50 Ma, followed by continent-continent collision from ~ 47 Ma. Our models suggest that the Sunda slab kink beneath northwest Sumatra in the mantle transition zone results from the rotation and extrusion of Indochina from ~ 30 Ma. Our results are also the first to reproduce the enigmatic Proto South China Sea slab beneath northern Borneo, as well as the Tethyan/Woyla slab that is predicted at mid-mantle depths south of Sumatra. Further east, our revised reconstructions of the New Guinea margin, notably the evolution of the Sepik composite terrane and the Maramuni subduction zone, produce a better match with seismic tomography than previous reconstructions, and account for a slab at ~ 30°S beneath Lake Eyre that has been overridden by the northward advancing Australian continent. Our plate reconstructions provide a framework to study changing patterns of oceanic circulation, long-term sea level driven by changes in ocean basin volume, as well as major biogeographic dispersal pathways that have resulted from Gondwana fragmentation and accretion of Tethyan terranes to south- and southeast-Eurasia.
The Sundaland continental promontory, as the core of Southeast Asia, is one of the lowest lying c... more The Sundaland continental promontory, as the core of Southeast Asia, is one of the lowest lying continental regions, with half of the continental area presently inundated by a shallow sea. The role of mantle convection in driving long-wavelength topography and vertical motion of the lithosphere in this region has often been ignored when interpreting regional stratigraphy, including a widespread Late Cretaceous-Eocene unconformity, despite a consensus that Southeast Asia is presently situated over a large-amplitude, dynamic topography low resulting from long-term post-Pangea subduction. We use forward numerical models to link mantle flow with surface tectonics, and compare predicted trends of dynamic topography with eustasy and regional paleogeography to determine the influence of mantle convection on regional basin histories. A Late Cretaceous collision of Gondwana-derived terranes with Sundaland choked the active margin, leading to slab breakoff and a ~10-15 Myr-long subduction hiatus. Slab breakoff likely resulted in several hundred meters of dynamic uplift and emergence of Sundaland between ~80 and 60 Ma, and may explain the absence of a Late Cretaceous-Eocene sedimentary record. Renewed subduction from ~60 Ma reinitiated dynamic subsidence of Sundaland, leading to submergence from ~40 Ma despite falling long-term global sea levels. Our results highlight a complete ‘down-up-down’ dynamic topography cycle experienced by Sundaland, with transient dynamic topography manifesting as a major regional unconformity in sedimentary basins.
Volcanic hotspot tracks featuring linear progressions in the age of volcanism are typical surface... more Volcanic hotspot tracks featuring linear progressions in the age of volcanism are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth’s mantle [1]. Seismic imaging reveals that these plumes can be of deep origin [2]—probably rooted on thermochemical structures in the lower mantle [3–6]. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally [7,8], the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian–Emperor hotspot track in the Pacific Ocean remains enigmatic. Here we present palaeogeographically constrained numerical models of thermochemical convection and demonstrate that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 million years ago and 50 million years ago as a consequence of long-lasting subduction systems, unlike those in the south Pacific. These models show a sharp bend in the Hawaiian–Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. The different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 million years ago and 50 million years ago. This asymmetric deformation waned just before the Hawaiian– Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.
Large basaltic provinces as much as 15 km thick are common in Archean cratons. Many of these floo... more Large basaltic provinces as much as 15 km thick are common in Archean cratons. Many of these flood basalts erupted through continental crust but remained at sea level. Although common in the Archean record, subaqueous continental flood basalts (CFBs) are rare to absent in the post-Archean. Here we show that gravity-driven lower crustal fl ow may have contributed to maintaining Archean CFBs close to sea level. Our numerical experiments reveal that the characteristic time to remove the thickness anomaly associated with a CFB decreases with increasing Moho temperature (TM), from 500 m.y. for TM ≈ 320 °C to 1 m.y. for TM ≈ 900 °C. This strong dependency offers the opportunity to assess, from the subsidence history of CFBs, whether continental geotherms were significantly hotter in the Archean. In particular, we show that the subsidence history of the ca. 2.7 Ga upper Fortescue Group in the East Pilbara Craton, Western Australia, requires Moho temperatures >>700 °C. Applied to eight other unambiguous subaqueous Archean CFBs, our results indicate Moho temperatures >>650 °C at the time of eruption. We suggest that the decrease in the relative abundance of subaqueous CFBs over Earth’s history could reflect the secular cooling of the continental lithosphere due to the decrease in radiogenic heat production.
The pace of scientific discovery is being transformed by the availability of 'big data' and open ... more The pace of scientific discovery is being transformed by the availability of 'big data' and open access, open source software tools. These innovations open up new avenues for how scientists communicate and share data and ideas with each other and with the general public. Here, we describe our efforts to bring to life our studies of the Earth system, both at present day and through deep geological time. The GPlates Portal (portal.gplates.org) is a gateway to a series of virtual globes based on the Cesium Javascript library. The portal allows fast interactive visualization of global geophysical and geological data sets, draped over digital terrain models. The globes use WebGL for hardware-accelerated graphics and are cross-platform and cross-browser compatible with complete camera control. The globes include a visualization of a high-resolution global digital elevation model and the vertical gradient of the global gravity field, highlighting small-scale seafloor fabric such as abyssal hills, fracture zones and seamounts in unprecedented detail. The portal also features globes portraying seafloor geology and a global data set of marine magnetic anomaly identifications. The portal is specifically designed to visualize models of the Earth through geological time. These space-time globes include tectonic reconstructions of the Earth's gravity and magnetic fields, and several models of long-wavelength surface dynamic topography through time, including the interactive plotting of vertical motion histories at selected locations. The globes put the on-the-fly visualization of massive data sets at the fingertips of end-users to stimulate teaching and learning and novel avenues of inquiry.
Passive margin highlands occur on most continents on Earth and play a critical role in the cycle ... more Passive margin highlands occur on most continents on Earth and play a critical role in the cycle of weathering, erosion, and atmospheric circulation. Yet, in contrast to the well-developed understanding of collisional mountain belts, such as the Alps and Himalayas, the origin of less elevated (1–2 km) passive margin highlands is still unknown. The eastern Australian highlands are a prime example of these plateaus, but compared to others they have a well-documented episodic uplift history spanning 120 million years. We use a series of mantle convection models to show that the time-dependent interaction of plate motion with mantle downwellings and upwellings accounts for the broad pattern of margin uplift phases. Initial dynamic uplift of 400–600 m from 120–80 Ma was driven by the eastward motion of eastern Australia's margin away from the sinking eastern Gondwana slab, followed by tectonic quiescence to about 60 Ma in the south (Snowy Mountains). Renewed uplift of ∼700 m in the Snowy Mountains is propelled by the gradual motion of the margin over the edge of the large Pacific mantle upwelling. In contrast the northernmost portion of the highlands records continuous uplift from 120 Ma to present-day totalling about 800 m. The northern highlands experienced a continuous history of dynamic uplift, first due to the end of subduction to the east of Australia, then due to moving over a large passive mantle upwelling. In contrast, the southern highlands started interacting with the edge of the large Pacific mantle upwelling ∼40–50 million years later, resulting in a two-phase uplift history. Our results are in agreement with published uplift models derived from river profiles and the Cretaceous sediment influx into the Ceduna sub-basin offshore southeast Australia, reflecting the fundamental link between dynamic uplift, fluvial erosion and depositional pulses in basins distal to passive margin highlands.
The secular cooling of the Earth's mantle and the growth of the continental crust together imply ... more The secular cooling of the Earth's mantle and the growth of the continental crust together imply changes in the isostatic balance between continents and oceans, in the oceanic bathymetry and in the area of emerged continental crust. The evolution of these variables is of fundamental importance to the geochemical coupling of mantle, continental crust, atmosphere and ocean. To explore this further, we developed a model that evaluates the area of emerged continental crust as a function of mantle temperature, continental area and hypsometry.
In this paper, we investigate the continental freeboard predicted using different models for the cooling of the Earth. We show that constancy of the continental freeboard (± 200 m) is possible throughout the history of the planet as long as the potential temperature of the upper mantle was never more than 110–210 °C hotter than present. Such numbers imply either a very limited cooling of the planet or, most likely, a change in continental freeboard since the Archaean. During the Archaean a greater radiogenic crustal heat production and a greater mantle heat flow would have reduced the strength of the continental lithosphere, thus limiting crustal thickening due to mountain building processes and the maximum elevation in the Earth's topography [Rey, P. F., Coltice, N., Neoarchean strengthening of the lithosphere and the coupling of the Earth's geochemical reservoirs, Geology 36, 635–638 (2008)]. Taking this into account, we show that the continents were mostly flooded until the end of the Archaean and that only 2–3% of the Earth's area consisted of emerged continental crust by around 2.5 Ga. These results are consistent with widespread Archaean submarine continental flood basalts, and with the appearance and strengthening of the geochemical fingerprint of felsic sources in the sedimentary record from 2.5 Ga. The progressive emergence of the continents as shown by our models from the late-Archaean onward had major implications for the Earth's environment, particularly by contributing to the rise of atmospheric oxygen and to the geochemical coupling between the Earth's deep and surface reservoirs.
The history of seafloor spreading in the ocean basins provides a detailed record of relative moti... more The history of seafloor spreading in the ocean basins provides a detailed record of relative motions between Earth's tectonic plates since Pangea breakup. Determining how tectonic plates have moved relative to the Earth's deep interior is more challenging. Recent studies of contemporary plate motions have demonstrated links between relative plate motion and absolute plate motion (APM), and with seismic anisotropy in the upper mantle. Here we explore the link between spreading directions and APM since the Early Cretaceous. We find a significant alignment between APM and spreading directions at mid-ocean ridges; however, the degree of alignment is influenced by geodynamic setting, and is strongest for mid-Atlantic spreading ridges between plates that are not directly influenced by time-varying slab pull. In the Pacific, significant mismatches between spreading and APM direction may relate to a major plate-mantle reorganization. We conclude that spreading fabric can be used to improve models of APM.
The Cenozoic evolution of South American topography is marked by episodes of large-scale uplift a... more The Cenozoic evolution of South American topography is marked by episodes of large-scale uplift and subsidence not readily explained by lithospheric deformation. The drying up of the inland Pebas system, the drainage reversal of the Amazon river, the uplift of the Sierras Pampeanas and the uplift of Patagonia have all been linked to the evolution of mantle flow since the Miocene in separate studies. Here we investigate the evolution of long-wavelength South American topography as a function of subduction history in a time-dependent global geodynamic model. This model is shown to be consistent with these inferred changes, as well as with the migration of the Chaco foreland basin depocentre, that we partly attribute to the inboard migration of subduction resulting from Andean mountain building. We suggest that the history of subduction along South America has had an important influence on the evolution of the topography of the continent because time-dependent mantle flow models are consistent with the history of vertical motions as constrained by the geological record at four distant areas over a whole continent. Testing alternative subduction scenarios reveals flat slab segments are necessary to reconcile inferred Miocene shorelines with a simple model paleogeography. As recently suggested, we find that the flattening of a subduction zone results in dynamic uplift between the leading edge of the flat slab segment and the trench, and in a wave of dynamic subsidence associated with the inboard migration of the leading edge of flat subduction. For example, the flattening of the Peruvian subduction contributed to the demise of Pebas shallow-water sedimentation, while continental-scale tilting also contributed to the drainage reversal of the Amazon River. The best correlation to P-wave tomography models for the Peruvian flat slab segment is obtained for a case when the asthenosphere, here considered to be 150 km thick and 10 times less viscous than the upper mantle, is restricted to the oceanic domain.
The southwest Pacific is a frontier region for petroleum exploration. A complex series of subduct... more The southwest Pacific is a frontier region for petroleum exploration. A complex series of subduction and back-arc basin forming episodes characterises the late Cretaceous to presentday evolution of the region. Controversial aspects of the regional tectonic history include the presence or lack of subduction between 83 and 43 Ma, the polarity of subduction, the timing of back-arc basin formation, and whether or not Pacific plate motion can be tied to the motion of Australia via spreading in the Tasman Sea during the late Cretaceous-early Cenozoic. A combination of tectonic and geodynamic models has previously been used to propose that there was no subduction to the east of Australia between 83 and 43 Ma, with the Lord Howe Rise being part of the Pacific plate during this time period, contrary to alternative plate models that include a plate boundary to the east of the Lord Howe Rise. Determining which plate circuit to use for Pacific motion is critical for producing regional reconstructions for the southwest Pacific, and addressing specific problems on the chronology of tectonic and basin-forming events. To help resolve these long-standing disputes we test a recently published plate reconstruction in global mantle flow models with imposed plate motions. We use the 3D spherical mantle-convection code CitcomS coupled to the plate reconstruction software GPlates, with plate motions since 200 Ma and evolving plate boundaries imposed. We use seismic mantle tomography models to test the forward-modelled subduction history in the region. The reconstruction that we test incorporates east-dipping subduction from 85-45 Ma along the western margin of the Loyalty-Three Kings Ridge to close the South Loyalty Basin.
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Books by Nicolas Flament
We developed a physical model to evaluate the area of emerged land as a function of mantle temperature, continental area, and of the distribution of continental elevations. Our numerical results show that less than 15% of Earth's surface consisted of emerged land by the end of the Archaean. This is consistent with many geological and geochemical observations.
To estimate the secular cooling of the continental lithosphere, we combined thermo-mechanical models with fi eld observations. Our results, constrained by geological data, suggest that the Moho temperature has decreased by ~ 200ºC over 2.7 Ga in the Pilbara Craton.
To evaluate the eff ect of continental growth on the evolution of the area of emerged land, we developed a model based on published thermal evolution models. Our results suggest that the area of emerged land was less than 5% of Earth's surface in the Archaean, and that it does not depend on crustal growth. This allows to reconcile the evolution of oceanic 87Sr/86Sr with early
crustal growth models.
Continents are enriched in phosphorus, which is essential to the biosphere. The emergence of the continents would thus have triggered an increase in the production of oxygen by photosynthetic micro-organisms, possibly contributing to the oxidation of the atmosphere 2.4 Ga ago."
Nous avons developpe un modele physique qui permet d'evaluer la surface de terres emergees en fonction de la temperature du manteau, de la surface totale de continents, et de la distribution des altitudes continentales. Nos resultats numeriques montrent qu'a la fin de l'Archeen, moinsde 15% de la surface terrestre etaient emergee, en accord avec nombre d'observations geologiques et geochimiques.
Pour estimer le refroidissement seculaire de la lithosphere continentale, nous avons combine des modeles thermo-mecaniques avec des observations de terrain. Nos resultats, contraints par des donnees geologiques, suggerent que la temperature au Moho a diminue de ~ 200ºC en 2,7 Ga dans le craton des Pilbaras.
Pour evaluer l'effet de la croissance continentale sur l'evolution de la surface de terres emergees, nous avons developpe un modele base sur un modele d'evolution thermique publie. Nos resultats suggerent que la surface emergee, de moins de 5% de la surface terrestre a l'Archeen, depend peu de la croissance continentale. Ceci permet de reconcilier l'evolution du 87Sr/86Sr oceanique avec une croissance continentale precoce.
Les continents sont enrichis en phosphate, element essentiel a la biosphere. Leur emergence aurait donc engendre une augmentation de la production d'oxygene par des micro-organismes photosynthetiques, contribuant ainsi a l'oxydation de l'atmosphere il y a 2,4 Ga.
Papers by Nicolas Flament
The global plate motion model presented in this study captures the time-dependent evolution of plates and their tectonic boundaries since 160 Ma, which are assimilated as surface boundary conditions for numerical experiments of mantle convection. We evaluate subducted slab locations and geometries predicted by forward mantle flow models against P- and S-wave seismic tomography models. This approach harnesses modern plate reconstruction techniques, mantle convection models with imposed one-sided subduction, and constraints from the surface geology to address a number of unresolved Tethyan geodynamic controversies. Our synthesis reveals that north-dipping subduction beneath Eurasia in the latest Jurassic consumed the Meso-Tethys, and suggests that northward slab pull opened the younger Neo-Tethyan ocean basin from ~ 155 Ma. We model the rifting of ‘Argoland’, representing the East Java and West Sulawesi continental fragments, as a northward transfer of continental terranes in the latest Jurassic from the northwest Australian shelf – likely colliding first with parts of the Woyla intra-oceanic arc in the mid-Cretaceous, and accreting to the Borneo (Sundaland) core by ~ 80 Ma. The Neo-Tethyan ridge was likely consumed along an intra-oceanic subduction zone south of Eurasia from ~ 105 Ma, leading to a major change in the motion of the Indian Plate by ~ 100 Ma, as observed in the Wharton Basin fracture zone bends.
We investigate the geodynamic consequences of long-lived intra-oceanic subduction within the Neo-Tethys, requiring a two-stage India-Eurasia collision involving first contact between Greater India and the Kohistan-Ladakh Arc sometime between ~ 60 and 50 Ma, followed by continent-continent collision from ~ 47 Ma. Our models suggest that the Sunda slab kink beneath northwest Sumatra in the mantle transition zone results from the rotation and extrusion of Indochina from ~ 30 Ma. Our results are also the first to reproduce the enigmatic Proto South China Sea slab beneath northern Borneo, as well as the Tethyan/Woyla slab that is predicted at mid-mantle depths south of Sumatra. Further east, our revised reconstructions of the New Guinea margin, notably the evolution of the Sepik composite terrane and the Maramuni subduction zone, produce a better match with seismic tomography than previous reconstructions, and account for a slab at ~ 30°S beneath Lake Eyre that has been overridden by the northward advancing Australian continent. Our plate reconstructions provide a framework to study changing patterns of oceanic circulation, long-term sea level driven by changes in ocean basin volume, as well as major biogeographic dispersal pathways that have resulted from Gondwana fragmentation and accretion of Tethyan terranes to south- and southeast-Eurasia.
In this paper, we investigate the continental freeboard predicted using different models for the cooling of the Earth. We show that constancy of the continental freeboard (± 200 m) is possible throughout the history of the planet as long as the potential temperature of the upper mantle was never more than 110–210 °C hotter than present. Such numbers imply either a very limited cooling of the planet or, most likely, a change in continental freeboard since the Archaean. During the Archaean a greater radiogenic crustal heat production and a greater mantle heat flow would have reduced the strength of the continental lithosphere, thus limiting crustal thickening due to mountain building processes and the maximum elevation in the Earth's topography [Rey, P. F., Coltice, N., Neoarchean strengthening of the lithosphere and the coupling of the Earth's geochemical reservoirs, Geology 36, 635–638 (2008)]. Taking this into account, we show that the continents were mostly flooded until the end of the Archaean and that only 2–3% of the Earth's area consisted of emerged continental crust by around 2.5 Ga. These results are consistent with widespread Archaean submarine continental flood basalts, and with the appearance and strengthening of the geochemical fingerprint of felsic sources in the sedimentary record from 2.5 Ga. The progressive emergence of the continents as shown by our models from the late-Archaean onward had major implications for the Earth's environment, particularly by contributing to the rise of atmospheric oxygen and to the geochemical coupling between the Earth's deep and surface reservoirs.
We developed a physical model to evaluate the area of emerged land as a function of mantle temperature, continental area, and of the distribution of continental elevations. Our numerical results show that less than 15% of Earth's surface consisted of emerged land by the end of the Archaean. This is consistent with many geological and geochemical observations.
To estimate the secular cooling of the continental lithosphere, we combined thermo-mechanical models with fi eld observations. Our results, constrained by geological data, suggest that the Moho temperature has decreased by ~ 200ºC over 2.7 Ga in the Pilbara Craton.
To evaluate the eff ect of continental growth on the evolution of the area of emerged land, we developed a model based on published thermal evolution models. Our results suggest that the area of emerged land was less than 5% of Earth's surface in the Archaean, and that it does not depend on crustal growth. This allows to reconcile the evolution of oceanic 87Sr/86Sr with early
crustal growth models.
Continents are enriched in phosphorus, which is essential to the biosphere. The emergence of the continents would thus have triggered an increase in the production of oxygen by photosynthetic micro-organisms, possibly contributing to the oxidation of the atmosphere 2.4 Ga ago."
Nous avons developpe un modele physique qui permet d'evaluer la surface de terres emergees en fonction de la temperature du manteau, de la surface totale de continents, et de la distribution des altitudes continentales. Nos resultats numeriques montrent qu'a la fin de l'Archeen, moinsde 15% de la surface terrestre etaient emergee, en accord avec nombre d'observations geologiques et geochimiques.
Pour estimer le refroidissement seculaire de la lithosphere continentale, nous avons combine des modeles thermo-mecaniques avec des observations de terrain. Nos resultats, contraints par des donnees geologiques, suggerent que la temperature au Moho a diminue de ~ 200ºC en 2,7 Ga dans le craton des Pilbaras.
Pour evaluer l'effet de la croissance continentale sur l'evolution de la surface de terres emergees, nous avons developpe un modele base sur un modele d'evolution thermique publie. Nos resultats suggerent que la surface emergee, de moins de 5% de la surface terrestre a l'Archeen, depend peu de la croissance continentale. Ceci permet de reconcilier l'evolution du 87Sr/86Sr oceanique avec une croissance continentale precoce.
Les continents sont enrichis en phosphate, element essentiel a la biosphere. Leur emergence aurait donc engendre une augmentation de la production d'oxygene par des micro-organismes photosynthetiques, contribuant ainsi a l'oxydation de l'atmosphere il y a 2,4 Ga.
The global plate motion model presented in this study captures the time-dependent evolution of plates and their tectonic boundaries since 160 Ma, which are assimilated as surface boundary conditions for numerical experiments of mantle convection. We evaluate subducted slab locations and geometries predicted by forward mantle flow models against P- and S-wave seismic tomography models. This approach harnesses modern plate reconstruction techniques, mantle convection models with imposed one-sided subduction, and constraints from the surface geology to address a number of unresolved Tethyan geodynamic controversies. Our synthesis reveals that north-dipping subduction beneath Eurasia in the latest Jurassic consumed the Meso-Tethys, and suggests that northward slab pull opened the younger Neo-Tethyan ocean basin from ~ 155 Ma. We model the rifting of ‘Argoland’, representing the East Java and West Sulawesi continental fragments, as a northward transfer of continental terranes in the latest Jurassic from the northwest Australian shelf – likely colliding first with parts of the Woyla intra-oceanic arc in the mid-Cretaceous, and accreting to the Borneo (Sundaland) core by ~ 80 Ma. The Neo-Tethyan ridge was likely consumed along an intra-oceanic subduction zone south of Eurasia from ~ 105 Ma, leading to a major change in the motion of the Indian Plate by ~ 100 Ma, as observed in the Wharton Basin fracture zone bends.
We investigate the geodynamic consequences of long-lived intra-oceanic subduction within the Neo-Tethys, requiring a two-stage India-Eurasia collision involving first contact between Greater India and the Kohistan-Ladakh Arc sometime between ~ 60 and 50 Ma, followed by continent-continent collision from ~ 47 Ma. Our models suggest that the Sunda slab kink beneath northwest Sumatra in the mantle transition zone results from the rotation and extrusion of Indochina from ~ 30 Ma. Our results are also the first to reproduce the enigmatic Proto South China Sea slab beneath northern Borneo, as well as the Tethyan/Woyla slab that is predicted at mid-mantle depths south of Sumatra. Further east, our revised reconstructions of the New Guinea margin, notably the evolution of the Sepik composite terrane and the Maramuni subduction zone, produce a better match with seismic tomography than previous reconstructions, and account for a slab at ~ 30°S beneath Lake Eyre that has been overridden by the northward advancing Australian continent. Our plate reconstructions provide a framework to study changing patterns of oceanic circulation, long-term sea level driven by changes in ocean basin volume, as well as major biogeographic dispersal pathways that have resulted from Gondwana fragmentation and accretion of Tethyan terranes to south- and southeast-Eurasia.
In this paper, we investigate the continental freeboard predicted using different models for the cooling of the Earth. We show that constancy of the continental freeboard (± 200 m) is possible throughout the history of the planet as long as the potential temperature of the upper mantle was never more than 110–210 °C hotter than present. Such numbers imply either a very limited cooling of the planet or, most likely, a change in continental freeboard since the Archaean. During the Archaean a greater radiogenic crustal heat production and a greater mantle heat flow would have reduced the strength of the continental lithosphere, thus limiting crustal thickening due to mountain building processes and the maximum elevation in the Earth's topography [Rey, P. F., Coltice, N., Neoarchean strengthening of the lithosphere and the coupling of the Earth's geochemical reservoirs, Geology 36, 635–638 (2008)]. Taking this into account, we show that the continents were mostly flooded until the end of the Archaean and that only 2–3% of the Earth's area consisted of emerged continental crust by around 2.5 Ga. These results are consistent with widespread Archaean submarine continental flood basalts, and with the appearance and strengthening of the geochemical fingerprint of felsic sources in the sedimentary record from 2.5 Ga. The progressive emergence of the continents as shown by our models from the late-Archaean onward had major implications for the Earth's environment, particularly by contributing to the rise of atmospheric oxygen and to the geochemical coupling between the Earth's deep and surface reservoirs.
the thickening of the continental crust, many Archean flood basalts that show continental contamination remained
below sea level during their eruption. In this contribution, we suggest that one possible way of maintaining basaltic
piles several kilometers thick below sea level is via gravity-driven lower crustal flow of hot continental crust.
Using numerical experiments, we show that the characteristic time to remove the anomaly in crustal thickness
associated with a continental flood basalt (CFB) decreases exponentially with Moho temperature (TM) from 2.5
Gyr for TM 300 C to 5 Myr for TM 1050 C. Therefore, the removal of the thickness anomaly associated
with CFBs erupted on cold continents occurs by a combination of brittle deformation and erosion, two processes
of time scale of a few tens of million years. This is consistent with observations for Phanerozoic CFBs that are
subject to important erosion and would not be preserved in the geological record over billions of years, contrary to
subaqueous Archean CFBs. We show, based on sedimentary and structural observations, that the subsidence of the
1.4-km-thick basalts of the Kylena Formation and lower 600-m-thick basalts of the Maddina Formation in the
Meentheena Centrocline (Pilbara Craton, Western Australia) occurred without any significant tectonic extension
in 15 Myr and 11 Myr, respectively. We interpret our observations as the surface expression of the removal
of thickness anomaly by the flow of lower continental crust. From our modeling results, the subsidence of these
basalts over such time scales requires Moho temperatures 900 ºC. The example of the Fortescue Group illustrates
that thick subaqueous Archean CFBs are the result of the accumulation of several basaltic packages, each erupted
over 30 Myr. Moho temperatures 800 C are required to maintain such basaltic packages below sea level
by lower crustal flow. Thus, the prevalence of subaqueous CFBs in the Archean record suggests that they were
dominantly emplaced on hot, weak continental crust and that Archean continental geotherms were significantly
warmer than their modern counterparts.
We developed a model to evaluate the area of emerged continental crust as a function of mantle temperature, continental area and hypsometry. For constant continental hypsometry and for three different thermal evolution models, we find that a constant continental freeboard (± 200 m) throughout Earth’s history is possible as long as the potential temperature of the upper mantle never exceeded its present value by more than 110–210°C. This implies either a very limited cooling of the planet or, most likely, a change in continental freeboard since the Archaean. As for the area of emerged land, our calculations suggest that less than ~ 12% of Earth’s surface were emerged in the Archaean, compared to ~ 28% at present.
Of importance to the evolution of the area of emerged land is the shape of the continents. During the Archaean, a greater radiogenic crustal heat production and a possibly greater mantle heat flow would have reduced the strength of the continental lithosphere, thus limiting crustal thickening due to
mountain building processes and the maximum elevation in Earth’s topography (Rey and Coltice, 2008). Taking this effect into account, we show that the continents were mostly flooded until the end of the Archaean, with 2‐3% of Earth’s area emerged by 2.5 Ga. These results are consistent with the widespread occurrence of submarine continental flood basalts in the Archaean, and with the appearance and strengthening of the geochemical fingerprint of felsic sources in the sedimentary record from 2.5 Ga.
In order to investigate the influence of crustal growth models on the area of emerged land and on the evolution of oceanic 87Sr/86Sr, we developed an integrated model based on the thermal evolution model of Labrosse and Jaupart (2007). Modelling results suggest that the area of emerged land does
not closely depend on crustal growth models, and that less than 5% of Earth’s area was emerged in the Archaean. Furthermore, our models reconcile early crustal growth models with the evolution of oceanic 87Sr/86Sr as recorded by marine carbonates when a reduced emerged area and lower continental elevations are accounted for. Thus, a delayed crustal growth model is not needed to account for the observed trend in oceanic 87Sr/86Sr.
References
Labrosse, S., Jaupart, C., 2007. Thermal evolution of the Earth: Secular changes and fluctuations of plate characteristics. Earth Planet. Sc. Lett. 260, 465–481.
Rey, P. F., Coltice, N., 2008. Neoarchean strengthening of the lithosphere and the coupling of the Earth’s geochemical reservoirs. Geology 36, 635–638.
We developed a physical model to evaluate the area of emerged land as a function of mantle temperature, continental area, and of the distribution of continental elevations. Our numerical results show that less than 15% of Earth’s surface consisted of emerged land by the end of the Archaean. This is consistent with many geological and geochemical observations.
To estimate the secular cooling of the continental lithosphere, we combined thermo-mechanical models with field observations. Our results, constrained by geological data, suggest that the Moho temperature has decreased by ~ 200◦C over 2.7 Ga in the Pilbara Craton.
To evaluate the effect of continental growth on the evolution of the area of emerged land, we developed a model based on published thermal evolution models. Our results suggest that the area of emerged land was less than 5% of Earth’s surface in the Archaean, and that it does not depend on crustal growth. This allows to reconcile the evolution of oceanic 87Sr/86Sr with early crustal growth models.
Continents are enriched in phosphorus, which is essential to the biosphere. The emergence of the continents would thus have triggered an increase in the production of oxygen by photosynthetic microorganisms, possibly contributing to the oxidation of the atmosphere 2.4 Ga ago.
geodynamical phenomena, such as volcanic island chains showing an age pro-
gression. Numerical studies suggest that mantle plumes could originate deep
within the Earth, possibly at the core-mantle boundary, as a result of thermal
instabilities. Thermal buoyancy causes such plumes to rise through the man-
tle and reach the base of the lithosphere. Numerical models of mantle plumes
are routinely used to study their inception and subsequent ascent through the
mantle. Numerous 2D studies have been performed - however, the combined
effects of temperature dependent viscosity, thermal and chemical boundary
layers on plume generation and their subsequent ascent velocities are still
relatively poorly understood. Significant advances in computational capac-
ity now allow for systematic 3D studies to be undertaken at resolutions fine
enough to resolve highly convective plume features.
We first design simple 3D isoviscous regional plume models under the
Boussinesq approximation in CitcomS as a starting point, comparing results
against analytical solutions. We impose a hot sphere of radius 200 km with
an excess temperature of ~200 K - at the base of the lower mantle - to
initiate our plume models. We study the effects of mesh resolution on re-
solving fine structures of ascending plumes, along with associated return flow
as they reach the base of the lithosphere, and on that of the rate of conver-
gence to analytical solutions. Building onto these results we then investigate
the effects of thermal and chemical boundary layers, heat content and heat
distribution of the initial temperature anomaly and temperature-dependent
viscosity on the ascent velocity of plumes. In addition, we investigate the
predicted evolution of dynamic topography and surface heat flux. We will
use the results of our regional tests to devise appropriate parametrizations
to implement active upwellings in forward global mantle flow models with
compositionally distinct thermal boundary layers.