Simon Williams

• PhD
• University of Tasmania

Relative plate motions during continental rifting result from the interplay of local with far-field forces. Here, we study the dynamics of rifting and breakup using large-scale numerical simulations of mantle convection with self-consistent evolution of plate boundaries. We show that continental separation follows a characteristic evolution with fo...

Most subduction zones have associated long‐wavelength anomalies in the lithospheric magnetic field observed at satellite altitude. We model the 13 subduction zones defined by seismicity and seismic tomography using vertically integrated magnetizations that are increasing, level, or decreasing away from the trench. These mimic end members of a magne...

Plate tectonics shapes Earth’s surface, and is linked to motions within its deep interior1,2. Cold oceanic lithosphere sinks into the mantle, and hot mantle plumes rise from the deep Earth, leading to volcanism3,4. Volcanic eruptions over the past 320 million years have been linked to two large structures at the base of the mantle presently under A...

Full‐plate reconstructions describe the history of past continental motions and how plate boundaries have evolved to accommodate these motions. Traditionally, tectonic reconstructions relied on geophysical data from the oceans and paleomagnetism as the primary quantitative constraints. However, these data do not directly constrain the paths of subd...

The evolving mosaic of tectonic plates across the surface of the Earth sets boundary conditions for the evolution of biotic and abiotic processes and helps shape the dynamics of its interior. Reconstructing plate tectonics back through time allows scientists from a range of disciplines (such as palaeobiology, palaeoclimate, geodynamics and seismolo...

Magnetic observations from the oceans have made fundamental contributions to our knowledge of plate motions and the evolution of the geomagnetic field over the past ∼200 Myr. Here we construct updated models of magnetization for the oceanic lithosphere, taking advantage of the most recent models for Earth's past plate motions. We then evaluate thes...

It has long been recognised that spreading ridges are kept in place by competing subduction forces that drive plate motions. Asymmetric strain rates pull spreading ridges in the direction of the strongest slab pull force, which partially explains why spreading ridges can migrate vast distances. However, the interaction between mantle plumes and spr...

The mechanisms underlying the deformation and eventual destruction of Earth’s cratons remain enigmatic, despite proposed links to subduction and deep mantle plume processes. Here we study the deformation of the North China Craton using four-dimensional mantle flow models of the plate–mantle system since the late Mesozoic, integrating constraints fr...

Serpentinization plays a central role in geological, geochemical, and microbiological processes at various depths and conditions. While mineralogical and geochemical patterns of serpentinization are known at low-pressure and temperature, equivalent processes taking place at much greater depths and elevated temperatures in subduction zones are less...

Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes includin...

Serpentinization is among the most important, and ubiquitous, geological processes in crustal–upper mantle conditions (<6 GPa, <600°C), altering the rheology of rocks and producing H2 that can sustain life. While observations are available to quantify serpentinization in terrestrial and mid‐ocean ridge environments, measurements within subduction z...

New rock dredge samples supply key information to establish the tectonic and geological framework of the northern two‐thirds of the 95% submerged Zealandia continent. The R/V Investigator voyage IN2016T01 to the Fairway Ridge, Coral Sea, obtained poorly sorted poly‐lithologic pebbly to cobbly sandstones, well sorted fine grained sandstones, mudston...

PyGPlates is an open‐source Python library to visualize and edit plate tectonic reconstructions created using GPlates. The Python API affords a greater level of flexibility than GPlates to interrogate plate reconstructions and integrate with other Python workflows. GPlately was created to accelerate spatio‐temporal data analysis leveraging pyGPlate...

Norfolk Ridge bounds the northeastern edge of the continent of Zealandia and is proximal to where Cenozoic Tonga‐Kermadec subduction initiation occurred. We present and analyze new seismic reflection, bathymetric and rock data from Norfolk Ridge that show it is composed of a thick sedimentary succession and that it was formed and acquired its prese...

Dynamics of Plate Tectonics and Mantle Convection, written by specialists in the field, gathers state-of-the-art perspectives on the dynamics of plate tectonics and mantle convection. Plate tectonics is a unifying theory of solid Earth sciences. In its initial form, it was a kinematic theory that described how the planet’s surface is fragmented int...

We evaluate four mantle convection models that use tectonic reconstructions to specify kinematic boundary conditions to explore the development of the lower mantle large low shear velocity provinces (LLSVP) structures and their relationship with mantle plumes. Evolution of mantle plumes in our spherical models is broadly consistent with observation...

The fossil record of marine invertebrates has long fuelled the debate as to whether or not there are limits to global diversity in the sea1–5. Ecological theory states that, as diversity grows and ecological niches are filled, the strengthening of biological interactions imposes limits on diversity6,7. However, the extent to which biological intera...

Understanding the long-term evolution of Earth's plate–mantle system is reliant on absolute plate motion models in a mantle reference frame, but such models are both difficult to construct and controversial. We present a tectonic-rules-based optimization approach to construct a plate motion model in a mantle reference frame covering the last billio...

The sedimentary rock record suggests that global sea levels may have fluctuated by hundreds of meters throughout Phanerozoic times. Long-term (10–80 Myr) sea level change can be inferred from paleogeographic reconstructions and stratigraphic methods can be used to estimate sea level change over 1–10 Myr in tectonically quiescent regions assumed to...

Understanding the long-term evolution of Earth's plate-mantle system is reliant on absolute plate motion models in a mantle reference frame, but such models are both difficult to construct and controversial. We present a tectonic rules-based optimisation approach to construct a plate motion model in a mantle reference frame covering the last billio...

Plain Language Summary Four billion years ago Mars had a magnetic field generated by a dynamo operating in its liquid core, as Earth has today. It cooled faster than Earth and dynamo action ceased but not before it had magnetized the planet's crust. This study is made topical by the arrival of the Chinese rover Zhurong, which is capable of carrying...

Plate tectonic regime drives the recycle and exchange of elements and energy between lithosphere and Earth surface, therefore sustaining a habitable Planet Earth, but Earth was not born with Plate tectonics. The evolution of plate tectonics is controlled by ambient mantle temperature and sediments in subduction channel. Plate tectonic regime initia...

The fossil record of marine invertebrates has long fueled the debate on whether or not there are limits to global diversity in the sea1–4⁠. Ecological theory states that as diversity grows and ecological niches are filled, the strengthening of biological interactions imposes limits on diversity5–7⁠. However, the extent to which biological interacti...

Dating the closure of the Paleo-Asian Ocean (PAO) is critical to our understanding of East Asian tectonics during the formation of Pangea, yet existing estimates differ by up to 130 Myr (380 Ma to 250 Ma). We report two robust paleomagnetic results from 320-280 Ma volcanic strata in the South Mongolia-Xing’an Belt. Stable characteristic remanences...

Full-plate reconstructions describe the history of both past continental motions and how plate boundaries have evolved to accommodate these motions. The fluxes of material into and out of the mantle at plate boundaries is thought to deeply influence the evolution of deep Earth structure, surface environments and biological systems through deep time...

Recent progress in plate tectonic reconstructions has seen models move beyond the classical idea of continental drift by attempting to reconstruct the full evolving configuration of tectonic plates and plate boundaries. A particular problem for the Neoproterozoic and Cambrian is that many existing interpretations of geological and palaeomagnetic da...

Recent progress in plate tectonic reconstructions has seen models move beyond the classical idea of continental drift by attempting to reconstruct the full evolving configuration of tectonic plates and plate boundaries. A particular problem for the Neoproterozoic and Cambrian is that many existing interpretations of geological and palaeomagnetic da...

We present an updated oceanic crustal age grid and a set of complementary grids including spreading rate, asymmetry, direction, and obliquity. Our data set is based on a selected set of magnetic anomaly identifications and the plate tectonic model of Müller et al. (2019, 10.1029/2018TC005462). We find the mean age of oceanic crust is 64.2 Myr, slig...

A major topic of debate in earth science and climate science surrounds the timing of closure of the Central American Seaway. While it is clear that the gateway was closed by ca. 2.8 Ma, recent studies based on geological and marine molecular evidence have suggested an earlier closing time of early to mid-Miocene. In this study, we examined the infl...

Reconstructions of past seafloor age make it possible to quantify how plate tectonic forces, surface heat flow, ocean basin volume and global sea-level have varied through geological time. However, past ocean basins that have now been subducted cannot be uniquely reconstructed, and a significant challenge is how to explore a wide range of possible...

Long-term variations in eustatic sea level in an ice-free world, which existed through most of the Mesozoic and early Cenozoic eras, are partly driven by changes in the volume of ocean basins. Previous studies have determined ocean basin volume changes from plate tectonic reconstructions since the Mesozoic; however, these studies have not considere...

The SW Pacific region consists of a succession of ridges and basins that were created by the fragmentation of Gondwana and the evolution of subduction zones since Mesozoic times. This complex geodynamic evolution shaped the geology of New Caledonia, which lies in the northern part of the Zealandia continent. Alternative tectonic models have been po...

The supercontinent Pangea formed by the subduction of the Iapetus and Rheic oceans between Gondwana, Laurentia, and Baltica during mid-to-late Paleozoic times. However, there remains much debate regarding how this amalgamation was achieved. Most paleogeographic models based on paleomagnetic data argue that the juxtaposition of Gondwana and Laurussi...

Relative plate motions during continental rifting result from the interplay of local with far-field forces. Here, we study the dynamics of rifting and breakup using large-scale numerical simulations of mantle convection with self-consistent evolution of plate boundaries. We show that continental separation follows a characteristic evolution with fo...

Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes. Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa. We devise paleogeographically constrained global model...

Accurately mapping plate boundary types and locations through time is essential for understanding the evolution of the plate-mantle system and the exchange of material between the solid Earth and surface environments. However, the complexity of the Earth system and the cryptic nature of the geological record make it difficult to discriminate tecton...

Subduction is a fundamental mechanism of material exchange between the planetary interior and the surface. Despite its significance, our current understanding of fluctuating subducting plate area and slab volume flux has been limited to a range of proxy estimates. Here we present a new detailed quantification of subduction zone parameters from the...

The thermo-mechanical evolution of the Earth's mantle is largely controlled by the dynamics of subduction zones, which connect the surface tectonic plates with the interior. However, little is known about the systematics of where subduction initiates and ceases within the framework of global plate motions and evolving continental configurations. He...

The ATOM low-complexity community Earth System software is designed to enable the con-struction of simple and inexpensive models for atmosphere and ocean circulation through geological time without the need for high-performance computing. ATOM solves the Low-Reynolds-Number 3-dimensional Navier-Stokes equations including transport equations for wat...

Subduction is a fundamental mechanism of material exchange between the planetary interior and the surface. Despite its significance, our current understanding of fluctuating subducting plate area and slab volume flux has been limited to a range of proxy estimates. Here we present a new detailed quantification of subduction zone parameters from the...

A widely recognised feature of the continent of Zealandia is its areally-extensive, low-volume, non-hotspot related, Late Cretaceous to Holocene intraplate magmatism. While samples are readily available from onshore regions, the offshore extent of the province, especially in northernmost Zealandia, remains poorly known. In July 2016, the ECOSATII r...

The absolute motion of tectonic plates since Pangea can be derived from observations of hotspot trails, paleomagnetism, or seismic tomography. However, fitting observations is typically carried out in isolation without consideration for the fit to unused data or whether the resulting plate motions are geodynamically plausible. Through the joint eva...

Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240...

East Asia and South America have both experienced long-term subduction since at least the Jurassic, but they have had contrasting tectonic evolutions since the Late Cretaceous. East Asia was dominated by extensional tectonics with many marginal sea basins forming during the Cenozoic while South America was dominated by compressional tectonics build...

Oblique divergence at plate boundaries is the kinematic state where the relative plate velocity is not orthogonal to the long-wavelength plate boundary trend. Previous observational and modelling studies suggest that oblique divergence strongly affects syn-rift tectonics, rifted margin formation, as well as the generation of long-offset mid-oceanic...

Global sea level change can be inferred from sequence stratigraphic and continental flooding data. These methods reconstruct sea level from peri-cratonic and cratonic basins that are assumed to be tectonically stable and sometimes called reference districts, and from spatio-temporal correlations across basins. However, it has been understood that l...

One of the world’s most notable intraplate volcanic regions lies on the eastern Australian plate and includes two age-progressive trails offshore (Tasmantid and Lord Howe seamount chains) and the world’s longest continental hotspot trail (Cosgrove Track). While most studies agree that these chains formed by the rapid northward motion of the Austral...

Forward and adjoint plate-mantle models currently represent the primary means of understanding the evolution of the plate-mantle system over time periods significantly longer than 100 Myr. These plate motion- and subduction-driven models depend on kinematic models as surface boundary constraints and are widely used for understanding plume-plate, as...

The recently released GPlates 2.0 software (www.gplates.org) provides a framework for building plate motion models including distributed extension and compression, driven by the motions of the surrounding rigid plate interiors, with constraints assimilated from well and seismic data. Here we present a regional deforming plate model for Australia an...

In October-November 2012 a geophysical mapping and dredging campaign in the eastern Coral Sea was conducted on the RV Southern Surveyor during voyage ss2012_v06 (ECOSATI). Part of this campaign was focussed in northernmost Zealandia where volcanic seamounts and uplifted portions of the Lord Howe Rise were targeted to determine the age and location...

The extent of continental rifts and subduction zones through deep geological time provides insights into the mechanisms behind supercontinent cycles and the long term evolution of the mantle. However, previous com- pilations have stopped short of mapping the locations of rifts and subduction zones continuously since the Neoproterozoic and within a...

Movements of tectonic plates often induce oblique deformation at divergent plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2-D deformation where the rift velocity is oriented perpendicular to the plate boundary. Here we quantify the validity of this assumpt...

The motion of diverging tectonic plates is typically constrained by geophysical data from preserved ocean crust. However, constraining plate motions during continental rifting and the breakup process relies on balancing evidence from a diverse range of geological and geophysical observations, often subject to differing interpretations. Reconstructi...

Numerical models of landscape evolution are playing an increasingly important role in providing an improved understanding of geomorphic transport processes shaping Earth's surface topography. Improving theoretical underpinnings coupled with increasing computational capacity has led to the development of several open source codes written in low-leve...

GPlates is an open‐source, cross‐platform plate tectonic geographic information system, enabling the interactive manipulation of plate‐tectonic reconstructions and the visualization of geo‐data through geological time. GPlates allows the building of topological plate models representing the mosaic of evolving plate boundary networks through time, u...

Full text: https://www.sciencedirect.com/science/article/pii/S1674987118301373 (open access) Abstract: Detailed global plate motion models that provide a continuous description of plate boundaries through time are an effective tool for exploring processes both at and below the Earth’s surface. A new generation of numerical models of mantle dyna...

The pyBacktrack software package allows the backtracking of the paleo-water depth of ocean drill sites, providing a framework for reconstructing the accumulation history of sediment components through time. The software incorporates the effects of decompaction of common marine lithologies and allows backtracking of sites on both oceanic and contine...

This poster was presented at the 2018 EGU conference. For more detail, please find the paper through the link: https://www.researchgate.net/publication/323702555_Palaeolatitudinal_distribution_of_lithologic_indicators_of_climate_in_a_palaeogeographic_framework

Traditional plate reconstruction methodologies do not allow for plate deformation to be considered. Here we present software to construct and visualize global tectonic reconstructions with deforming plates within the context of rigid plates. Both deforming and rigid plates are defined by continuously evolving polygons. The deforming regions are tes...

Whether the latitudinal distribution of climate-sensitive lithologies is stable through greenhouse and icehouse regimes remains unclear. Previous studies suggest that the palaeolatitudinal distribution of palaeoclimate indicators, including coals, evaporites, reefs and carbonates, has remained broadly similar since the Permian period, leading to th...

The recently released GPlates 2.0 software (www.gplates.org) provides a framework for building plate motion models including distributed extension and compression, driven by the motions of the surrounding rigid plate interiors, with constraints assimilated from well and seismic data. Here we present a regional deforming plate model for Australia an...

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 t...

Tectonic plates and plate boundaries migrate substantially through time and mantle plumes are generally accepted to be mobile within the convecting mantle, but it has been proposed that large low shear velocity provinces (LLSVPs) could have been fixed and rigid for as much as 540 million years (Myr). The hypotheses of fixed and rigid LLSVPs cannot...

The concentration of CO2 in the atmosphere is a key influence on Earth’s climate. Today, significant quantities of CO2 are emitted at continental rifts, suggesting that the spatial and temporal extent of rift systems may have influenced deep carbon fluxes and thus climate change throughout geological time. Here we test this hypothesis by conducting...

We introduce a set of basis functions for analysing magnetization in a plane layer, called Vector Cartesian Harmonics, that separate the part of the magnetization responsible for generating the external potential field from the part that generates no observable field. They are counterparts of similar functions defined on a sphere, Vector Spherical...

Whether the latitudinal distribution of climate-sensitive lithologies are stable through greenhouse and icehouse regimes remains unclear. Previous studies suggest that the paleolatitudinal distribution of paleoclimate indicators, including coals, evaporites, reefs and carbonates, have remained broadly similar since Permian times, leading to the con...

We evaluate the spatial and temporal evolution of Earth's long-wavelength surface dynamic topography since the Jurassic using a series of high-resolution global mantle convection models. These models are Earth-like in terms of convective vigour, thermal structure, surface heat-flux and the geographic distribution of heterogeneity. The models genera...

Volcanism of Late Cretaceous-Miocene age is more widespread across the Zealandia continent than previously recognized. New age and geochemical information from widely spaced northern Zealandia seafloor samples can be related to three volcanotectonic regimes: (1) age-progressive, hotspot-style, low-K, alkali-basalt-dominated volcanism in the Lord Ho...

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...

Extinct mid-ocean ridges record past plate boundary reorganizations, and identifying their locations is crucial to developing a better understanding of the drivers of plate tectonics and oceanic crustal accretion. Frequently, extinct ridges cannot be easily identified within existing geophysical datasets and there are many controversial examples th...

Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, hydrocarbon genesis, and to constrain and interpret the dynamic topography predicted by time-dependent global mantle convection models. Several global paleogeographic maps have been compiled and published but they are...