Large Sill Research Articles

Alkaline magmatism from the Lublin–Baltic area of Poland (SW slope of the East European Craton)—Manifestation of hitherto unrecognized early Carboniferous igneous province

AbstractOur study of boreholes, seismic survey and magnetic data from the region between the Baltic Basin and the Lublin Basin indicates the existence of numerous buried intrusions and effusive complexes, most of them unnoticed so far, together with a few igneous massifs. They are of alkaline character and developed in a time span of c. 348 to 338 Ma. Deep seismic data reveal the presence of large sills (up to 100 km long) within the crystalline basement and the overlying sedimentary cover, at depths of 7–14 km and 5.5–6.5 km, respectively. All these igneous rocks occur in the coherent region and constitute a hitherto unrecognized Lublin–Baltic Mississippian Igneous Province (>120,000 km2). Its denudation is evidenced by the Mississippian volcaniclastic formations of high thickness, developed in the adjacent basins. Igneous activity was triggered by thermal anomaly and/or mantle decompression caused by stress field reorganization, induced by the Variscan collision.

Using Lunar Granulites to Constrain Re‐Equilibration Timescales of Contact Thermal Metamorphism on the Moon

AbstractRocks of the lunar granulite suite are the product of high‐temperature metamorphism within the Moon's crust. However, to date, their formation conditions have few constraints. Here, we combine Ti‐in‐pyroxene element diffusion modeling and two‐pyroxene thermometry with thermal modeling of the lunar crust in order to assess potential heat sources that could generate granulite metamorphism within the lunar highland crust. For the samples investigated in this study, the pyroxene crystals experienced peak metamorphic temperatures between ∼1,027 and 1,091°C over timescales ranging from ∼153 years to ∼15.1 Kyrs. To best satisfy these temperature and timescale constraints, hot (∼2,300°C) impact melt sheets with thickness ranging from 350 m to 3.35 km—equating to impact crater diameters between ∼60 and 280 km—have the potential to heat the underlying anorthositic crust. Deep (>20 km) igneous bodies, such as the large (>10 km thick) sills observed by the GRAIL mission near the base of the lunar crust, also have the potential to generate the required peak metamorphic temperatures; however, the thermal equilibration timescales in this scenario are modeled to be much larger (>100 Kyrs) than was witnessed by the granulites investigated. Our modeling highlights that while lunar granulites are only a minor component within the Apollo and meteorite collection, they are likely an important and ubiquitous lithology within the lunar highland crust.

Nearly Three Centuries of Lava Flow Subsidence at Timanfaya, Lanzarote

AbstractThe 1730–1736 eruption on Lanzarote was one of the most significant volcanic eruptions to occur on the Canary Islands, with lavas covering over 200 km2. Globally, it is volumetrically the third largest known subaerial basaltic fissure eruption in the past 1,100 years. Here we use Sentinel‐1 and ENVISAT interferograms on both ascending and descending orbits to construct a time series of line‐of‐sight surface displacements and calculate linear vertical deformation rates. We resolve a constant subsidence rate of about 6 mm/yr associated with an area of ∼20 km2 within the central and western portion of the Timanfaya lava flows relative to the rest of the island. This is consistent over the 28‐year period (1992–2020) covered by the Sentinel‐1 and ENVISAT data when combined with the previously published European Remote‐Sensing Satellite data. Time series constructed using Sentinel‐1 short interval interferograms have previously been shown to suffer systematic biases and we find that by making longer period interferograms these biases can be mitigated (when compared against an averaged stack of 1‐year interferograms). Cooling‐driven contraction of an intrusion would require improbably large sill thickness to achieve the observed subsidence rates. Our observations are consistent with the cooling of lavas on the order of one hundred meters, twice as thick as previous estimates, which suggests overall lava volume for this eruption may have been underestimated. This is also evidence of the longest duration of lava flow subsidence ever imaged which indicates that these cumulative thick flows can continue to deform significantly even three centuries after emplacement.

The evolution of the Central Atlantic Magmatic Province (CAMP) plumbing system and its possible environmental effects during the Triassic-Jurassic transition: Insights from doleritic pipes of the Tindouf basin, SW Algeria

Exposed parts of the Central Atlantic Magmatic Province (CAMP) plumbing system, including huge doleritic sills and numerous dykes, are widespread in the northern flank of the Tindouf basin (Algeria). Doleritic pipes, that have never been studied so far, are spatially associated with these sills and dykes and thus supposed of CAMP origin. We present new field, petrographic and geochemical data on the pipe dolerites and other components of the CAMP plumbing system of the northern flank of the Tindouf basin. According to petrographic investigations, doleritic sills and dyke display homogeneous mafic petrographic features, typical of CAMP tholeiites, whereas doleritic pipes show more chemically evolved characteristics with granophyric texture containing an abundance of K-feldspar and quartz. Furthermore, we report for the first time the presence of abundant carbonatitic xenoliths in the pipe dolerites. Geochemically, all the investigated rocks are low-Ti tholeiites that can be subdivided into four groups, three of them correlate well with three (Intermediate, Upper and Recurrent units) of the four units defined in the High Atlas of Morocco, whereas the fourth group, represented by pipe dolerites, show geochemical features that have never been reported before. However, their tholeiitic nature, their association in the field at the same geographic location with CAMP sills, and their trace element patterns, all indicate that pipe dolerites are of CAMP origin, representing the evolved products of Recurrent magmas. Our study suggests that the small anticlines of the northern flank of the Tindouf basin that host doleritic pipes in its cores can be explained as forced folds above igneous intrusions. Finally, the high CO2 and sulfur contents of the pipe dolerites, combined with the emplacement of large sills within Upper Devonian organic-rich shales of Tindouf basin indicate an important emanation of CO2 and sulfuric gases that have contributed to climate change at the Triassic-Jurassic boundary.

Processes of sand entrainment and emplacement in sand injection complexes of the Viking Graben

Abstract The Balder Field reservoir sandstone has been interpreted as remobilized from a Mesozoic parent bed. This paper seeks to address the questions raised about this unusual origin. Research and broadly analogous processes are reviewed, leading to the proposal that the parent beds may have been fluidized by bedding-parallel retrogressive entrainment of Statfjord Formation sands by a connected larger source of overpressured fluids. These fluids are identified as most likely derived by lateral migration from the Viking Graben, initiated in response to early Eocene basin inversion related to North Atlantic rifting. The event probably involved breaching of the topseal in multiple places over a large section of the Utsira High. The geometry of large sills formed from small breach points and the internal differentiation seen may show that the sills inflated by lateral accretion from a medial active flowing zone of turbulent, transitional or laminar flowing suspension. It is suggested that sequence-stratigraphic and structural context should be considered as additional criteria to discriminate between depositional and intruded sands.

Rapid reduction of tidal amplitude due to form drag in a narrow channel

Reversing Falls is a large sill in a narrow section of the Saint John River on the northern coast of the Bay of Fundy, Canada. Reversing Falls limits tides from propagating farther up the river and impedes river water flowing seaward. This work aims to describe the physical processes that control flow over Reversing Falls by using output from a regional numerical model. We find form drag is more important than frictional drag for limiting the M2 tide propagation over Reversing Falls. Despite large tides and strong stratification suggestive of estuarine processes, the dynamics at Reversing Falls are dominated by a steady balance between drag and the surface pressure gradient, with the distinction that all terms in this river-like dynamical balance change sign on a semi-diurnal tidal cycle.

Subsurface characterization of Cenozoic igneous activity at Cerro Dragón area (Golfo San Jorge Basin, central Patagonia): Implications for basin evolution and hydrocarbon prospectivity

We use a 3D seismic dataset and wireline logs obtained during hydrocarbon exploration to describe the three-dimensional geometry and characteristics of mafic igneous rocks in the Cerro Dragón oilfield, Golfo San Jorge Basin, southern Argentina. Igneous intrusions occur within Upper Cretaceous and Paleocene sedimentary rocks at depths ranging from 2600 m to a ~200 m below of contemporaneous surface. Three distinctive types of shallow intrusions were recognized (layer-parallel, saucer-shaped, and transgressive sills). The largest sills are layer-parallel, some with estimated volumes up to 9,5 km3, whereas saucer-shaped sills and transgressive sills show widely variable intrusion geometries due to interaction with previous extensional tectonic structures and intrusion-related dikes. Sill intrusions were sourced either through vertical mafic dikes of NNW to NNE orientation, some up to 19 km in length and by sill-sill vertical connections. The presence of three imaged lava flows documents subaerial volcanic events coincident with the deposition of the Sarmiento Formation (late Eocene to early Miocene), whose trajectories were traced for 25–46 km of length.Cenozoic igneous intrusions produce both changes in the temperature history of the basin, and the remobilization of hosted hydrocarbon through the creation of supra-intrusion forced folds and new pathways generated during the igneous emplacement. Besides, sills and dikes act as barriers to both lateral and vertical fluid migration, and thus they need to be considered in petroleum prospect analysis.

Seismic characteristics and evolution of post-rift igneous complexes and hydrothermal vents in the Lingshui sag (Qiongdongnan basin), northwestern South China Sea

The study of morphology, distribution, and characteristics of igneous complexes has great significance to the understanding of magma plumbing processes, geodynamics, and tectonic evolution of continental margins. Previous studies concentrated partly on the magma-rich rifted basins, where the lateral magma transport mainly affects the igneous complexes' connection and distribution. However, due to seismic wave shielding effects of the large shallow magmatic bodies, the underlying igneous complexes and their corresponding magma plumbing systems in the magma-poor rifted margins are still in debate. In this study, 2D/3D seismic data and well data are utilized to describe the morphology, architecture, and spatial-temporal distribution of igneous complexes in the Lingshui sag of the Qiongdongnan basin, northwestern South China Sea margin. The identified igneous complexes include 98 intrusive sills and feeder dykes beneath some of the isolated sills. Twenty-six cone-shaped mounds that overlie intruded sills through internal disturbed conduits were also described. Drilled well samples and seismic expressions suggest that these mounds are hydrothermal vents. A uniform Bottom Mounds Horizon of these vents suggests that they probably formed at the same time. Constrained by biostratigraphic data and sedimentation rate of underlying and overlying sedimentary layers, the magma emplacement was dated to the middle Miocene (ca. 14.6 Ma). Most of the hydrothermal vents are distributed along the F2 fault zone and have direct linkage with the underlying sills, while the large sill complexes that are connected with limited vents are mainly present above the hyperextended continental crust, where the crust thins to 6–10 km. The sills intruded into different layers, from the lower Oligocene to the lower Miocene and the emplaced depth of sills is 1.2–6.3 km, whether or not they feed any vents above. Unlike most of the large volume and laterally linked sills found in the magma-rich rifted margins, the scattered distribution of sills at different levels indicates that dykes probably play an important role in magma transport, which might coexist with numerous polygonal or small faults and interference reflections. This work highlights the critical role of basin structures in controlling the distribution of post-rift igneous complexes in magma-poor margins, including thinned continental crust, sedimentary thickness, and faults.

Temporal and Topographic Source Effects on Tsunami Generation

AbstractWe present a systematic study of the influence on tsunami waves generated by the uplift of a rectangular plug, of the rise time of the deformation, and of its topographic details (e.g., the presence of a sill). We are motivated by the fact that most simulation codes use an instantaneous deformation of a flat ocean floor as an initial condition of the problem, although Hammack (1973, http://resolver.caltech.edu/CaltechAUTHORS:HAMjfm73) performed pioneering laboratory studies as well as analytical computations featuring variable rise times. Here, we consider three 2‐D source shapes, including a flat seafloor, a simple elevated piston, and additional trapezoidal sill on top of it, all with variable rise times, and simulate the resulting waves using the fully nonlinear smooth particle hydrodynamic model graphics processing unit smooth particle hydrodynamic. We validate our results against Hammack's (1973) laboratory measurements and analytical results. We find that a relatively large sill, with height and width of more than half of the local depth and width of the source, has a profound effect on the spatiotemporal structure of the generated free surface wavefield. Specifically, we show that the maximum water surface elevation over the source region is not always the same as the bottom displacement, as assumed in most tsunami propagation models. Next, we obtain simple scaling relationships to predict the maximum height of the generated tsunami over and outside the source, based on the geometry of the sill and the nondimensional bed rise time. Last, we show that inertial effects may lead to an initial free surface displacement over the generation region greater than the maximum vertical displacement of the displaced seabed.

Metamorphic mineral assemblages in fossils in the contact metamorphic rocks of the Portrush Sill, Northern Ireland

Ammonites and other metafossils have been identified in hornfelsed Jurassic clay from Portrush, Northern Ireland. Thermal metamorphism due to intrusion of a large sill complex produced zoned high temperature mineral assemblages due to reaction between the calcite and calcite/pyrite shells and the clay matrix. Modelling of hornfels compositions using Theriak – Domino gives a minimum temperature for metamorphism of ~600 °C at 200 bars. The metafossils comprise an inner wollastonite-rich core that also contains pyrrhotite and fayalite in the ammonites (zone 1), surrounded by iron-rich wollastonite, hedenbergite, titanite and feldspar (zone 2). The matrix in contact with the metafossil (zone 3) comprises magnesian hedenbergite, plagioclase and potassium feldspar and matrix distant from the fossils (zone 4) comprises augite, plagioclase, potassium feldspar, fayalite, ilmenite and quartz. These assemblages developed by metasomatic exchange of silica, sourced from the matrix with CaO sourced from the calcite shells. The metamorphic transformations, in particular reaction of calcite with silica-bearing fluids to form wollastonite and transformation of pyrite to pyrrhotite result in large volume changes which may have distorted the shape of the fossils, nevertheless original morphological features, particularly of the ammonites can be detected.

Rifting of western Laurentia at 1.38 Ga: The Hart River sills of Yukon, Canada

The Hart River sills are a set of mafic to intermediate intrusions that occur in northern Yukon, Canada. The largest sills are over 500 m thick and over 200 km long. New U-Pb dates of 1382.15 ± 0.39 Ma and 1382.14 ± 0.36 Ma were obtained via chemical abrasion thermal ionization mass spectrometry on zircon. Whole rock initial neodymium isotopic compositions of the Hart River sills are juvenile and have εNdi from +1.5 to +4.0. The primary mineralogy of the Hart River sills is predominated by clinopyroxene and plagioclase. Geochemical modeling indicates that the Hart River sills lie on a common liquid line of descent defined by a fractionating assemblage of plagioclase, clinopyroxene and minor olivine. The Hart River sills have rare earth element and high field strength abundances similar to normal mid-ocean ridge basalts (N-MORB) but are enriched in large ion lithophile elements. The Sm/Yb and Dy/Zr ratios indicate >8% partial melting of spinel-bearing mantle. During the emplacement of the Hart River sills, western Laurentia was juxtaposed with Australia and eastern Antarctica within the supercontinent Columbia. The degree of partial melting, similarity to N-MORB, and juvenile isotopic signature are consistent with an episode of rifting at 1.38 Ga. Coeval magmatism and intracontinental rift basins farther south on Laurentia provide additional evidence for rifting of supercontinent Columbia at 1.38 Ga.

Paleomagnetism of the Permian-Triassic intrusions from the Tunguska syncline and the Angara-Taseeva depression, Siberian Traps Large Igneous Province: Evidence of contrasting styles of magmatism

Based on the detailed paleomagnetic investigation, we distinguished different styles of intrusive magmatic activity in two regions of the Siberian Traps Large Igneous Province (LIP). The emplacement of intrusions in the Angara-Taseeva depression (the southern periphery of the Siberian Traps LIP) occurred as brief but intense bursts of magmatic activity that led to the emplacement of large and extensive sills. We argue that this pulsating style of intrusive magmatic activity is common for the margins of the Siberian Traps LIP. We also estimated the duration of the main magmatic events as <104–105years for the large sills and their area of manifestation (>200–250km in diameter and dozens of thousands km2 in square). On the contrary, in the central part of the Siberian Traps LIP (the Tunguska syncline) the intrusive magmatism was more or less continuous without intense peaks of magmatic activity. Furthermore, we obtained the first reliable magnetostratigraphic data from the volcanic section of the Tunguska syncline. Finally, we analyzed the available paleomagnetic and geochronological data from the Siberian platform and suggested the correlation scheme of the studied intrusive complexes with the volcanic sequences of the Siberian Traps LIP.

Igneous sills as a record of horizontal shortening: The San Rafael subvolcanic field, Utah

Igneous sills can facilitate significant lateral magma transport in the crust; therefore, it is important to constrain controls on their formation and propagation. Close spatial association between sills and dikes in layered (sedimentary) host rocks has led to a number of sill emplacement mechanisms that involve stress rotation related to layering; from horizontal extension and dike emplacement, to horizontal compression and sill emplacement. Here, we used field observations in the San Rafael subvolcanic field (Utah, USA), on the Colorado Plateau, supported by mechanical modeling, to show that layering is not the dominant control in all cases of sill formation. We found no compelling evidence of large sills fed by dikes; all observed cases showed that either dikes cut sills, or vice versa. Local sill contacts activate and follow host layer interfaces, but regionally, sills cut the stratigraphy at a low angle. The sills cut and are cut by reverse faults (1−3 m displacement) and related fractures that accommodate horizontal shortening. Minor sill networks resemble extension vein meshes and indicate that horizontal and inclined geometries were formed during coaxial horizontal shortening and vertical thickening. Although sills elsewhere may be related to mechanical layering during tectonic quiescence, our mechanical models show that the observed San Rafael subvolcanic field geometries are favored in the upper crust during mild horizontal shortening. We propose that sill geometry provides an indication of regional stress states during emplacement, and not all sill geometry is a response to bedding. Constraining sill geometry may therefore present a useful tool in plate-tectonic studies.

Generation of internal solitary waves over a large sill: From Knight Inlet to Luzon Strait

A fully nonlinear, nonhydrostatic numerical model is utilized to investigate the generation of Internal Solitary Waves (ISWs) upstream of the Knight Inlet sill. While an upstream hydraulic jump initiates the ISW generation and both hydraulic jump and upstream influence contribute to the generation, it is found that upstream influence is dominant and the hydraulic jump is not necessary for the ultimate generation of ISWs. Decreasing the tidal forcing or upstream sill width may render the flow subcritical (i.e., the hydraulic jump disappears) and ISWs can be generated by nonlinear steepening of long wave disturbances induced by upstream influence. Increasing the tidal forcing or upstream sill width may generate a hydraulic jump blocking strong upstream propagating disturbances. The jump subsequently becomes a turbulent bore and later disperses into a train of ISWs as the tide relaxes. Further increase in the tidal forcing may sweep the turbulent bore downstream and a train of ISWs is emitted upstream toward the end of waning tide. By reducing the stratification strength by 1 order of magnitude, the near-sill flow is in the transcritical regime and ISWs are resonantly generated over the lee side slope. Connections to the internal tide release mechanism at Luzon Strait and to the unsteady lee wave model are also discussed. The present work provides some more insights into the ISW generation process at Knight Inlet and the connection between the generation mechanism at Knight Inlet and that at Luzon Strait is identified.

Inelastic deformation during sill and laccolith emplacement: Insights from an analytic elastoplastic model

AbstractNumerous geological observations evidence that inelastic deformation occurs during sills and laccoliths emplacement. However, most models of sill and laccolith emplacement neglect inelastic processes by assuming purely elastic deformation of the host rock. This assumption has never been tested so that the role of inelastic deformation on the growth dynamics of magma intrusions remains poorly understood. In this paper, we introduce the first analytical model of shallow sill and laccolith emplacement that accounts for elastoplastic deformation of the host rock. It considers the intrusion's overburden as a thin elastic bending plate attached to an elastic‐perfectly plastic foundation. We find that, for geologically realistic values of the model parameters, the horizontal extent of the plastic zone lp is much smaller than the radius of the intrusion a. By modeling the quasi‐static growth of a sill, we find that the ratio lp/a decreases during propagation, as , with ΔP the magma overpressure. The model also shows that the extent of the plastic zone decreases with the intrusion's depth, while it increases if the host rock is weaker. Comparison between our elastoplastic model and existing purely elastic models shows that plasticity can have a significant effect on intrusion propagation dynamics, with, e.g., up to a doubling of the overpressure necessary for the sill to grow. Our results suggest that plasticity effects might be small for large sills but conversely that they might be substantial for early sill propagation.

Subsurface structure of a large basaltic maar volcano examined using geologically constrained potential field modelling, Lake Purrumbete Maar, Newer Volcanics Province, southeastern Australia

Lake Purrumbete Maar (LPM) is situated in the Late Cenozoic intraplate, basaltic Newer Volcanics Province, southeastern Australia. It is one of the largest maar volcanoes in the world with a near circular crater that is up to 2800m in diameter containing a 45m deep lake. Gellibrand Marl accidental lithics, which occurs to a maximum depth of 250m below LPM, represent the deepest excavated host rock unit present in the volcanic succession. Irregular clast shapes and peperitic textures observed in marl lithics suggest the host rock was poorly consolidated during the eruption. High-resolution lake- and land-based gravity and magnetic data were collected to conduct forward and inverse modelling of the subsurface architecture of the maar. This is done to test the assumption, based on lithics, that the diatreme is limited to 250m depth and identify the reasons behind LPM's large size. The collection of gravity data presented a unique challenge due to the nature of measuring small changes in gravitational forces (<1mGal) associated with the maar, on an inherently unstable water body. The magnetic anomaly over LPM shows several irregularly shaped high magnetic anomalies. Four 2.5-D forward models transecting LPM were constructed based on the observed potential field data. Five coalesced vents forming an undulating shallow bowl-shaped diatreme contained within the Gellibrand Marl (240m depth) were modelled to satisfy the observed magnetic response, while a large sill body at 350m depth is modelled to satisfy the observed gravity response. A second forward model, completed to satisfy the observed magnetic response, also includes coalesced shallow bowl-shaped diatremes within the Gellibrand Maar, which then taper down to become thin and steep sided and extend down to the basement (1,050m depth). Three-dimensional property and geometry inversions suggest the diatreme most likely extends to a greater depth than the initial maximum depth of 240m. This suggests the lithic-based maximum diatreme depth inferred by accidental lithics present in the volcanic successions is an underestimate.

Internal waves on the upstream side of a large sill of the Mascarene Ridge: a comprehensive view of their generation mechanisms and evolution

In this paper we aim to clarify the generation of Internal Solitary Waves (ISWs) at work to the east of the Mascarene Plateau (Indian Ocean) using Synthetic Aperture Radar (SAR) imagery and MITgcm fully nonlinear and nonhydrostatic simulations. Realistic representations of stratification and bathymetry are used with asymmetric tidal forcing (including the steady South Equatorial Current which is assumed barotropic in the model) along a 2D transect aligned with the propagation direction of the wave signatures identified in the SAR. The combined flow (i.e. steady and tidal currents) is subcritical with respect to first-mode Internal Waves (IWs), but supercritical with respect to higher wave modes. Different types of nonlinear wave trains with distinct origins (i.e. tidal phase and location) have been identified with the combined aid of model and SAR: (1) large-scale primary mode-1 ISWs evolve from the disintegration of a multimodal baroclinic structure that appears on the upstream side of the sill; (2) mode-2 ISW-like waves that evolve from this same baroclinic structure and are arrested over the sill before being released upstream at the change of flow condition; (3) a large mode-2 lee wave is generated downstream of the sill (i.e. on the west side), which is trapped there during maximum westward tidal flow and released upstream when the tide relaxes; and (4) mode-2 ISW-like waves whose length-scales are O (20km) appear some 50km upstream of the sill, after an Internal Tide (IT) beam scatters into the pycnocline, itself originating from critical topography on the leeward (i.e. westward) side of the sill. The underwater sill being investigated is in the mixed-tidal-lee wave regime, where the internal tide release mechanism, lee wave generation and IT beams can coexist. The large-scale mode-2 ISW-like waves that form far upstream from the sill are long-lived features and can be identified in the SAR due to associated short-scale mode-1 ISWs which propagate with the same phase speed, i.e. in resonance. This coupling is also seen in the model, and here it is argued that the formation of those mode-2 ISW-like waves appears to originate from the IT beam after it reflects from the sea surface and interacts with the pycnocline, a generation mechanism referred in the literature as “local generation of ISWs”. This IW generation process may be easily overlooked and could be at work in many more regions of the world than previously thought.

A large magmatic sill complex beneath the Toba caldera

An understanding of the formation of large magmatic reservoirs is a key issue for the evaluation of possible strong volcanic eruptions in the future. We estimated the size and level of maturity of one of the largest volcanic reservoirs, based on radial seismic anisotropy. We used ambient-noise seismic tomography below the Toba caldera (in northern Sumatra) to observe the anisotropy that we interpret as the expression of a fine-scale layering caused by the presence of many partially molten sills in the crust below 7 kilometers. This result demonstrates that the magmatic reservoirs of present (non-eroded) supervolcanoes can be formed as large sill complexes and supports the concept of the long-term incremental evolution of magma bodies that lead to the largest volcanic eruptions.

A Systematic Review of Driver Ingress and Egress Using Passenger Vehicles: Considerations for Designers

Identifying ingress and egress strategies is an important area of research in the automotive sector. Determining ingress and egress strategies can lead to safer vehicle design that reduce fall risk and improve comfort. In this systematic review, we examined studies related to ingress and egress in passenger vehicles after searching for various databases. We found 9 primary articles (of 608), all published in English. The results of the present research synthesis show that participants reported challenges with doorway height, sill height during ingress and egress, as well as will width during egress. There are also various ingress and egress strategies employed by drivers. However, ingress and egress strategies did not differ significantly by sample characteristics (i.e., age, height) or vehicle type. Roof height was not a factor of ingress and egress strategies although a large sill width may increase the risk of adverse events during egress. Future studies need to incorporate larger and more heterogeneous samples (i.e., healthy versus non-healthy, younger versus older adults) and relate participant characteristics (i.e., age, gender, height, weight) and the use of hands (along with force measurements) with ingress and egress strategies. Additionally, changes in vehicle design should be modelled with comfort ratings using metrics and loss functions to determine the optimal point between comfort and safety. This is the first review of the ingress and egress literature to summarize important findings and provide directions for future research.

Seismic imaging of ‘broken bridges’: linking seismic to outcrop-scale investigations of intrusive magma lobes

Three-dimensional seismic datasets have provided unrivalled insights into magma flow within sub-volcanic systems. One of the key revelations is that sills appear to be constructed of a series of discrete magma lobes that form during the emplacement of magma into host-rock. We focus on a large sill, within the Faroe–Shetland Basin, North Atlantic, that is well imaged on seismic data, and identify the presence of ‘broken bridges’ within the sill, developed between elongate magma lobes, and reveal for the first time in three dimensions the development of broken bridges. Critically, by relating the imaged structures to key outcrop-scale examples we confirm that bridge and broken-bridge structures are oriented perpendicular to the magma flow direction. This work thus demonstrates a key link that can be made between seismic-scale investigation of intrusions and sub-seismic (outcrop-scale) processes, highlighting the seemingly scale-invariant nature of the magmatic emplacement process.