Saucer-shaped sills Research Papers - Academia.edu (original) (raw)

2025

the hydrocarbon prospectivity assessment (Totterdell et al 2008). Most of the dredge sites were located in submarine canyons and scarps where steep slopes offer the best opportunity for sampling the sedimentary strata. Grab samples were taken at the base of a steep slope and provided additional information on lithologies present in the sedimentary succession above. A total of 199 rock samples were collected from 53 dredges, The recently completed marine reconnaissance survey of Australia’s southwestern margin was the first survey to collect rock samples from this under-explored deepwater area. Significant outcomes of the survey included: the recovery of nearly 200 rock samples from deep to ultra• deepwater sedimentary basins.

2025, Geosphere

The structure of upper crustal magma plumbing systems controls the distribution of volcanism and influences tectonic processes. However, delineating the structure and volume of plumbing systems is difficult because (1) active intrusion networks cannot be directly accessed; (2) field outcrops are commonly limited; and (3) geophysical data imaging the subsurface are restricted in areal extent and resolution. This has led to models involving the vertical transfer of magma via dikes, extending from a melt source to overlying reservoirs and eruption sites, being favored in the volcanic literature. However, while there is a wealth of evidence to support the occurrence of dike-dominated systems, we synthesize field-and seismic reflection-based observations and highlight that extensive lateral magma transport (as much as 4100 km) may occur within mafic sill complexes. Most of these mafic sill complexes occur in sedimentary basins (e.g., the Karoo Basin, South Africa), although some intrude crystalline continental crust (e.g., the Yilgarn craton, Australia), and consist of interconnected sills and inclined sheets. Sill complex emplacement is largely controlled by host-rock lithology and structure and the state of stress. We argue that plumbing systems need not be dominated by dikes and that magma can be transported within widespread sill complexes, promoting the development of volcanoes that do not overlie the melt source. However, the extent to which active volcanic systems and rifted margins are underlain by sill complexes remains poorly constrained, despite important implications for elucidating magmatic processes, melt volumes, and melt sources. GEOSPHERE; v. 12, no. 3

2024

3D and 2D seismic data from the Northern Carnarvon Basin provide an opportunity to analyze the structural evolution of the basin. This is a rift-dominated basin, formed by five phases of extension (Pre-Top Permian, Top Permian, Base Jurassic, Middle Jurassic, and Late Jurassic Extension, versus only the four previously identified) and the Base Cretaceous inversion across the Northwest Shelf of Australia. The first deformation by listric fault initiation in the basin resulted in a newly defined Pre-Top Permian Extension, generating the Exmouth, Dampier, Barrow and Beagle Sub-basins. The magnitude of the rift phases remained approximately the same during the earliest three phases of extensions, but increased during the Middle and Late Jurassic Extension. Additionally, four detachment surfaces are identified whereas only two were determined previously. Moreover, a simple shear "Wernicke" model best defines the style of deformation during the five phases of extension in the Northern Carnarvon Basin, with delamination under the region between the WNW edge of the Exmouth Plateau and the Gascoynee Abyssal Plain, opposing the symmetrical McKenzie Model previously assigned bu Mutter et al. Lastly, the amount of extension during the rift phases and the amount of shortening during the inversion are determined to be highly variable from the results of restorations throughout the basin. A transition from the rift-dominated margin to the passive margin is marked by the end of the Late Jurassic Extension. Results of this research are applicable to hydrocarbon exploration because this study is conducted across the entire Northwest Shelf of Australia, showing more precise relationships between structural features such as sub-basins, plateaus, shelves, platforms, synclines, arches, troughs, abyssal plains, depocenter evolution, faults, folds, harpoon structures etc. rather than limited to a smaller scale. Output of 3D surfaces with the modelled fault families in a structural v TABLE OF CONTENTS

2024, Geology

Shallow-level sill emplacement can uplift Earth's surface via forced folding, providing insight into the location and size of potential volcanic eruptions. Linking the structure and dynamics of ground deformation to sill intrusion is thus critical in volcanic hazard assessment. This is challenging, however, because (1) active intrusions cannot be directly observed, meaning that we rely on transient host-rock deformation patterns to model their structure; and (2) where ancient sill-fold structure can be observed, magmatism and deformation has long since ceased. To address this problem, we combine structural and dynamic analyses of the Alu dome, Ethiopia, a 3.5-km-long, 346-m-high, elliptical dome of outward-dipping, tilted lava flows cross-cut by a series of normal faults. Vents distributed around Alu feed lava flows of different ages that radiate out from or deflect around its periphery. These observations, coupled with the absence of bounding faults or a central vent, imply that Alu is not a horst or a volcano, as previously thought, but is instead a forced fold. Interferometric synthetic aperture radar data captured a dynamic growth phase of Alu during a nearby eruption in A.D. 2008, with periods of uplift and subsidence previously attributed to intrusion of a tabular sill at 1 km depth. To localize volcanism beyond its periphery, we contend that Alu is the first forced fold to be recognized to be developing above an incrementally emplaced saucershaped sill, as opposed to a tabular sill or laccolith.

2024, International Conference and Exhibition, Melbourne, Australia 13-16 September 2015

Phase 1 of the WestraliaSPAN 2D regional program extended across all basins of Australia's North West Shelf (Carnarvon/ Roebuck/ Browse/ Bonaparte basins) and Arafura regions, although it was restricted to Australian waters. In 2014, an additional 2500 km of new data was collected during Phase 2, which extends the survey to Timor and neighbouring islands. Phase 2 of the survey was designed with long offset and record length (18 sec) acquisition parameters to image the deep crustal and sub crustal architecture and depositional systems across this complex margin. The regional program provides unique, state-of-the-art depth imaging of the deep structure of the Westralian Superbasin, lower crust and Moho. The survey now has multiple transects across the Bonaparte Basin which cross the transition from unextended continental, through hyperextended, transitional and oceanic crust and now includes the Timor accretion complex. An integrated geological and geophysical interpretation encompassing available well, seismic and potential field data was undertaken. Gravity models were developed to aid in seismic depth conversion and the structural interpretation of the deep crust and Moho. A comprehensive model for basin formation provides the context for regional correlation of tectonostratigraphic packages throughout these linked basin systems, highlighting pre-Jurassic basins and their structural controls. Combined seismic velocity and gravity models along the newly acquired Timor data also suggest that there may be essentially no continental crust remaining beneath the Westralian Superbasin and Timor accretion complex. When combined with Phase 1 of the WestraliaSPAN 2D survey, the Phase 2 data provide insight into the distribution of volcanic and originally non-volcanic-hyperextended crust along the entire length of the North West Shelf. While the North West Shelf, Browse and Bonaparte basins are proven and established hydrocarbon provinces, a future step-change in exploration concepts is required, which involves an integrated, margin-scale understanding of these basin systems and their potential resources. Collectively, the new dataset and interpretation will aid explorers in understanding the nature and distribution of key petroleum systems elements (reservoir/source/seal) and processes (heat-flow, timing of source maturity, expulsion, migration and entrapment).

2024, EarthArXiv (California Digital Library)

The geomorphology and sediment systems of volcanic areas can be influenced by uplift (forced folding) related to subsurface migration and accumulation of magma. Seismic geomorphological analysis presents a unique tool to study how surface morphology and subsurface magma dynamics relate, given seismic reflection data can image buried landscapes and underlying intrusions in 3D at resolutions of only a few metres-to-decametres. However, differential compaction of the sedimentary sequence above incompressible igneous intrusions during burial modifies palaeosurface morphology. Here we use 3D seismic reflection data from offshore NW Australia to explore how the stratigraphic record of igneous intrusion and associated ground deformation can be unravelled. We focus on a forced fold that formed in the Early Cretaceous to accommodate intrusion of magma, but which was later amplified by burial-related differential compaction of the host sedimentary sequence. We show how: (1) marine channels and clinoforms may be deflected by syn-depositional intrusion-induced forced folds; and (2) differential compaction can locally change clinoform depth post-deposition, potentially leading to erroneous interpretation of shoreline trajectories. Our results demonstrate seismic geomorphological analysis can help us better understand how magma emplacement translates into ground deformation, and how this shapes the landform of volcanic regions.

2024, EGUGA

Almost all eruptions are supplied with magma through dykes or inclined sheets (cone sheets). The dykes/sheets, in turn, are injected from a source which is normally either a shallow magma chamber or a deep-seated reservoir. During a volcanic unrest period with dyke injection, one main aim is to forecast the likely propagation path of the dyke and, in particular, the probability of the dyke reaching the surface to erupt. The propagation path of a dyke injected from a chamber/reservoir during unrest is partly determined from seismic data and partly from geodetic surface data, in particular InSAR and GPS data, using mostly dislocation models that assume the volcanic zone to be elastic half spaces of uniform mechanical properties. By contrast, field observations of volcanoes (active and extinct) show that they are composed of layers whose mechanical properties vary widely. In particular, Young's modulus or stiffness of layers and contacts in a typical active volcanic zone may vary by 2-3 orders of a magnitude. How mechanical layering affects dyke-propagation paths is best determined by detailed field studies of actual dykes in well-exposed sections composed of widely different rock layers. Such sections, with many dykes and a great variety in the mechanical properties of the layers and contacts, are provided by the caldera walls of Santorini, a stratovolcano located in the Aegean Sea, Greece. The volcano is a part of the active Hellenic South Aegean Volcanic arc, formed by the subduction and rapid rollback of the African plate beneath the Aegean microplate. This study focuses on quantifying dyke propagation paths, combining field data from Santorini with numerical models. To do this we have mapped a dyke swarm exposed in the northern caldera wall. We measured the attitude and thickness of 91 dykes as well as features such as dyke segmentation, arrested dike tips, associated faults and other discontinuities. In this study we seek to understand the role of mechanical anisotropy in influencing dyke propagation paths, including dyke arrest. The finite-element software COMSOL Multiphysics is used to model dyke-propagation paths as seen in the field. In the model runs we use different mechanical properties of the layers, vary the magmatic overpressure (driving pressure) as well as the external, tectonic loading. The calculated crustal stresses, in particular the trajectories (orientations) of the maximum compressive principal stress, are then used to forecast the likely dyke-propagation paths. The numerical results are then compared with the observed dyke paths. We also study the effects of normal faults, of which there are several in the sections, on dyke paths. Some dykes follow steep normal faults along parts of the dyke paths, but then leave the fault at shallower crustal depths to resume their normal path. Other dykes are seen to be arrested at discontinuities and contacts between mechanically dissimilar layers. Layering, contacts, and local stresses apparently largely control dyke paths.

2023

The geometries of planar igneous intrusions such as dykes, sills and inclined sheets have often been used to delineate emplacement mechanisms, magma flow pathways, and melt source locations in crustal magma plumbing systems. It is known that dykes and sills do not always propagate with uniform margins but instead break down into finger-like and/or lobate segments. The morphology and propagation mechanism of these segments and how they connect are still debated and mostly explained by brittle-elastic instabilities, where tensile brittle fracture leads to the formation of segment connectors such as steps and broken bridges. However, non-brittle emplacement mechanisms such as ductile flow processes and heat-induced fluidisation also show the development of such segments. Recent studies have also suggested that magma cooling and solidification can contribute to formation of segments.

2023, Geology

Analysis of the volcanic edifice and its geological context was accomplished by interpreting different exclusive datasets of seismic surveys, that include (Fig. 1): 1) 2D Two-Way Time (TWT) Post-Stack Time Migrated, acquired by TGS (2000-2002), and 2) 3D Pre-Stack Depth Migrated (PSDM) seismic acquired by CGG Veritas (2010), covering an area of 2096 km 2 , using 10 streamers each 8100 m long, a spacing of 100 m, and recording frequencies within the range of 30-200 Hz. At the target depth, this allows a vertical seismic resolution of around 40-60 m , from a range of acoustic frequencies of 20-30 Hz. Details on dredge results at the Fontanelas volcano, including lithological description, rock properties and whole-rock geochemistry data, are based in the reports of Miranda (2010). METHODS Analysis of the architectural elements of the volcanic edifice was performed following seismic geomorphology and seismic volcano-stratigraphy criteria (e.g., Bischoff et al., 2021).

2023

2023, Marine and Petroleum Geology

Hydrothermal vents are structures that occur close to volcanically active areas. Their occurrence can have considerable impacts on the evaluation of the oil reserves of a basin. In the Campos Basin, eastern Brazilian continental margin, no hydrothermal vents have been previously recognized and related with magmatic events on seismic sections. This work aims to map the hydrothemal vents, ducts and associated intrusive bodies observed in the rifte section. With the use of 2D seismic data and a well with lithologic information, the occurrence of ten hydrothermal vents and seven ducts were mapped and the interval with volcanic intrusive rocks was characterized. The identification of intrusive rocks in seismic data is given by reflectors with high amplitude and disk or half-moon geometry with abrupt endings. The vent geometries shows dome and eye-shaped types and the ducts are fault-related, downward-tapering cone type. This study highlights new geological elements that can influence the petroleum systems of the Campos Basin, such as the identification of hydrothermal vents in seismic sections and the correlation with regional tectono-magmatic events.

2023, ASEG extended abstracts

Basin and petroleum system modelling of the Exmouth Sub-basin Schenk et al.

2023, ASEG extended abstracts

2023, Frontiers in Earth Science

In this article, the basic principles of the scaling procedure are first reviewed by a presentation of scale factors. Then, taking an idealized example of a brittle volcanic cone intruded by a viscous magma, the way to choose appropriate analog materials for both the brittle and ductile parts of the cone is explained by the use of model ratios. Lines of similarity are described to show that an experiment simulates a range of physical processes instead of a unique natural case. The pi theorem is presented as an alternative scaling procedure and discussed through the same idealized example to make the comparison with the model ratio procedure. The appropriateness of the use of gelatin as analog material for simulating dyke formation is investigated. Finally, the scaling of some particular experiments such as pyroclastic flows or volcanic explosions is briefly presented to show the diversity of scaling procedures in volcanology.

2023

Igneous sills are common features in tectonically active regions, acting as nascent magma storage systems, or feeding eruptions at large lateral distances from the magma source. Sills reaching a critical radius, rc, relative to their initial depth, H, interact with Earth’s surface, leading to mild discordant growth at angle [theta] typically <10[deg] forming saucer-shaped sills; commonly rc>3H for natural sills. Analogue and numerical models for sills produce saucer shapes where [theta] >10[deg] and rc

2023, Nature communications

Magmatic intrusions and volcanic eruptions are intimately related phenomena. Shallow magma intrusion builds subsurface reservoirs that are drained by volcanic eruptions. Thus, the long-held view is that intrusions must precede and feed eruptions. Here we show that explosive eruptions can also cause magma intrusion. We provide an account of a rapidly emplaced laccolith during the 2011 rhyolite eruption of Cordón Caulle, Chile. Remote sensing indicates that an intrusion began after eruption onset and caused severe (>200 m) uplift over 1 month. Digital terrain models resolve a laccolith-shaped body ∼0.8 km(3). Deformation and conduit flow models indicate laccolith depths of only ∼20-200 m and overpressures (∼1-10 MPa) that likely stemmed from conduit blockage. Our results show that explosive eruptions may rapidly force significant quantities of magma in the crust to build laccoliths. These iconic intrusions can thus be interpreted as eruptive features that pose unique and previously...

2023, Journal of Structural Geology

2023, Nature communications

2023, ASEG Extended Abstracts

Basin and petroleum system modelling of the Exmouth Sub-basin Schenk et al.

2023, ASEG Extended Abstracts

Increased hydrocarbon exploration along rifted continental margins indicates the need of a better understanding of the impact and influence of igneous rocks on hydrocarbon systems as they are often present in these tectonic settings. The southern Australian margin contains several petroliferous sedimentary basins which contain Cretaceous-Cenozoic igneous rocks and is therefore an ideal study area to investigate both the positive and negative effects on hydrocarbon systems. In particular, the Kipper Field in the offshore Gippsland Basin forms an excellent example of a volcanic play, as it holds a 328 m gas column and 14 m oil leg sealed by a >100 m thick basaltic lava flow juxtaposed against a sealing fault. The basin also contains a number of cross-cutting and layer-parallel type intrusions, although their impact on the petroleum system is as-yet unclear. Seismic interpretation techniques such as spectral decomposition and opacity rendering combined with electrical log signatures allowed us to identify the lava flow and intrusions down dip from the fault. Whether this fault has acted as a conduit for the magma responsible for the lava flow is still unclear. Future work will aim to further delineate and constrain flow paths of the intrusive and extrusive rocks near the Kipper Field and their influence on the Kipper play. This study highlights the importance of volcanic rocks in hydrocarbon basins and the possible effect they can have on hydrocarbon systems.

2023

2023, ASEG Extended Abstracts

Finder Exploration and its joint venturer Carnarvon Petroleum commissioned Fugro Airborne Surveys to acquire and interpret 21,622 line kilometres of airborne magnetic data over Petroleum Exploration Permits WA-436-P and WA-438-P in the Bedout Sub-basin, offshore Canning Basin within the Northwest Shelf, Western Australia. These data were acquired to augment the existing sparse 2D seismic data in the study area. As part of the ongoing exploration effort, this new aeromagnetic data and interpretation has added to the understanding of the study area by identifying a possible additional hydrocarbon source kitchen and improving the tectono-structural understanding of the Bedout Sub-basin.

2023, Bulletin of Volcanology

Prior to and during eruptions, magma is stored and transported within volcanic and igneous plumbing systems (VIPS) that comprise a network of magma reservoirs and sheet intrusions. The study of these VIPS requires the combination of knowledge from the fields of igneous petrology, geochemistry, thermodynamic modelling, structural geology, volcano geodesy, and geophysics, which express the physical, chemical, and thermal complexity of the processes involved, and how these processes change spatially and temporally. In this contribution, we review the development of the discipline of plumbing system studies in the past two decades considering three angles: (1) the conceptual models of VIPS and paradigm changes, (2) methodological advances, and (3) the diversity of the scientific community involved in VIPS research. We also discuss future opportunities and challenges related to these three topics.

2023, The APPEA Journal

The Northern Carnarvon Basin (NCB) hosts an extensive record of Jurassic–Cretaceous rift-related igneous activity, manifested by a >45 000 km2 intrusive complex and series of volcanic centres constrained by seismic mapping. However, there are relatively few well penetrations of these igneous rocks (<1% of ~1500 exploration wells) in comparison to other basins that witness extensive magmatism, and thus, their lithological and petrophysical characteristics are poorly understood. Here, we describe the properties of igneous rocks encountered in nine petroleum exploration wells and scientific boreholes in the NCB and evaluate their impacts on exploration and development issues. Igneous rocks in the NCB are characterised by pervasive alteration, with ramifications for seismic imaging and drilling. For example, low acoustic velocities in mafic lavas altered to clays in Toro-1 were mistaken for overpressure, whilst intrusive rocks in Palta-1 were initially unrecorded and only recognis...

2023, International Conference and Exhibition, Melbourne, Australia 13-16 September 2015

2023, SEG Technical Program Expanded Abstracts 2015

This study aims to combine a novel global interpretation method, using a relative geological time model and spectral decomposition imaging techniques, into a powerful workflow capable of extracting from seismic data very fine geomorphological features. The workflow was applied to a public domain 3D marine seismic data set covering the Exmouth Sub-basin in Northwestern Australia. The analysis at a sub-seismic scale of horizons stacks allowed the interpretation of complex geo-bodies, which would have remained undetected with classical methods.

2022

In this study, the development of structural elements and the relationship between these elements and dikes emplacements investigated by the field surveys and analysis of satellite images of the East Dasht-e Bayaz Fault Zone. In this area NNW-SSE (T2) and NW-SE trending dikes are which follow the fractures of the region. We measured geometric characters of dikes (such as thickness, attitude, dip, …) also major and minor faults or related fractures recognized. The Riedel fractures (R), which depend on the major faults, with NE-SW trending and with sinistral components have cut and displaced the NW-SE dikes. There are two folds traces in the region, NE-SW (C2) which is perpendicular to T2 fractures and the syncline Hatam Abad (with NE-SW fold trace) which is perpendicular to NW-SE dikes. On the other hand, the change of main stress trend (σ1) from NW-SE to NE-SW proves the existence of rotation in fault parallel simple shear.

2022, Acta Geologica Sinica - English Edition

Like all swarming behavior in Nature, the selforganization expressed by the emergence of a natural spacing among a swarm's members should be considered its most fundamental characteristic, and grasping the mechanics governing the swarming behavior is synonymous with grasping the drivers that lead to the emergent spacing. This presentation will tell the story of a recent research effort aimed at finding the ingredients required for swarming behavior to occur in systems of fluid-driven cracks such as dykes and hydraulic fractures. At first one might expect relatively analogous behavior between swarms of dykes and swarms of man-made hydraulic fractures. After all, the mathematical models used to describe these processes are strikingly similar (e.g. Lister, 1990 compared with e.g. Khristianovic and Zheltov, 1955). However, the typical observed behaviors of the natural and manmade systems are substantially different. One the one hand, hundreds to thousands of dykes often cluster together as swarms, possibly with many dykes growing at the same time so that the number of dykes exceeds the number of discrete magma pulses. On the other hand hydraulic fractures tend to localize to one or two dominant strands and, in the absence of mechanical isolation of already-fractured regions, subsequent pulses of injection are not typically found to produce spatially-distributed swarms-like collections of hydraulic fractures.

2022

2022, Frontiers in Earth Science

2022, Journal of Geophysical Research: Solid Earth

Elastic deformations of host rocks during the emplacement within the Earth's crust of magmatic intrusions, such as laccoliths and lopoliths, are analyzed. The present analysis is built upon semianalytic elastic solutions for a pressurized horizontal crack buried between an overburden and a semi-infinite base. The current work improves upon recent analyses by including several important features inherent to the development of laccoliths and lopoliths. First, both elongated intrusions (plane strain case) and circular intrusions (axisymmetric case) are described by the current models. Second, the effect of the difference in elastic moduli between the overburden and the substrate is considered. This difference in elastic moduli is characterized by one of the Dundurs parameters. Third, the stress intensity factor at the tip of the crack is assumed to be zero. Thus the stresses are finite, and the obtained laccolithic shapes are doubly hinged with horizontal slopes at the peripheries, as observed in the field. Fourth, unlike plate bending models, which are commonly used for major laccoliths, the current models describe a full range of ratios of intrusion width to overburden thickness. Numerical results are obtained for different combinations of the geometrical parameters, the material contrast and the driving pressure distributions. Graphs of these results confirm the plate bending model for large laccoliths, support Gilbert's concept pertaining to small laccoliths, permit the prediction of the sill-laccolith transition, allow the analysis of the asymmetry in the vertical displacements above and below the intrusion, and lead to a possible mechanism of deep lopoliths emplacements. Some of the obtained results are compared to the available field data from the Henry Mountains. has a diameter of-10 km and is on the eastern flank of Mount 13,781

2022

Craters of elevation are uplifts with apical depressions that are caused by shallow magma intrusion. Forced folds are dome-like folds caused by magma intrusion that also have apical extensional structures. They are the same feature described from the different viewpoints of the volcanologist and the structural geologist. While working on such features in the Chaîne des Puys (Central France), and Ethiopia we have been searching for other examples in the world. This is our most up to date review of such phenomena taken from a global search in the world of volcanology where some stunning examples are seen in the landscape, and in outcrop. We also show such features from tectonics data and literature, where such features are superbly displayed in seismic data. We take three examples, the Puy de Gouttes, in the Chaîne des Puys, the Montana Encantada in Lanzarote, which we have mapped in the field, and the Diamond Craters National Monument in Oregon to show the different structures and possible evolutionary trends that such features can follow. We use the observations to integrate the possible eruptive, deformational and structural events that can combine in a forced fold to create the surface features observed at such craters of elevation. The hazard implications of the growth and destruction of such features are assessed.

2022, Journal of Volcanology and Geothermal Research

Geodetic modelling has become an established procedure to interpret the dynamics of active volcanic plumbing systems. Most established geodetic models implemented for inverting geodetic data share similar physical assumptions: (1) the Earth's crust is modelled as an infinite, homogeneous elastic half-space with a flat surface, (2) there is no anisotropic horizontal stress to simulate tectonic stresses, (3) the source boundary conditions are kinematic, i.e., they account for an instantaneous inflation or deflation of the source. Field and geophysical observations, however, provide evidence that significant inelastic shear deformation of the host rock can accommodate the propagation of dykes and sills. We show that inelastic processes accommodating the emplacement of dykes in the brittle crust have large implications for dyke-induced surface deformation patterns.

2022, Journal of Geophysical Research: Solid Earth

 The Cerro Bayo cryptodome grew progressively through continuous intrusion of crystal-rich trachyandesitic magma into the Chachahuén volcano.  Strain during intrusion growth produced extensive brecciation of the intrusion rim.  Viscous stalling of the emplaced magma diverted subsequently intruding magma into two lobes that pierced through the rim of the intrusion.

2022, ASEG Extended Abstracts

Basin and petroleum system modelling of the Exmouth Sub-basin Schenk et al.

2022, ASEG Extended Abstracts

2022, Mediterranean Journal of Humanities

Sillyon, an important settlement in the region of Pamphylia, displays an urban development as per topography; its water supply system constitutes the scope of the present study. The quintessential element of life, as a fundamental supply and different from other natural resources, water has been exploited for political and social targets, apart from its economic value in the past and today. Based on this opinion, the water sources and structures of ancient Sillyon have been explored with an interdisciplinary approach within the frame of archaeology and hydrological engineering. The water structures attested in the city have been studied thoroughly and their approximate capacities have been calculated. Precipitation, temperature and humidity data of the city have been scrutinized and flooding occasions of the basin have been evaluated. Based on these data, various proposals have been made regarding the urbanistic fabric and city population of the city. It has been understood that the water structures at Sillyon were utilized in accordance with the continuing urban tradition, which had become traditional through the ages, that the morphological fabric of the territory was followed in the basis of the water supply system, and that a functional system was preferred rather than a regular planning. Nevertheless, an implementation not attested in other cities emerges at Sillyon, as that most of the water demand of the city was supplied from sources flowing at a certain altitude. It has been noted that these sources dictated the locations and volumes of important facilities such as Roman Bath, Nymphaeum A, Aquaeductus and Ottoman Fountain.

2022, Exploration Geophysics

A large portion of the southern Joseph Bonaparte Gulf area, northwestern Australia, was originally underlain by extensive contiguous Proterozoic sills and volcanic rocks. Subsequent extension and basin formation in this area during the Palaeozoic fractured this horizontal basic magnetic sheet. Evidence of this fracture patten and the extensional movements are obvious in images of the magnetic field over the basin. A series of transfer fault accommodation zones trending at 035 degrees and an associated series of perpendicular normal faults have been mapped. Onshore geology, gravity and seismic data support the transfer fault model. An underexplored graben, 75 kilometres long and 50 kilometres wide, which formed as a result of the extension process, has been mapped on the western edge of the Joseph Bonaparte Gulf adjacent to the Proterozoic Kimberley Basin.

2022, Journal of Sedimentary Environments

Historically, volcanic basins have been avoided by oil and gas companies for hydrocarbon exploration, due to high rates of unsuccessful cases, mainly when magmatic suites were unexpected. Furthermore, igneous rocks have always been considered harmful to petroleum systems. However, in the past two decades, researches regarding these systems in volcanic basins have shown a number of positive effects, as increasing permeability of tight rocks, and generation of traps. This work aims to investigate the occurrence and impacts of igneous intrusions on sedimentary basins regarding the reservoir and trap elements. For that, we use eight 2D seismic lines and five wells within the Papa-Terra field, southern Campos Basin, Brazil. Applying seismic stratigraphy, nineteen sills were identified, most of them have saucer-shaped geometries, but they are also planar. We have identified some possible joint connections in the NW sill complex, as well as a possible feeder dyke. Five sills are located ri...

2022, keckgeology.org

Figure 4. (Above) Model produced for the South dike for a profile at 695.7 km UTM-easting and 4054.3 km UTM-northing. (i) Theoretical anomaly overlain on the measured anomaly. (ii) Model of the section of the dike producing the... more

2022, Journal of Geophysical Research

The use of elastic plate theory to model the emplacement of laccoliths and large mafic sills has been debated for nearly 40 years. These intrusions typically attain a horizontal width that is large relative to the emplacement depth. Provided that large-scale plasticity and/or heterogeneity is not observed in the overlying host rock, it should then be valid to approximate its deformation based on analysis of a thin elastic plate with effective properties that are the consequence of interaction among heterogeneities that are small relative to the size of the intrusion. But the predictions that are usually cited from elastic plate theory are characterized by bell-shaped geometry, in contrast to the flat-topped, steep-sided geometry typical of many laccoliths or the nearly uniform thickness typical of large mafic sills. This fact has motivated several alternate explanations of laccolith and large mafic sill emplacement. Nonetheless, elastic plate theory should be revisited in light of the fact that previous elastic plate-based predictions have, in general, not taken into account an appropriate fracture propagation condition, fluid flow in the growing intrusion, and, importantly, the influence of the weight of the magma on intrusion growth. We present a model for the growth of circular intrusions that accounts for all of these factors. The model predicts the appropriate geometry for both laccoliths and large mafic sills. The predicted thickness to length relationships are also consistent with field data. Hence, while it may sometimes be appropriate, there is, in general, no fundamental need to appeal to large-scale rock plasticity in order to explain observed intrusion geometries, and it may, in fact, be appropriate to understand the growth of laccoliths and large sills in light of a single underlying mechanical model.

2022, ASEG Extended Abstracts

2022, Earth and Planetary Science Letters

Magmatic intrusions and fluidized injected sands represent the two main types of sheet intrusions in the Earth's crust. In this paper we show that both intrusion types often display a saucer-like geometry, as revealed by 3D seismic imaging and field observations. Saucer-shaped intrusions are fairly common in sedimentary basins, as for example offshore in the Norwegian and North Sea basins and onshore in the Karoo Basin of South Africa. The formation of the saucer geometry is controlled by the lowviscosity of the injected fluid and by the interaction between a growing shallow hydraulic fracture and overburden deformations. Statistics gathered from observations and modelling show a linear relationship between the depth of emplacement and the size of the saucer-shaped intrusions. We anticipate future cross-disciplinary studies aiming to discover other occurrences of saucer-shaped intrusions and to identify the physical processes controlling the development of this fundamental geometry.

2022

Magnetic anomalies in the southwestern zone of the Iberian Peninsula are characterized by a large N-S dipole elongated in E-W direction. The most intense anomaly values are related to the outcropping sienites of the Monchique Alkaline Complex, intruding the metapelitic host rock of the South Portuguese Zone. Total field magnetic intensity data have been acquired along a N-S profile (Portimão-Odemira) across the dipole. Moreover, magnetic susceptibility of the outcropping Monchique rocks has been measured (0.029 SI). Simultaneous modeling of aeromagnetic and field magnetic data may constrain the geometry and depth extension of the Monchique Alkaline Complex. It has roughly lenticular and asymmetrical section extending in depth towards the north. The maximum thickness of more than 3 km is reached in the southern side of the profile where the intermediate rocks outcrop.

2022, Bulletin of Volcanology

Tables S1-S2 provide details of field measurements, remote-sensing analyses, and eruptive center alignments. Supplementary methods and Figs. S1-S2 and provide a description of the criteria for calculating eruptive center alignments and a... more