159 results found
Magee C, Ernst RE, Muirhead J, et al., 2019, Magma Transport Pathways in Large Igneous Provinces: Lessons from Combining Field Observations and Seismic Reflection Data, Dyke Swarms of the World: A Modern Perspective, Publisher: Springer, Pages: 45-85, ISBN: 9789811316654
Large Igneous Province (LIP) formation involves the generation, intrusion, and extrusion of significant volumes (typically > 1 Mkm3) of mainly mafic magma and is commonly associated with episodes of mantle plume activity and major plate reconfiguration. Within LIPs, magma transport through Earth’s crust over significant vertical (up to tens of kilometres) and lateral (up to thousands of kilometres) distances is facilitated by dyke swarms and sill-complexes. Unravelling how these dyke swarms and sill-complexes develop is critical to: (i) evaluating the spatial and temporal distribution of contemporaneous volcanism and hydrothermal venting, which can drive climate change; (ii) determining melt source regions and volume estimates, which shed light on the mantle processes driving LIP formation; and (iii) assessing the location and form of associated economic ore deposits. Here, we review how seismic reflection data can be used to study the structure and emplacement of sill-complexes and dyke swarms. We particularly show that seismic reflection data can reveal: (i) the connectivity of and magma flow pathways within extensive sill-complexes; (ii) how sill-complexes are spatially accommodated; (iii) changes in the vertical structure of dyke swarms; and (iv) how dyke-induced normal faults and pit chain craters can be used to locate sub-vertical dykes offshore.
Steventon MJ, Jackson CA-L, Hodgson DM, et al., Strain analysis of a seismically-imaged mass-transport complex (MTC), offshore Uruguay, Basin Research, ISSN: 0950-091X
Jackson CA-L, Elliott GM, Royce-Rogers E, et al., Salt thickness and composition influence rift structural style, northern North Sea, offshore Norway, Basin Research, ISSN: 0950-091X
Jackson C, Royce-Rogers E, Elliott GM, et al., 2018, Salt thickness and composition influence rift structural style, northern North Sea, offshore Norway, Basin Research, ISSN: 0950-091X
‘Salt’ giants are typically halite‐dominated, although they invariably contain other evaporite (e.g. anhydrite, bittern salts) and non‐evaporite (e.g. carbonate, clastic) rocks. Rheological differences between these rocks mean they impact or respond to rift‐related, upper crustal deformation in different ways. Our understanding of basin‐scale lithology variations in ancient salt giants, what controls this, and how this impacts later rift‐related deformation, is poor, principally due to a lack of subsurface datasets of sufficiently regional extent. Here we use 2D seismic reflection and borehole data from offshore Norway to map compositional variations within the Zechstein Supergroup (Lopingian), relating this to the structural styles developed during Middle Jurassic‐to‐Early Cretaceous rifting. Based on the proportion of halite, we identify and map four intrasalt depositional zones (sensu Clark et al., 1998) offshore Norway. We show that, at the basin margins, the Zechstein Supergroup is carbonate‐dominated, whereas towards the basin centre, it become increasingly halite‐dominated, a trend observed in the UK sector of the North Sea Basin and in other ancient salt giants. However, we also document abrupt, large magnitude compositional and thickness variations adjacent to large, intra‐basin normal faults; for example, thin, carbonate‐dominated successions occur on fault‐bounded footwall highs, whereas thick, halite‐dominated successions occur only a few kilometres away in adjacent depocentres. It is presently unclear if this variability reflects variations in syn‐depositional relief related to flooding of an underfilled presalt (Early Permian) rift or syn‐depositional (Lopingian) rift‐related faulting. Irrespective of the underlying controls, variations in salt composition and thickness influenced the Middle Jurassic‐to‐Early Cretaceous rift structural style, with diapirism characterising hangingwall basins where autochthonous salt was thick and halite‐rich
Jackson CAL, 2018, Growth of a Salt-Detached Normal Fault and Controls on Throw Rate Variability; Gudrun Field, South Viking Graben, Offshore Norway, Rift-related coarse-grained submarine fan reservoirs; the Brae Play, South Viking Graben, North Sea, Editors: Turner, Cronin, Publisher: AAPG, Pages: 423-444, ISBN: 978-0-89181-395-8
The growth and throw/displacement rate variability on normal faults can reflect fault interaction, plate tectonic forces and, in gravity-driven systems, variations in sediment loading. Because earthquakes may occur as faults slip, it is important to understand what processes influence throw rate variability on normal faults to be able to predict seismic hazards in extensional terranes. Furthermore, the rate of normal fault growth directly controls rift physiography, sediment erosion, dispersal and deposition, and the distribution and stratigraphic architecture of syn-rift reservoirs. Instrumental (e.g. geodetic) data may constrain the very short-term (i.e. days to years) throw rate history of normal faults, whereas palaeoearthquake data may provide important information on medium-term (i.e. 103-105 years) rates. Constraining longer-term (i.e. >106 Myr) variations typically requires the use of seismic reflection data, although their application may be problematic because of poor seismic resolution and the absence of, or poor age constraints on, coeval growth strata. In this study I use 3D seismic reflection and borehole data to constrain the growth and long-term throw rate variability on a gravity-driven, salt-detached normal fault (Middle-to-Late Jurassic) in the South Viking Graben, offshore Norway, and to assess the impact of throw rate variability on the thickness and character of syn-rift reservoirs. I recognise five kinematic phases: (i) Phase 1 (early Callovian) - fault initiation and a phase of moderate fault throw rates (0.06 mm yr-1); (ii) Phase 2 (early Callovian-to-end Callovian) - fault inactivity, during which time the fault was buried by sediment; (iii) Phase 3 (early Oxfordian-to-late Oxfordian) - fault reactivation and a phase of moderate throw rates (up to 0.03 mm yr-1); (iv) Phase 4 (late Oxfordian-to-end Oxfordian) – a marked increase in throw rate (up to 0.27 mm yr-1); and (v) Phase 5 (early Kimmeridgian-to-middle Volgian) – a decl
Turner CC, Cronin BT, Riley LA, et al., 2018, The South Viking Graben: Overview of Upper Jurassic Rift Geometry, Biostratigraphy, and Extent of Brae Play Submarine Fan Systems, Rift-related coarse-grained submarine fan reservoirs; the Brae Play, South Viking Graben, North Sea, Publisher: AAPG, Pages: 9-38, ISBN: 978-0-89181-395-8
The South Viking Graben (SVG) hosts many large oil and gas condensate reservoirs, some within Middle Jurassic and Cenozoic rocks, but most within thick submarine fan sandstone and conglomerate sequences of the Upper Jurassic Brae Formation and their correlative equivalents, collectively termed here the Brae Play. Regional studies carried out over the last few years (based on the extensive well database and a variety of 3-D seismic data) and the recent acquisition of extensive, high-quality, broadband 3-D seismic data across the SVG have led to better definition of the half-graben geometry and the extents of the Upper Jurassic submarine fans that host these hydrocarbon accumulations. A summary structure map, seismic sections that extend across the graben, and a 3-D image of the “Base Cretaceous” are used to illustrate the main structural features. On its western side, the top of an eroded scarp, which grades downdip into the major fault plane, can be used as the lateral limit of the postrift graben fill. The uppermost Kimmeridge Clay Formation (KCF; termed Draupne Formation in Norway), which is the top seal and dominant source rock for Brae Play fields, onlaps this eroded slope and limits the western extent of the synrift section. At depth, the top of the prerift Bathonian Sleipner Formation can be mapped along this fault margin abutting the uneroded footwall fault; this boundary defines the edge of the thickest Upper Jurassic synrift section within the graben. The top of the prerift section becomes progressively shallower to the east, where an approximate minimum limit of the graben can be defined along much of its length by the eastern limit of seismically mappable KCF (Draupne) Formation. Thick sequences of Upper Jurassic conglomerates and sandstones within the KCF (i.e., the Brae Formation) were deposited as submarine fans within the graben. Most sediment was derived from the west (i.e., the Fladen Ground Spur), but some important fan systems were fed
Bastow IA, Booth AD, Corti G, et al., 2018, The development of late-stage continental breakup: seismic reflection and borehole evidence from the Danakil Depression, Ethiopia, Tectonics, Vol: 37, Pages: 2848-2862, ISSN: 0278-7407
During continental breakup, the locus of strain shifts from a broad region of border faulting and ductile plate stretching to a narrow zone of magma intrusion in a young ocean basin. Recent studies of volcanic rifts and margins worldwide suggest this shift occurs sub‐aerially, before the onset of seafloor spreading. We test this hypothesis using recently‐acquired seismic reflection and borehole data from the Danakil Depression, Ethiopia, a unique region of transition between continental rifting and seafloor spreading. Our data, located near Dallol, ~30km northwest of the Erta'Ale Volcanic Segment (EAVS), reveal a remarkably‐thick (>1km) sequence of young (~100ka) evaporites in a basin bound by a major (≤400m throw), east‐dipping normal fault. To generate such a large amount of subsidence in such a relatively short time, we propose that upper‐crustal extension in Danakil is currently dominated by faulting, not magmatic intrusion. Given the region's markedly thinned crust (~15‐km‐thick), relative to elsewhere in Afar where magma‐assisted rifting dominates and maintains crustal thickness at ~25km, mechanical extension in Danakil is likely coupled with ductile extension of the lower‐crust and mantle lithosphere. Despite proximity to the voluminous lavas of the active EAVS, evidence for igneous material in the upper ~2km of the 6–10‐km‐wide basin is limited. Late‐stage stretching was likely aided by thermal/strain‐induced lithospheric weakening following protracted magma‐assisted rifting. Basin formation immediately prior to the onset of seafloor spreading may also explain the accumulation of thick marine‐seepage‐fed evaporite sequences akin to those observed, for example, along the South Atlantic rifted margins.
Normal faults grow via synchronous increase in displacement and length (‘propagating fault model’, also known as the ‘isolated fault model’), or by rapid length establishment and subsequent displacement accrual (constant-length fault model). We here use time-series displacement (D) and length (L) data from natural and experimental faults to elucidate growth styles and D-L trajectories throughout fault life, and to assess the applicability of the two fault models. We show that the growth of most faults is characterized by two stages, with the first defined by fault lengthening (20–30% of fault lifespan) and the second by displacement accrual (70–80% of fault lifespan). Although broadly adhering to the constant-length model, fault growth throughout the lengthening stage, during which significant displacement (10–60% of the total end-of-life fault displacement) may also accumulate, is achieved through rapid tip propagation, relay breaching, and segment linkage, characteristics perhaps most intuitively thought to reflect growth in accordance with the propagating model. The subsequent growth stage is dominated by displacement accrual with limited lateral tip propagation, a phenomenon best described by the constant-length model. We also show that, despite being used primarily in support of the propagating model, global displacement-length (D-L) datasets are equally compatible with the constant-length model.
Jackson CA-L, Zhang Y, Herron D, et al., 2018, Subsurface expression of a salt weld, Gulf of Mexico, Petroleum Geoscience, ISSN: 1354-0793
Salt welds form due to salt expulsion and thinning by mechanical (e.g. salt flow) and/or chemical (e.g. salt dissolution) processes. Despite being ubiquitous in salt-bearing sedimentary basins, where they may trap large volumes of hydrocarbons, little is published on weld thickness and composition. We here use 3D seismic reflection, borehole, and biostratigraphic data from the Atwater Valley protraction area of the northern Gulf of Mexico to constrain the thickness and composition of a tertiary salt weld. Seismic data image an ‘apparent weld’ (sensu Wagner & Jackson 2011) at the base of a Plio-Pleistocene minibasin that subsided into allochthonous salt. Borehole data indicate the weld is actually ‘incomplete’, being c. 24 m thick, and containing an upper 5 m thick halite and a lower 15 m thick halite, separated by a 4 m thick mudstone. The age and origin of the intra-weld mudstone is unclear, although we speculate it is either: (i) Late Jurassic, representing material transported upwards from the autochthonous level within a feeder, and subsequently trapped as allochthonous salt thinned and welded, or, perhaps more likely; (ii) Pliocene, representing a piece of salt carapace reworked from the top of and eventually trapped in, the now locally welded sheet. We show that 3D seismic reflection data may not resolve salt weld thickness, with the presence of relatively thin remnant salt lending support to models of welding based on viscous flow. Furthermore, the halite-dominated character of the weld supports the hypothesis that tectonic purification may occur during salt flow.
Pichel LM, Peel FJ, Jackson CA-L, et al., 2018, Geometry and kinematics of salt-detached ramp syncline basins, Journal of Structural Geology, Vol: 115, Pages: 208-230, ISSN: 0191-8141
Ramp-syncline basins (RSBs) are characterized by asymmetric depocentres formed by translation above salt detachments with basal steps. Recognition of these minibasins allows quantification of the magnitude and rates of overburden translation above a deforming salt layer. 3D seismic data from the São Paulo Plateau, Santos Basin, Brazil image a series of RSBs formed above thick salt, and distributed above and/or basinward of pronounced base-salt steps. The RSBs are composed of landward-dipping and gently folded sigmoidal strata, recording 28–32 km of SE-directed translation during the Late Cretaceous and Paleocene, at an average rate of 0.8–0.9 mm/year. We present several examples of RSBs, in addition to results from numerical forward models, to analyse the 3D kinematics of RSBs and their interaction with base-salt structures. The RSBs form not only by translation above basinward-dipping ramps, but also over landward-dipping ramps. Translation over stepped ramps generates stacked RSBs. Thickness maps show translation is higher at the centre of RSBs and that depocentres become progressively more affected by diapirism as they evolve. This study presents the first analysis of the 3D kinematics of ramp-syncline basins, and the first documentation of their occurrence above thick salt in the Santos Basin, Brazil. It applies realistic numerical models that treat the detachment as a volume of viscous material, improving our understanding of these systems. RSBs are important to understand slope and deep-basin tectono-stratigraphic architecture of supra-salt units and can also guide the identification of pre-salt structures, thus contributing to the exploration of salt basins.
Magee C, Muirhead J, Schofield N, et al., 2018, Structural signatures of igneous sheet intrusion propagation, Journal of Structural Geology, ISSN: 0191-8141
The geometry and distribution of planar igneous bodies (i.e. sheet intrusions), such as dykes, sills, and inclined sheets, has long been used to determine emplacement mechanics, define melt source locations, and reconstruct palaeostress conditions to shed light on various tectonic and magmatic processes. Since the 1970's we have recognised that sheet intrusions do not necessarily display a continuous, planar geometry, but commonly consist of segments. The morphology of these segments and their connectors is controlled by, and provide insights into, the behaviour of the host rock during emplacement. For example, tensile brittle fracturing leads to the formation of intrusive steps or bridge structures between adjacent segments. In contrast, brittle shear faulting, cataclastic and ductile flow processes, as well as heat-induced viscous flow or fluidization, promotes magma finger development. Textural indicators of magma flow (e.g., rock fabrics) reveal that segments are aligned parallel to the initial sheet propagation direction. Recognising and mapping segment long axes thus allows melt source location hypotheses, derived from sheet distribution and orientation, to be robustly tested. Despite the information that can be obtained from these structural signatures of sheet intrusion propagation, they are largely overlooked by the structural and volcanological communities. To highlight their utility, we briefly review the formation of sheet intrusion segments, discuss how they inform interpretations of magma emplacement, and outline future research directions.
Duffy OB, Dooley TP, Hudec MR, et al., 2018, Structural Evolution of Salt-Influenced Fold-and-Thrust belts: A Synthesis and New Insights From Basins Containing Isolated Salt Diapirs, Journal of Structural Geology, ISSN: 0191-8141
Lateral shortening is expressed in unique ways in salt basins, especially if pre-shortening diapirs are present. We present an overview and new 3-D conceptual models capturing the evolution of shortening structures formed in salt provinces dominated by precursor isolated diapirs (termed isolated-diapir provinces). In such provinces, isolated diapirs form only a minor volumetric component of a sedimentary basin, however, due to the relative weakness of rock salt and their ability to localize strain, during shortening they have a disproportionately large influence on structural development. We find three key mechanical principles govern the processes and structural styles developed during shortening of isolated-diapir provinces. First, salt diapirs shorten before surrounding sedimentary rocks due to their relative weakness, and so form salients in the thrust front during early shortening. Second, diapirs tend to nucleate folds and faults, which radiate out from the diapirs. Third, as diapir walls converge, the roof must shorten. Extrusive salt sheets are expelled through thin roofs, but thicker roofs resist piercement and so tend to undergo complex folding and faulting. As a result of these principles, the first-order controls on the structural styles expressed across a shortened isolated-diapir province are the pre-shortening configuration of diapirs, the connectivity of the diapirs prior to shortening, total strain magnitude, and diapir roof thickness. Second-order controls include the initial cross-sectional and map-view geometry of diapirs, diapir size, and diapir orientation with respect to the shortening direction.
Coleman AJ, Jackson CA-L, Duffy OB, et al., 2018, How, where, and when do radial faults grow near salt diapirs?, GEOLOGY, Vol: 46, Pages: 655-658, ISSN: 0091-7613
Godefroy G, Caumon G, Ford M, et al., 2018, A parametric fault displacement model to introduce kinematic control into modeling faults from sparse data, INTERPRETATION-A JOURNAL OF SUBSURFACE CHARACTERIZATION, Vol: 6, Pages: B1-B13, ISSN: 2324-8858
Phillips TB, Jackson CA-L, Bell RE, et al., 2018, Oblique reactivation of lithosphere-scale lineaments controls rift physiography-the upper-crustal expression of the Sorgenfrei-Tornquist Zone, offshore southern Norway, SOLID EARTH, Vol: 9, Pages: 403-429, ISSN: 1869-9510
Phillips TB, Magee C, Jackson CA-L, et al., 2018, Determining the three-dimensional geometry of a dike swarm and its impact on later rift geometry using seismic reflection data, GEOLOGY, Vol: 46, Pages: 119-122, ISSN: 0091-7613
Ortiz-Karpf A, Hodgson DM, Jackson CA-L, et al., 2018, Mass-transport complexes as markers of deep-water fold-and-thrust belt evolution: insights from the southern Magdalena fan, offshore Colombia, BASIN RESEARCH, Vol: 30, Pages: 65-88, ISSN: 0950-091X
Rodriguez CR, Jackson CA-L, Rotevatn A, et al., 2018, Dual tectonic-climatic controls on salt giant deposition in the Santos Basin, offshore Brazil, GEOSPHERE, Vol: 14, Pages: 215-242, ISSN: 1553-040X
Dmitrieva E, Jackson CA-L, Huuse M, et al., 2018, Regional distribution and controls on the development of post-rift turbidite systems: insights from the Paleocene of the eastern North Viking Graben, offshore Norway, 8th Petroleum Geology Conference (PGC), Publisher: GEOLOGICAL SOC PUBLISHING HOUSE, Pages: 147-170, ISSN: 2047-9921
Reeve MT, 2018, Tectonic and oceanographic process interactions archived in Late Cretaceous to Present deep-marine stratigraphy on the Exmouth Plateau, offshore NW Australia, Basin Research, ISSN: 0950-091X
© 2018 The Authors. Basin Research © 2018 International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd Deep-marine deposits provide a valuable archive of process interactions between sediment gravity flows, pelagic sedimentation and thermohaline bottom-currents. Stratigraphic successions can also record plate-scale tectonic processes (e.g. continental breakup and shortening) that impact long-term ocean circulation patterns, including changes in climate and biodiversity. One such setting is the Exmouth Plateau, offshore NW Australia, which has been a relatively stable, fine-grained carbonate-dominated continental margin from the Late Cretaceous to Present. We combine extensive 2D (~40,000 km) and 3D (3,627 km2) seismic reflection data with lithologic and biostratigraphic information from wells to reconstruct the tectonic and oceanographic evolution of this margin. We identified three large-scale seismic units (SUs): (a) SU-1 (Late Cretaceous)—500 m-thick, and characterised by NE-SW-trending, slope-normal elongate depocentres (c. 200 km long and 70 km wide), with erosional surfaces at their bases and tops, which are interpreted as the result of contour-parallel bottom-currents, coeval with the onset of opening of the Southern Ocean; (b) SU-2 (Palaeocene—Late Miocene)—800 m-thick and characterised by: (a) very large (amplitude, c. 40 m and wavelength, c. 3 km), SW-migrating, NW-SE-trending sediment waves, (b) large (4 km-wide, 100 m-deep), NE-trending scours that flank the sediment waves and (c) NW-trending, 4 km-wide and 80 m-deep turbidite channel, infilled by NE-dipping reflectors, which together may reflect an intensification of NE-flowing bottom currents during a relative sea-level fall following the establishment of circumpolar-ocean current around Antarctica; and (c) SU-3 (Late Miocene—Present)—1,000&n
Patruno S, Reid W, Jackson CA-L, et al., 2018, New insights into the unexploited reservoir potential of the Mid North Sea High (UKCS quadrants 35-38 and 41-43): a newly described intra-Zechstein sulphate-carbonate platform complex, 8th Petroleum Geology Conference (PGC), Publisher: GEOLOGICAL SOC PUBLISHING HOUSE, Pages: 87-124, ISSN: 2047-9921
Reeves J, Magee C, Jackson C, 2018, Unravelling intrusion-induced forced fold kinematics and ground deformation using 3D seismic reflection data, Volcanica, Pages: 1-17
Wrona T, Magee C, Jackson CA-L, et al., 2017, Kinematics of Polygonal Fault Systems: Observations from the Northern North Sea, FRONTIERS IN EARTH SCIENCE, Vol: 5, ISSN: 2296-6463
Claringbould JS, Bell RE, Jackson CA-L, et al., 2017, Pre-existing normal faults have limited control on the rift geometry of the northern North Sea, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 475, Pages: 190-206, ISSN: 0012-821X
Childs C, Holdsworth RW, Jackson CA-L, et al., 2017, Introduction to the geometry and growth of normal faults, Geometry and Growth of Normal Faults, Publisher: Geological Society of London, Pages: 1-9
Deng C, Fossen H, Gawthorpe RL, et al., 2017, Influence of fault reactivation during multiphase rifting: The Oseberg area, northern North Sea rift, MARINE AND PETROLEUM GEOLOGY, Vol: 86, Pages: 1252-1272, ISSN: 0264-8172
Coleman AJ, Jackson CA-L, Duffy OB, 2017, Balancing sub- and supra-salt strain in salt-influenced rifts: Implications for extension estimates, JOURNAL OF STRUCTURAL GEOLOGY, Vol: 102, Pages: 208-225, ISSN: 0191-8141
Turrini L, Jackson CA-L, Thompson P, 2017, Seal rock deformation by polygonal faulting, offshore Uruguay, MARINE AND PETROLEUM GEOLOGY, Vol: 86, Pages: 892-907, ISSN: 0264-8172
Schmiedel T, Kjoberg S, Planke S, et al., 2017, Mechanisms of overburden deformation associated with the emplacement of the Tulipan Sill, mid-Norwegian margin, Interpretation, Vol: 5, Pages: SK23-SK38, ISSN: 0020-9635
The emplacement of igneous intrusions into sedimentary basins mechanically deforms the host rocks and causes hydrocarbon maturation. Existing models of host-rock deformation are investigated using high-quality 3D seismic and industry well data in the western Møre Basin offshore mid-Norway. The models include synemplacement (e.g., elastic bending-related active uplift and volume reduction of metamorphic aureoles) and postemplacement (e.g., differential compaction) mechanisms. We use the seismic interpretations of five horizons in the Cretaceous-Paleogene sequence (Springar, Tang, and Tare Formations) to analyze the host rock deformation induced by the emplacement of the underlying saucer-shaped Tulipan sill. The results show that the sill, emplaced between 55.8 and 54.9 Ma, is responsible for the overlying dome structure observed in the seismic data. Isochron maps of the deformed sediments, as well as deformation of the younger postemplacement sediments, document a good match between the spatial distribution of the dome and the periphery of the sill. The thickness t of the Tulipan is less than 100 m, whereas the amplitude f of the overlying dome ranges between 30 and 70 m. Spectral decomposition maps highlight the distribution of fractures in the upper part of the dome. These fractures are observed in between hydrothermal vent complexes in the outer parts of the dome structure. The 3D seismic horizon interpretation and volume rendering visualization of the Tulipan sill reveal fingers and an overall saucer-shaped geometry. We conclude that a combination of different mechanisms of overburden deformation, including (1) elastic bending, (2) shear failure, and (3) differential compaction, is responsible for the synemplacement formation and the postemplacement modification of the observed dome structure in the Tulipan area.Read More: https://library.seg.org/doi/abs/10.1190/INT-2016-0155.1
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