151 results found
Bastow ID, 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, ISSN: 0278-7407
©2018. The Authors. 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 subaerially, 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, ~30 km northwest of the Erta'Ale Volcanic Segment, reveal a remarkably thick (>1-km) sequence of young (~100-ka) evaporites in a basin bound by a major (≤400-m-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 ~25 km, 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 Erta'Ale Volcanic Segment, evidence for igneous material in the upper ~2 km of the 6- to 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.
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
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
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.
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
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.
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.
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
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
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
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.
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
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
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.
Alqahtani FA, Jackson CA-L, Johnson HD, et al., 2017, CONTROLS ON THE GEOMETRY AND EVOLUTION OF HUMID-TROPICAL FLUVIAL SYSTEMS: INSIGHTS FROM 3D SEISMIC GEOMORPHOLOGICAL ANALYSIS OF THE MALAY BASIN, SUNDA SHELF, SOUTHEAST ASIA, JOURNAL OF SEDIMENTARY RESEARCH, Vol: 87, Pages: 17-40, ISSN: 1527-1404
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
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
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
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
Duffy OB, Fernandez N, Hudec MR, et al., 2017, Lateral mobility of minibasins during shortening: Insights from the SE Precaspian Basin, Kazakhstan, JOURNAL OF STRUCTURAL GEOLOGY, Vol: 97, Pages: 257-276, ISSN: 0191-8141
Duffy OB, Nixon CW, Bell RE, et al., 2017, The topology of evolving rift fault networks: Single-phase vs multi-phase rifts, JOURNAL OF STRUCTURAL GEOLOGY, Vol: 96, Pages: 192-202, ISSN: 0191-8141
Elliott GM, Jackson CA-L, Gawthorpe RL, et al., 2017, Late syn-rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid-Norway; a test of rift basin tectono-stratigraphic models, BASIN RESEARCH, Vol: 29, Pages: 465-487, ISSN: 0950-091X
Fernandez N, Duffy OB, Hudec MR, et al., 2017, The origin of salt-encased sediment packages: Observations from the SE Precaspian Basin (Kazakhstan), JOURNAL OF STRUCTURAL GEOLOGY, Vol: 97, Pages: 237-256, ISSN: 0191-8141
Jackson, Rotevatn A, Tvedt BM, et al., 2017, The role of gravitational collapse in controlling the evolution of crestal faults systems (Espirito Santo Basin, SE Brazil) - Discussion, Journal of Structural Geology, Vol: 98, Pages: 95-97, ISSN: 0191-8141
Jackson CA-L, Bell RE, Rotevatn A, et al., 2017, Techniques to determine the kinematics of synsedimentary normal faults and implications for fault growth models, Pages: 187-217, ISSN: 0305-8719
Jackson CA-L, Holford SP, Magee C, et al., 2017, Subsurface expression of igneous systems and their impacts on petroleum systems, Interpretation, Vol: 5, Pages: SKi-SKiii, ISSN: 0020-9635
Lewis MM, Jackson CA-L, Gawthorpe RL, 2017, Tectono-sedimentary development of early syn-rift deposits: the Abura Graben, Suez Rift, Egypt, BASIN RESEARCH, Vol: 29, Pages: 327-351, ISSN: 0950-091X
Magee C, Bastow ID, de Vries BVW, et al., 2017, Structure and dynamics of surface uplift induced by incremental sill emplacement, GEOLOGY, Vol: 45, Pages: 431-434, ISSN: 0091-7613
Magee C, Jackson CA-L, Hardman JP, et al., 2017, Decoding sill emplacement and forced fold growth in the Exmouth Sub-basin, offshore northwest Australia: Implications for hydrocarbon exploration, INTERPRETATION-A JOURNAL OF SUBSURFACE CHARACTERIZATION, Vol: 5, Pages: SK11-SK22, ISSN: 2324-8858
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