Search or filter publications

Filter by type:

Filter by publication type

Filter by year:



  • Showing results for:
  • Reset all filters

Search results

    Davies DR, Goes S, Lau HCP, 2015,

    Thermally dominated deep mantle LLSVPs: A review

    , The Earth’s Heterogeneous Mantle: a geophysical, geodynamical, geochemical perspective, Editors: Khan, Deschamps, Publisher: Springer, Pages: 441-477

    The two large low shear-wave velocity provinces (LLSVPs) that dominate lower-mantle structure may hold key information on Earth’s thermal and chemical evolution. It is generally accepted that these provinces are hotter than background mantle and are likely the main source of mantle plumes. Increasingly, it is also proposed that they hold a dense (primitive and/or recycled) compositional com- ponent. The principle evidence that LLSVPs may represent thermo-chemical ‘piles’ comes from seismic constraints, including: (i) their long-wavelength nature; (ii) sharp gradients in shear-wave velocity at their margins; (iii) non-Gaussian distributions of deep mantle shear-wave velocity anomalies; (iv) anti-correlated shear-wave and bulk-sound velocity anomalies (and elevated ratios between shear- and compressional-wave velocity anomalies); (v) anti-correlated shear-wave and density anomalies; and (vi) 1-D/radial profiles of seismic velocity that deviate from those expected for an isochemical, well-mixed mantle. In addition, it has been proposed that hotspots and the reconstructed eruption sites of large ig- neous provinces correlate in location with LLSVP margins. In this paper, we review recent results which indicate that the majority of these constraints do not require thermo-chemical piles: they are equally well (or poorly) explained by thermal heterogeneity alone. Our analyses and conclusions are largely based on comparisons between imaged seismic structure and synthetic seismic structures from a set of thermal and thermo-chemical mantle convection models, which are constrained by ∼ 300 Myr of plate motion histories. Modelled physical structure (temperature, pressure and composition) is converted into seismic velocities via a thermodynamic approach that accounts for elastic, anelastic and phase con- tributions and, subsequently, a tomographic resolution filter is applied to account for the damping and geographic bias inherent to seismic imaging. Our re

    Davies DR, Goes S, Sambridge M, 2015,

    On the relationship between volcanic hotspot locations, the reconstructed eruption sites of large igneous provinces and deep mantle seismic structure

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 411, Pages: 121-130, ISSN: 0012-821X
    Dejong BD, Bierman PR, Newell WL, Rittenour TM, Mahan SA, Balco G, Rood DHet al., 2015,

    Pleistocene relative sea levels in the Chesapeake Bay region and their implications for the next century

    , GSA Today, Vol: 25, Pages: 4-10, ISSN: 1052-5173

    Today, relative sea-level rise (3.4 mm/yr) is faster in the Chesapeake Bay region than any other location on the Atlantic coast of North America, and twice the global average eustatic rate (1.7 mm/yr). Dated interglacial deposits suggest that relative sea levels in the Chesapeake Bay region deviate from global trends over a range of timescales. Glacio-isostatic adjustment of the land surface from loading and unloading of continental ice is likely responsible for these deviations, but our understanding of the scale and timeframe over which isostatic response operates in this region remains incomplete because dated sea-level proxies are mostly limited to the Holocene and to deposits 80 ka or older. To better understand glacio-isostatic control over past and present relative sea level, we applied a suite of dating methods to the stratigraphy of the Blackwater National Wildlife Refuge, one of the most rapidly subsiding and lowest-elevation surfaces bordering Chesapeake Bay. Data indicate that the region was submerged at least for portions of marine isotope stage (MIS) 3 (ca. 60-30 ka), although multiple proxies suggest that global sea level was 40-80 m lower than present. Today MIS 3 deposits are above sea level because they were raised by the Last Glacial Maximum forebulge, but decay of that same forebulge is causing ongoing subsidence. These results suggest that glacio-isostasy controlled relative sea level in the mid-Atlantic region for tens of thousands of years following retreat of the Laurentide Ice Sheet and continues to influence relative sea level in the region. Thus, isostatically driven subsidence of the Chesapeake Bay region will continue for millennia, exacerbating the effects of global sea-level rise and impacting the region's large population centers and valuable coastal natural resources.

    Dilib FA, Jackson MD, Zadeh AM, Aasheim R, Arland K, Gyllensten AJ, Erlandsen SMet al., 2015,

    Closed-Loop Feedback Control in Intelligent Wells: Application to a Heterogeneous, Thin Oil-Rim Reservoir in the North Sea

    , SPE RESERVOIR EVALUATION & ENGINEERING, Vol: 18, Pages: 69-83, ISSN: 1094-6470
    Doherty P, Igoe D, Murphy G, Gavin K, Preston J, McAvoy C, Byrne BW, Mcadam R, Burd HJ, Houlsby GT, Martin CM, Zdravkovic L, Taborda DMG, Potts DM, Jardine RJ, Sideri M, Schroeder FC, Wood AM, Kallehave D, Gretlund JSet al., 2015,

    Field validation of fibre Bragg grating sensors for measuring strain on driven steel piles

    , GEOTECHNIQUE LETTERS, Vol: 5, Pages: 74-79, ISSN: 2049-825X
    Dooley TP, Jackson MPA, Jackson CA-L, Hudec MR, Rodriguez CRet al., 2015,

    Enigmatic structures within salt walls of the Santos Basin—Part 2: Mechanical explanation from physical modeling

    , Journal of Structural Geology, Vol: 75, Pages: 163-187, ISSN: 0191-8141

    Jackson et al. (this volume) used 3D seismic reflection data to describe intrasalt deformation in salt walls in the Santos Basin. They focused on the origin of enigmatic allochthonous salt sheets of older evaporites (A1 unit) emplaced above overlying stratified evaporites (A2–A4 units). Their kinematic model incorporates: (i) initial inward flow and thickening of A1 salt within the rising wall, and arching of A2–A4 overburden; (ii) breaching of the arched overburden, ascent of mobile A1 evaporites along single or multiple feeders, and emplacement of upper-wall sheets or canopies; and (iii) a component of regional shortening within the salt. This companion paper uses physical modeling to explain how and why these structures occur and proposes a mechanical basis for the kinematic model. Our first two models simulated salt having uniform internal density, with walls growing by (i) initially symmetric differential loading and (ii) initially symmetric differential loading plus shortening. These models reproduced anticlines and injection folds seen in the simpler deformed walls in the Santos Basin. However, neither model reproduced the most complex structures within the Santos evaporites, which are: (i) allochthonous intrusions, (ii) steep feeders, and (iii) recumbent synclines. Thus, differential loading and shortening alone are insufficient to generate these complex structures. In our third model, a less-dense lower evaporite (A1) was overlain by denser upper evaporites (A2–A4), similar to the density structure found by Santos Basin wellbores. The wall rose solely by differential loading. In this model, A1 breached the overlying evaporites to form vertical diapirs feeding salt sheets and salt wings in the upper part of the salt wall. Breakthrough of A1 folded A2–A4 evaporites into recumbent synclines. Model sections closely resemble Santos seismic examples, suggesting that the key to forming these complex intrasalt structures is a density inversi

    Dubasaru V, Zdravkovic L, Taborda DMG, Hardy Set al., 2015,

    Influence of pile raft stiffness on building behaviour in a tunnel-pile clash scenario

    , Pages: 455-460

    © The authors and ICE Publishing: All rights reserved, 2015. In a modern urban environment, the underground space becomes increasingly congested due to the high value of the land that forces the new infrastructure projects to be constructed deeper into the ground. For each new project, the potential of both expected and unexpected clashes between new tunnel alignments and the foundations of the existing structures becomes more probable. However, to date, the research on tunnel-pile clashes has been scarce. In the current study, the effects of such a situation are studied by carrying out finite element analyses for a scenario that is typical in the London ground profile. A parametric study was conducted to investigate the influence of the pile raft bending stiffness on the building settlement and the change in piles' axial forces. It is shown that an increased raft bending stiffiiess helps to transfer the load from the trimmed pile to the adjacent piles, thus reducing the settlement of the trimmed pile. In the process of tunnel excavation, the pile settles due to the soil-induced downdrag and the loss of both its base and part of its shaft capacity. It is concluded that the tunnel-pile clash has a large impact on the surface structure, piles and tunnel itself.

    Duffy OB, Bell RE, Jackson CA-L, Gawthorpe RL, Whipp PSet al., 2015,

    Fault growth and interactions in a multiphase rift fault network: Horda Platform, Norwegian North Sea

    , JOURNAL OF STRUCTURAL GEOLOGY, Vol: 80, Pages: 99-119, ISSN: 0191-8141
    Forman LV, Bland PA, Timms NE, Daly L, Collins GS, Davison TM, Trimby PW, Ringer SPet al., 2015,


    , 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, ISSN: 1086-9379
    Freitas TMB, Potts DM, Zdravkovic L, 2015,

    Numerical study on the response of two footings at Bothkennar research site

    , GEOTECHNIQUE, Vol: 65, Pages: 155-168, ISSN: 0016-8505
    Gavin K, Jardine RJ, Karlsrud K, Lehane BMet al., 2015,

    The Effects of Pile Ageing on the Shaft Capacity of Offshore Piles in Sand.

    , International Symposium Frontiers in Offshore Geotechnics, Publisher: CRC Press, Pages: 129-151

    A number of field studies suggest that the axial capacity of driven piles in sand increases withtime. Field test programmes were performed by a number of research groups to examine this aspect of pilebehaviour. The paper presents a summary of the findings from these experiments. It also reviews laboratorypile and element testing performed to provide further insights into the mechanisms controlling pile ageing.

    Ghail RC, Mason PJ, Skipper JA, 2015,

    The geological context and evidence for incipient inversion of the London Basin

    , Pages: 3523-3528

    © The authors and ICE Publishing: All rights reserved, 2015. A reappraisal of ground investigation data across London reveal that a range of unexpected ground conditions, encountered in engineering works since Victorian times, may result from the effects of ongoing inversion of the London Basin. Site investigation borehole data and the distribution of river terrace deposits of the Thames and its tributaries reveal a complex pattern of block movements, tilting and dextral transcurrent displacement. Significant displacements (∼10 m) observed in Thames terrace gravels in borehole TQ38SE1565 at the Lower Lea Crossing, showing that movement has occurred within the last ∼100 ka. Restraining bends on reactivated transcurrent faults may explain the occurrence of drift filled hollows, previously identified as fluvially scoured pingos, by faulting and upward migration of water on a flower structure under periglacial conditions. Mapping the location of these features constrains the location of active transcurrent faults and so helps predict the likelihood of encountering hazardous ground conditions during tunnelling and ground engineering.

    Gold PO, Behr WM, Rood D, Sharp WD, Rockwell TK, Kendrick K, Salin Aet al., 2015,

    Holocene geologic slip rate for the Banning strand of the southern San Andreas Fault, southern California

    , JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 120, Pages: 5639-5663, ISSN: 2169-9313
    Graham GH, Jackson MD, Hampson GJ, 2015,

    Three-dimensional modeling of clinoforms in shallow-marine reservoirs: Part 2. Impact on fluid flow and hydrocarbon recovery in fluvial-dominated deltaic reservoirs

    , AAPG Bulletin, Vol: 99, Pages: 1049-1080, ISSN: 0149-1423

    © 2015. The American Association of Petroleum Geologists. All rights reserved. Permeability contrasts associated with clinoforms have been identified as an important control on fluid flow and hydrocarbon recovery in fluvial-dominated deltaic parasequences. However, they are typically neglected in subsurface reservoir models or considered in isolation in reservoir simulation experiments because clinoforms are difficult to capture using current modeling tools. A suite of three-dimensional reservoir models constructed with a novel, stochastic, surface-based clinoform-modeling algorithm and outcrop analog data (Upper Cretaceous Ferron Sandstone Member, Utah) have been used here to quantify the impact of clinoforms on fluid flow in the context of (1) uncertainties in reservoir characterization, such as the presence of channelized fluvial sandbodies and the impact of bed-scale heterogeneity on vertical permeability, and (2) reservoir engineering decisions, including oil production rate. The proportion and distribution of barriers to flow along clinoforms exert the greatest influence on hydrocarbon recovery; equivalent models that neglect these barriers overpredict recovery by up to 35%. Continuity of channelized sandbodies that cut across clinoform tops and vertical permeability within distal delta-front facies influence sweep within clinothems bounded by barriers. Sweep efficiency is reduced when producing at higher rates over shorter periods, because oil is bypassed at the toe of each clinothem. Clinoforms are difficult to detect using production data, but our results indicate that they significantly influence hydrocarbon recovery and their impact is typically larger than that of other geologic heterogeneities regardless of reservoir engineering decisions. Clinoforms should therefore be included in models of fluvial-dominated deltaic reservoirs to accurately predict hydrocarbon recovery and drainage patterns.

    Graham GH, Jackson MD, Hampson GJ, 2015,

    Three-dimensional modeling of clinoforms in shallow-marine reservoirs: Part 1. Concepts and application

    , AAPG BULLETIN, Vol: 99, Pages: 1013-1047, ISSN: 0149-1423
    Han B, Yang Z, Zdravkovic L, Kontoe Set al., 2015,

    Non-linearity of gravelly soils under seismic compressional deformation based on KiK-net downhole array observations

    , GEOTECHNIQUE LETTERS, Vol: 5, Pages: 287-293, ISSN: 2049-825X
    Han B, Zdravkovic L, Kontoe S, 2015,

    Stability investigation of the Generalised-alpha time integration method for dynamic coupled consolidation analysis

    , COMPUTERS AND GEOTECHNICS, Vol: 64, Pages: 83-95, ISSN: 0266-352X
    Holgate NE, Jackson CA-L, Hampson GJ, Dreyer Tet al., 2015,

    Seismic stratigraphic analysis of the Middle-Upper Jurassic Krossfjord and Fensfjord formations, Troll oil and gas field, northern North Sea

    , Marine and Petroleum Geology, Vol: 68, Pages: 352-380, ISSN: 1873-4073

    The “syn-rift” Middle-to-Late Jurassic Krossfjord and Fensfjord formations, Troll Field, northern North Sea contain a complex distribution of wave- and tide-dominated deltaic, shoreline and shelf depositional environments of varying reservoir potential. Uncertainty exists in depositional models used to explain the spatial and temporal distribution of these depositional environments and the absence of coeval coastal plain deposits. To date, the proposed influence of growing rift-related structures on stratigraphic architectures and sedimentation patterns in the units has been poorly defined. In this study, 3D seismic data are integrated with core, biostratigraphic and wireline-log data to produce a consistent geological interpretation for the formations. Seismic analysis has identified nine parasequences (‘series’) containing NNE-SSW-striking, delta-scale clinoforms that prograded westwards over much of the field. Quantitative analysis highlights an increase in height and dip of clinoforms from proximal to distal locations, coincident with an increase in grain size. Clinoform geometry is sigmoidal, with well-developed topsets that, based on core data, lack subaerial deposits. These geometrical and sedimentological characteristics suggest that a subaqueous delta depositional system deposited the Krossfjord and Fensfjord formations in the Troll Field. In the northeast of the field, clinoforms exhibit highly variable strike and oblique cross-sectional geometries, which suggest that sediment was supplied from here, and then redistributed through southward-directed wave and longshore current activity. Rift-related faulting is recognised to have occurred in thewestern part of the Troll Field only during deposition of the youngest Fensfjord Formation ‘series’, thus challenging the notion that these units are ‘syn-rift’. Seismically imaged clinoforms in the under-explored area south of the Troll Field prograded southward, and a

    Jackson CA-L, Jackson MPA, Hudec MR, 2015,

    Understanding the kinematics of salt-bearing passive margins: A critical test of competing hypotheses for the origin of the Albian Gap, Santos Basin, offshore Brazil

    , GEOLOGICAL SOCIETY OF AMERICA BULLETIN, Vol: 127, Pages: 1730-1751, ISSN: 0016-7606
    Jackson CA-L, Jackson MPA, Hudec MR, Rodriguez CRet al., 2015,

    Enigmatic structures within salt walls of the Santos Basin—Part 1: Geometry and kinematics from 3D seismic reflection and well data

    , Journal of Structural Geology, Vol: 75, Pages: 135-162, ISSN: 0191-8141

    Understanding intrasalt structure may elucidate the fundamental kinematics and, ultimately, the mechanics of diapir growth. However, there have been relatively few studies of the internal structure of salt diapirs outside the mining industry because their internal parts are only partly exposed in the field and poorly imaged on seismic reflection data. This study uses 3D seismic reflection and borehole data from the São Paulo Plateau, Santos Basin, offshore Brazil to document the variability in intrasalt structural style in natural salt diapirs. We document a range of intrasalt structures that record: (i) initial diapir rise; (ii) rise of lower mobile halite through an arched and thinned roof of denser, layered evaporites, and emplacement of an intrasalt sheet or canopy; (iii) formation of synclinal flaps kinematically linked to emplacement of the intrasalt allochthonous bodies; and (iv) diapir squeezing. Most salt walls contain simple internal anticlines. Only a few salt walls contain allochthonous bodies and breakout-related flaps. All of these are in an area having a density inversion within the autochthonous salt layer, such that upper, anhydrite-rich, layered evaporites are denser than lower, more halite-rich evaporites. We thus interpret that most diapirs rose through simple fold amplification of internal salt stratigraphy but that locally, where a density inversion existed in the autochthonous salt, Rayleigh-Taylor overturn within the growing diapir resulted in the ascent of less dense evaporites into the diapir crest by breaching the internal anticline. This resulted in emplacement of high-level intrsalt allochthonous sheets underlain by breakout-related flaps and steep salt-ascension zones or feeders. Although late-stage regional shortening undoubtedly occurred on the São Paulo Plateau during the Late Cretaceous, we suggest this was only partly responsible for the complex intrasalt deformation. Although based on the Santos Basin, our kinematic

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: Request URI: /respub/WEB-INF/jsp/search-t4-html.jsp Query String: id=833&limit=20&page=6&respub-action=search.html Current Millis: 1508275216788 Current Time: Tue Oct 17 22:20:16 BST 2017