Geolunch seminar @ UiB

Simone Masoch (Dipartimento di Geoscienze, Università degli Studi di Padova, Padua, Italy)
2022-11-02 12:00 - 13:00 (Europe/Oslo)
Structural evolution and architecture of an exhumed crustal-scale seismogenic fault (Bolfin Fault Zone, Atacama Fault System, Chile)
Simone Masoch
The architecture and spatio-temporal evolution of brittle fault zones play a pivotal role in earthquake mechanics, by controlling, for instance, the nucleation, propagation and arrest of individual seismic ruptures. Nevertheless, the along-strike architectural variability and structural evolution of crustal-scale seismogenic sources are still poorly investigated. Here, we describe the architectural variability and structural evolution of the >40-km-long, exhumed, seismogenic Bolfin Fault Zone (BFZ) of the intra-arc Atacama Fault System (Atacama Desert, Northern Chile). The BFZ has a sinuous crustal-scale geometry cutting through plutonic rocks of the Mesozoic Coastal Cordillera. Ancient (125-118 Ma) seismic faulting occurred at 5-7 km depth and ≤ 300 °C in a fluid-rich environment, as attested by widespread occurrence of pseudotachylytes (i.e., solidified frictional melts), and extensive chlorite-epidote veining and propylitic alteration. Moreover, the multiple cataclastic fault core strands are embedded within a strongly altered damage zone, which includes high-dilatant hydrothermal breccias and clusters of epidote-rich fault-vein networks at the linkage of the BFZ with subsidiary faults. We discuss how the geodynamic setting of the magmatic arc played a pivotal role in controlling the architecture and spatio-temporal evolution of the BFZ with reference to (i) spatial arrangement of precursory magmatic anisotropies (magmatic foliations of plutons and dyke swarm) exploited as loci of fault nucleation and (ii) large availability of fluids and heat during late cooling stages of the batholiths, triggering fluid-driven small-in-magnitude seismicity distributed within the BFZ damage zone.

Discussions - 1 minute presentation
2022-10-26 12:00 - 13:00

Ann Rowan
2022-10-19 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Quantifying terrestrial palaeoclimate variability from ice-marginal moraines
Glaciated landscapes contain moraines that record past glacier extent from which we can (in some cases) infer palaeoclimate. However, to do so, we need to bear in mind that glacier response to climate change is non-linear and that the sedimentary record created by glaciers is incomplete. We are using forward numerical modelling of moraine building and terrestrial cosmogenic nuclide exposure age-dating of moraine formation to search for palaeoclimate signals in glacial landscapes in Nepal and New Zealand.

Mar Moragas Rodriguez
2022-09-28 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
What can we learn from salt-basins field analogues? The Moroccan Central High Atlas revisited
Mar Moragas (Postdoktor ZechTec project, GBS)
The Central High Atlas was classically regarded as a failed Mesozoic rift arm subject to Alpine inversion, folding and thrusting with just isolated diapir structures reported. Compiled data from 4 years of field work in the Moroccan Atlas has revealed that the High Atlas region is a prolific salt-related rift basin with a complex network of salt structures and minibasins. To get a better understanding of the evolution of the basin, a multidisciplinary project was carried out by integrating sedimentary and structural observations, petrographic studies, geochemical analysis, and analogue and numerical modelling. In this presentation I will show some of the lessons learned from this diapiric system regarding the tectono-sedimentary evolution of the basin, subsidence analysis, linkage between pre- and post-salt deformation and diapir-controlled carbonate platform diagenesis.
Photo is from the Lake Plateau minibasin, where a younger Mar was figuring out how this minibasin evolved during Jurassic times.

Dawn Kellet
2022-09-21 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Dating deformation and exhumation in orogenic settings

My research career has focused on contributing to tectonic reconstructions of collisional (Himalaya, Trans-Hudson) and accretionary (Appalachian, Cordillera) orogens by constraining the timing of deformation and exhumation. To do this, I integrate structural and metamorphic petrology data with a wide range of geo- and thermochronometers including U-Pb, Lu-Hf, Ar-Ar, AFT, U-Th-He and Rb-Sr decay systems applied to diverse minerals. My active projects in the Canadian Cordillera and Canadian Appalachians pair focused studies to determine kinematics, timing and conditions of major reactivated fault zones with regional studies on exhumation and landscape evolution. I look forward to meeting many of you and am keen to learn from UiB’s expertise in structural geology, thermochronology and geodynamic modeling.

Photo is from field work this past summer. I had the opportunity to sample faults and gold veins in a historic (1930’s-1940’s) gold mine at the foot of a glacier about 60 km from Juneau, Alaska.

Special Geolunch seminars
2022-09-05 13:00 - 15:30 | Kvartsitten, 3rd floor, Realfalbygget, Bergen, 5020, Norway
Highlights of recent research from GEO:
13.00-13.15 Sebastian Wolf: Topography of mountain belts controlled by rheology and surface processes
13.15-13.30 Nele Meckler: Cenozoic evolution of deep ocean temperature from clumped isotope thermometry
13.30-13.45 Hasbi Ash Shiddiqi: Seismicity modulation due to hydrological loading in a stable continental region: a case study from Jektvik swarm sequence in Northern Norway
13.45-14.00 Desiree Roerdink: Emergence of felsic crust and subaerial weathering recorded in Palaeoarchaean barite
14.00-14.15 Gang Lu: Melt volume at Atlantic volcanic rifted margins controlled by depth-dependent extension and mantle temperature
14.15-14.30 Ritske Huismans: IODP Expedition 396 – Mid-Norwegian Continental Margin Magmatism and Cenozoic Climate
14.30-14.45 Thomas Theunissen: Mantle exhumation at magma-poor rifted margins controlled by frictional shear zones
14.45-15.00 Casey Nixon: Increasing fault slip rates within the Corinth Rift: A rapidly localising active rift fault network
15.00-15.15 Leonardo Muniz Pichel: Interplay between crustal-scale rift architecture and passive margin salt tectonics

Elco Luijendijk
2022-08-31 12:15 - 13:00
Reconstruction of the history of fluid flow in fault zones
Fluid flow, fluid pressure and water-rock interaction are important controls on fault activity. However, the relation between fluid flow and fault activity is often difficult to quantify because of a lack of data on the timing and duration of past flow events. In this presentation I will discuss a new approach to quantify the history of hydrothermal activity in fault zones that combines low-temperature thermochronology, borehole temperature data and numerical modelling. I will present case studies from the Basin and Range Province, the Alps and the Roer Valley Graben that provide new insights on episodic fluid flow and its links with deformation and seismic activity.

Gareth Hurman
2022-08-24 12:00 - 13:00
Quantitative analysis of faulting in the Danakil Depression Rift of Afar: the importance of faulting in the final stages of magma-rich rifting
Magmatic intrusion and faulting both accommodate crustal extension in magma-rich rifts. However, quantitative constraints on the contribution of faulting to total extension and detailed exploration of along-rift variations during the final stages of break-up are lacking. We targeted the Danakil Depression (Afar, Ethiopia) to conduct a quantitative, high resolution study of fault activity and interaction in a magma-rich rift close to break-up. Quantitative analysis of >600 rift axis faults, identified using remote sensing data, shows an increase in fault density, length and connectivity away from magmatic segments. Kinematic and earthquake focal mechanism data demonstrate a transition from transtensional opening in the northern and central sub-regions of the rift to oblique opening in the southern Giulietti Plain and Tat-Ali sub-regions. Oblique opening is attributed to the along axis step between the Erta-Ale and Harak sub-regions. Integration of seismic reflection and borehole data with the mapped faults shows that extension is primarily accommodated by magmatism within the rift centre, with faulting more significant towards the ends of the rift.
~30% of crustal extension is accommodated by faulting in areas of low magmatism, highlighting the importance of faulting even in the final stages magma-rich rifting.
Comparing our findings with spreading ridge morphology and structure, relevant due to the rift maturity and extensive magmatism, we conclude that the Danakil Depression is in a transitional stage between continental rifting and seafloor spreading. Spatial changes in the importance of faulting and magmatism in accommodating extension, alongside rift morphology, resemble the relationships observed along spreading ridges

Agustin Argüello Scotti
2022-08-10 12:00 - 13:00
Impact of Sedimentology in Multi-Scale Modelling of Fluvial Reservoirs For Enhanced Oil Recovery Projects (EOR): Case Studies in the Golfo San Jorge Basin
Agustín Argüello Scotti, Guillermo Pedersen, Florencia Schein, Héctor Campos, Marcio Armisen, Matías Mortaloni and Walter Brinkworth
Gerencia de proyectos estratégicos EOR; YPF S.A.; Macacha Güemes #515, CABA, Argentina
The use of enhanced oil recovery methods (EOR) is key to extend the life of mature oilfields in Argentina. The high investment they require however, calls for detailed studies and 3D modelling of the reservoir to provide for robust forecasts. The EOR Study group in YPF focuses a great deal of its efforts in the implementation of OER techniques in the fluvial reservoirs of the golfo San Jorge basin. The specific challenges of characterizing and modelling low net-to-gross fluvial reservoirs in this basin has encouraged sedimentological studies at different scales: semi-regional (field), block, pilot and detail. Although only the models of pilot and block scale may be dynamically simulated to reproduce the field history or provide forecasts, the studies and models at other scales provide very important information either incorporated in the simulation models or kept in consideration for uncertainty management. Information derived from sedimentological studies therefore, are a mayor consideration for building reservoir models and ultimately decision making.

Natalya Gomez
2022-05-18 12:15 - 13:00
Sea level, ice sheets and the solid Earth

This talk will focus on the physics of sea-level changes, glacial isostatic adjustment and solid Earth deformation following retreat of the polar ice sheets, and the implications of these changes on the past and future stability and dynamics of ice sheets and their contributions to sea level as climate changes.

Natalya Gomez
Associate Professor in Earth and Planetary Sciences
Canada Research Chair in Ice Sheet – Sea Level Interactions
McGill University
https://www.mcgill.ca/eps/gomez
natalya.gomez@mcgill.ca

Matteo Demurtas
2022-04-27 00:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Fracturing and force distribution during shearing in bimaterial gouges
Fault gouges are amongst the main products of strain accommodation in the brittle upper crust. During shear, fracturing has a direct effect on grain size (and shape) evolution and ultimately grain-grain interactions. Such changes are believed to influence how stress is accommodated within the gouge and therefore control the mechanical and petrophysical properties of granular materials. Recent observations of both natural and experimental strain localisation features have highlighted the potential for compositional anisotropy within a deforming rock to play a key role in control fracturing processes. As a result, the occurrence of a polyphasic mineral assemblage in natural gouges may strongly influence the rheology of a fault during deformation. Numerical simulations using the Discrete Element Method (DEM) approach have proved, in recent years, to be a powerful tool in revealing grain scale processes associated with frictional sliding of granular fault gouges. Such an approach affords us unusual access inside a deforming material to precisely track the active grain processes and how they interact and evolve. We performed DEM simulations designed to investigate the influence of a bimaterial mineral assemblage on fracturing, grain size distribution evolution, force and stress distribution within a deforming gouge applied to the carbonate system, with a calcite-dolomite mixture. Our simulations show how even small amounts (c. 20%) of a more competent phase can results already in significant changes in the fracturing processes occurring during shearing, ultimately bearing the potential of controlling its slip behaviour.

Åse Hestnes
2022-03-30 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Preliminary results from apatite thermochronology and U-Pb calcite geochronology – insight into the topographic evolution of Western Norway

Hestnes, Å.1, Jacobs, J.1, Drost, K.2, Dunkl, I.3, Gasser, D.4,5, Ksienzyk, A.K.5, Scheiber, T.4, Sømme, T.1,6, Mayer-Ullmann, F.1, Chew, D.2
1 Department of Geoscience, University of Bergen
2 Department of Geology, Trinity College Dublin, The University of Dublin
3 Sedimentology and Environmental Geology, Geoscience Centre, University of Göttingen
4 Department of Environmental Sciences, Western Norway University of Applied Sciences, Campus Sogndal
5 Geological Survey of Norway
6 Equinor, Oslo

By using apatite in thermochronological studies, we can unravel the cooling history, and thus potentially the erosion history of the uppermost continental crust (<120°C). We have collected an extensive dataset for thermochronological studies from Western Norway, located between the Sognefjorden in the south and the Møre Margin in the north. During Geolunch, I will present new results from both Apatite Fission Track (AFT) and (U-Th)/He apatite thermochronology. These data are combined to make time-temperature models, both for single samples and as a multi-model of a vertical profile. Such a multi-model of a vertical profile has not been done before in Norway and I will illustrate how it can be used as a tool to understand the topographic evolution of a region. In addition, I will show the results from the first U-Pb Calcite analyses done in Norway.

Prof Cathy Hollis
2022-03-23 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Limestones: an essential user guide to sediments that dissolve, precipitate and grow
Carbonate sedimentary rocks form through the accumulation of organisms and chemically precipitated calcium carbonate, usually on the sea floor. They preserve fragments of marine organisms, which are sensitive to temperature, salinity and seawater chemistry during their growth, and they therefore provide an exceptional record of evolutionary and climatic change through Earth history. Carbonate sediments are also highly reactive, dissolving and precipitating in surface water. For these reasons, despite their simple mineralogy, they have a reputation for being difficult to understand and many clastic sedimentologists approach them with caution!
Nevertheless, carbonate sedimentary rocks are important for many reasons. They have been exploited for millenia for their minerals, water resources and, more recently, for cement, roadstone and hydrocarbon. Now, as we face the effects of climate change, we can use carbonate strata to understand how Earth responds to environmental stress and use this knowledge to better predict the effect of climate change on modern ecosystems. There is also growing interest in how carbonate sedimentary rocks can be used to good effect for carbon storage and geothermal heat production. This talk will provide an introduction to carbonate sedimentology and the principle processes that govern their formation and modification during lithification. It will illustrate their importance to our modern landscape and heritage and demonstrate how ancient carbonate systems can hold warnings, and solutions, to the effects of anthropogenic environmental impact.

Professor Cathy Hollis
Chair of Carbonate Geoscience
The University of Manchester, UK

cathy.hollis@manchester.ac.uk
Cathy Hollis a geologist with a particular interest in low temperature fluid-rock reactions, geochemistry and petrophysics in sedimentary rocks. She is the research group lead for the Basins, Stratigraphy and Sedimentary Processes group in the Department of Earth and Environmental Science. She is also Adjunct Professor of Carbonate Geoscience at University of Bergen. Her work focuses on the origin, evolution and occlusion of porosity in carbonate strata utilising outcrop, subsurface core and geophysical data alongside geochemical proxies. She is particularly interested in how limestones react and transform to dolomite and how minerals precipitate and dissolve from fluids in sedimentary basins. Cathy is the principal investigator on a joint industry research consortium (PD3) with Universities of Bergen, Bristol and Liverpool, and collaborates with research groups in Canada, Qatar and France. She has extensive knowledge of the Lower Carboniferous Limestone of the UK, and she is leading a NERC funded project to assess the impact of hydrothermal karst on fluid flow. This work will be important to planning low-carbon, sustainable geothermal energy projects, which will be an essential part of our transition to net zero. Cathy has published over 45 papers in international, peer-reviewed journals in the last 10 years and graduated more than 15 PhD candidates in that time. She has a PhD from University of Aberdeen and prior to joining University of Manchester, in 2007, she worked for Badley Ashton and Associates Ltd in the UK and UAE (1995-2001) and Shell International Exploration and Production in The Netherlands (2001-2007).

Flávio Norberto de Almeida Junior
2022-02-23 12:00 - 13:00
Hyperpycnal flows: are they sediment-gravity flows?
Authors: Flávio N. de Almeida Júnior & Ronald Steel
Hyperpycnal flow is a process involving the underflow of denser material through sediment-laden river currents that enter lighter ambient water, e.g., lake or seawater. Relatively high suspended sediment concentration in the river flow is often the main cause of the high flow density forcing the river-discharge to plunge in the area of the river mouth. Sediment particles make hyperpycnal flows denser than the water they displace, otherwise fresh water would be lighter than seawater, so that many authors ubiquitously consider hyperpycnal flow as a type of sediment-gravity flow. Hyperpycnal flow models also idealize a hydraulic continuum between the fluvial current and the plunging of hyperpycnal flow, in the notion that hyperpycnal flow discharges beyond the river mouth into ambient water would have velocity profiles and duration approximate to the parental river currents.
However, recent studies show that : (i) the initiation of underflows may occur from extremely dilute river plumes so that any defined value of threshold sediment-concentration is not enough to explain the plunging of river discharges – thus, the notion of denser does not directly equate to excess of sediment-mass (volume x density) or sediment gravity transport in the flow; (ii) not all energy fluctuations in hyperpycnal flows are necessarily a function of river hydrography; and (iii) large-magnitude river floods do not necessarily imply high sediment concentration or hyperpycnal flows, and not all sediment-gravity currents generated during river-flood periods must necessarily be of hyperpycnal origin (e.g., slope collapse at Squamish Delta during river flood periods). All the above constraints are allusive: fluid mechanics of hyperpycnal flows are mired in controversy, and there has been a fuzzy use of the term ‘hyperpycnal flow’ since its early definition – in particular regarding the connection between river dynamics and hyperpycnal flows. Hence, there is still uncertainty on how to recognize the deposits of hyperpycnal flows in the sedimentary record.
This presentation aims to bridge between hydrodynamic processes and the deposits of riverine hyperpycnal flows by critically analyzing what is known-to-date from experiments, modern environments and the empirical evidence. We therefore propose a novel classification for hyperpycnal-flows based on the concept of discharge momentum, in which initial conditions of discharge momentum at river flow unconfinement and its subsequent dissipation into ambient water would primarily constrain hyperpycnal flow parameters. This approach allowed distinction of three hyperpycnal-flow types, which not all actually represent sediment-gravity flows. For the first time, we provide a simple resolution that links river-discharge hydrodynamics to hyperpycnal flows that can be used as diagnostic criterion for the identification of hyperpycnal-flow deposits (or hypepycnites) on strata. We support our arguments with published literature and new diagnostic field data from the Early-Middle Jurassic Lajas and Los Molles formations in the southernmost Neuquén Basin, Argentina.

Vincent Wicker
2022-02-16 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Transition from Aegean back-arc extension to Corinth rifting. Miocene to Pleistocene interacting extensional regimes of the Northern Peloponnese.
Vincent Wicker1, Mary Ford1, Robert Gawthorpe2, Haralambos Kranis3, Emmanuel Skourtsos3, Pierre Bouilhol1, Martin Muravchik2, Natacha Fabregas2, Kévin Beaufumé4, Hugo Beldame5
1 – University of Lorraine, CRPG-CNRS, Nancy, France; 2 – University of Bergen, Norway; 3 – National and Kapodistrian University of Athens, Greece; 4 – Perenco, UK; 5 – ENSG Nancy, University of Lorraine, France
Continental extension is characterized by two end members: rifting and highly extended terrains. These two modes of extension usually develop under very different conditions and are rarely observed together. However, in the northern Peloponnese, metamorphic windows recording Miocene late orogenic to back arc extension of the Southern Hellenides on low angle detachments, lie directly south of the younger Pliocene-Pleistocene Corinth rift and appear to interact with its southern margin fault system. This work integrates data from a recent structural and stratigraphic field campaign from the Central Peloponnese to the Corinth rift southern margin with regional cross-sections to document the style of regional Miocene to Pliocene extensional tectonics and the transition from the wide extensional regime to the narrow Corinth rifting. It shows that the pre-rift Hellenides nappe stack was stretched by about 15-25 km by low angle extensional faults that root into the Cretan detachment that forms the main decoupling level in this area. These low-angle extensional faults contribute to the exhumation of the Quartzite-Phyllite metamorphic nappe and contribute to the continental unroofing of the Southern Hellenides. New field data in the northern Peloponnese indicate that continental sedimentation controlled by these low angle normal faults underlies in apparent continuity the Corinth syn-rift succession, which is itself controlled by later high angle rift faults. We integrate in a regional structural model the transition from the pre-rift Aegean extensional tectonic regime to early-stage Corinth rifting recorded in newly mapped depocenters located in the south-eastern Corinth basin between Stymfalia and Nemea.

Gang Lu
2021-12-01 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Magmatism at Atlantic volcanic rifted margins: When do we need mantle plumes?
Breakup volcanism along rifted passive margins is highly variable in time and space. The factors controlling magmatic activity during continental rifting and breakup are not resolved and controversial. Here we use numerical models to investigate melt generation at rifted margins with contrasting rifting styles corresponding to those observed in natural systems. Our results demonstrate a surprising correlation of enhanced magmatism with margin width. This relationship is explained by depth-dependent extension, during which the lithospheric mantle ruptures earlier than the crust, and is confirmed by a semi-analytical prediction of melt volume over margin width. The results presented here show that the effect of increased mantle temperature at wide volcanic margins is likely over-estimated, and demonstrate that the large volumes of magmatism at volcanic rifted margin can be explained by depth- dependent extension and very moderate excess mantle potential temperature in the order of 50–80 °C, significantly smaller than previously suggested.

Enry Horas Sihombing
2021-11-17 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Form And Fill of A Transtensional Lacustrine Rift Basin: Lower Talangakar Formation, Jatibarang Subbasin, Offshore NW Java, Indonesia

Felix Halpaap
2021-11-10 12:00 - 13:00 | Geomorphology room 3F14, allegaten 41, Bergen, 5020, Norway
Tracing tectonically active faults with the smallest earthquakes:​ sensitive detection of the 2021 Bitdalsvatnet earthquake swarm​

Thomas Theunissen
2021-11-03 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Topography during Pangea Breakup – Case of the South Atlantic Central Segment – 2-D thermo-mechanical modelling and implications for salt basin formation

In this study we use observations from the central South Atlantic conjugate margins to constrain
the structural style of rifting and its relation with sedimentary basin evolution during
the syn and early post-rift. Three synthetics transects from North (Gabon-Brazil) to South
(Angola-Brazil) are used to constrain fault distribution, margin width, crustal thickness,
distribution of magmatism, syn-rift sedimentary section thickness and paleo-environment
from the start of rifting in the Berriasian (145 Ma) until the early post rift in the Aptian (114 Ma).
This integrated study aims to understand variations in along strike structural style,
magmatic output, and sedimentary basin evolution to assess the contribution of
mantle processes on topography using forward 2-D thermo-mechanical modelling.
We design a model setup that reproduces South Atlantic central segment main characteristics
before rifting. We then explore the effect of sedimentation rate on subsidence and the effect of
mantle temperature on topography. The model accounts for decompression melting with feedbacks
on temperature, viscosity and density of the mantle. The subsidence in the thermo-mechanical
models is calibrated with a reference mid-ocean ridge elevation, where a 6 km thick oceanic crust
is predicted, and explained by the different contributions on buoyancy of rifted passive
margin during rifting. We discuss conditions to get magma-poor margins and conditions
to reach a small topographic gradient and shallow water environment between the proximal
and distal domains over more than 200 km of the wide margin during most of the syn-rift.

Gang Lu
2021-10-29 12:00 - 13:00 | Geomorphology room 3F14, allegaten 41, Bergen, 5020, Norway
Potential temperature and depth-dependent extension control melt volume at Atlantic volcanic margins
Breakup volcanism along rifted passive margins is highly variable in time and space. The
factors controlling magmatic activity during continental rifting and breakup are not resolved
and controversial. Here we use numerical models to investigate melt generation at rifted
margins with contrasting rifting styles corresponding to those observed in natural systems.
Our results demonstrate a surprising correlation of enhanced magmatism with margin width.
This relationship is explained by depth-dependent extension, during which the lithospheric
mantle ruptures earlier than the crust, and is confirmed by a semi-analytical prediction of
melt volume over margin width. The results presented here show that the effect of increased
mantle temperature at wide volcanic margins is likely over-estimated, and demonstrate that
the large volumes of magmatism at volcanic rifted margin can be explained by depthdependent
extension and very moderate excess mantle potential temperature in the order of
50–80 °C, significantly smaller than previously suggested.

Ritske Huismans
2021-10-27 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Preliminary results from IODP Expedition 396 – Mid Norwegian Continental Margin Magmatism

Irfan Baig
2021-10-20 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Quaternary basin fill and evolution of the North Sea Basin: A synthesis of sequence stratigraphy and basin modeling techniques
by Baig, Irfan; Faleide, Jan Inge; Aagaard, Per; Chuahan, Teena; Hjelstuen, Berit Oline Blihovde & Sejrup, Hans Petter

Lucas Valore
2021-10-06 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Large Igneous Provinces, hydrovolcanism and paleoenvironments/paleohydrology: lessons from the Paraná Basin in South Brazil
In many continental flood basalt provinces (CFBPs), primary mafic volcaniclastic deposits have been shown to be significant counterparts of better-known effusive (lava flow) facies, a notion that challenged traditional views of CFB stratigraphy some decades ago. Many of such deposits have been linked to hydrovolcanic phenomena, which are basically all sorts of magma – water interaction that induce magma fragmentation and create specific types of volcaniclastic deposits. At the time, some studies linked this to how LIPs have been able to induce massive extinctions in the geological record. Until the early 2000s, one of the only exceptions to this was the Paraná Igneous Province in South America, where the enormous amounts of lavas from the so-called Serra Geral Group were emplaced above a seemingly completely arid paleoerg (Botucatu). However, this was later shown to not be entirely true, as during syn-volcanic times multiple types of humid environments have been recorded – many have been responsible for the repeated formation of peperites, a volcanic breccia with sedimentary matrix that in this case is formed as lava flows invade bodies of humid sediment. Further studies have shown that other hydrovolcanic deposits also exist in Paraná, although this has stirred a lot of controversy. These include pillow lavas, hydrothermal injectites and pyroclastic rocks – the latter, which were my main focus during my master’s, will be the main subject of the talk. Ultimately, detailed mapping of these facies show that they are far from being the exception, and that perhaps the volcanic activity is somehow linked to this change in paleoenvironmental conditions.

Leonardo Pichel
2021-09-17 12:00 - 13:00 | Kvartsitten, 3rd floor, Realfalbygget, Bergen, 5020, Norway
Coupling crustal-scale rift architecture with rifted margin salt tectonics: a geodynamic modelling approach
Many rifted passive margins are associated with widespread and thick evaporite (i.e., salt) deposits, and pronounced syn-and post-rift salt tectonics. The majority and largest salt basins known-to-date formed during the latest stages of rifting, immediately prior to continental breakup. We use 2D thermo-mechanically coupled finite-element modelling of lithospheric extension to investigate the interplay between variable styles of rifted margin, syn-rift architecture, and consequences for distribution of late syn-rift salt, and post-rift salt tectonics. We simulate the formation of salt basins in different types of continental margins: narrow, intermediate, wide, and ultra-wide margins. For each of these we evaluate: 1) the interplay between rifting, post rift sediment progradation, base-salt topography and margin scale salt tectonics, 2) the spatial and temporal distribution of salt-related structural domains, and 3) the contrasting styles of salt tectonics for different margin types. We show that narrow and intermediate margins form partially isolated salt basins in their proximal domain with limited translation and significant vertical diapirism. Their distal portions are associated with significant translation, development of updip listric normal faults and rollovers passing downdip to squeezed diapirs. Wide and ultra-wide margins form wide salt basins with a more subtle base-salt topography which result in significant salt expulsion and overburden translation towards their distal domains. These margins are characterized by updip extensional and/or expulsion rollovers and downdip salt inflation, diapirism and shortening in the form of diapir squeezing, buckle-folding and development of allochthonous salt sheets. All margins present a distal salt nappe that forms by a combination early rift-related stretching and post-rift thrusting. The nappes vary in width and magnitude of deformation according to each each margin type. These models are the first to integrate lithospheric extension with long-lived post-rift salt tectonics using a geodynamically self-consistent modelling approach where the geometries of the lithosphere and salt basins are not prescribed, allowing a natural evolution of syn and post-rift deformation. They also incorporate a more realistic style of post-rift progradation using a dynamically evolving profile and present unprecedent detail for salt, syn- and post-rift stratigraphy. The results can be directly compared to examples from various salt-bearing continental margins and provide an improved understanding on the kinematics and relative timing of rift and salt deformation, and on the controls and variability of salt tectonics for different margin types.

Flávio Norberto de Almeida Junior, Felix Halpaap: Field trip reports
2021-09-03 00:00 - 13:00 | Kvartsitten, 3rd floor, Realfalbygget, Bergen, 5020, Norway
“Geology fieldwork in the High Arctic – some pictures taken during the 2021 Sequence Stratigraphy course on Svalbard”
By Flávio Norberto de Almeida Junior

“Picture report from new remote seismic stations on Svalbard – how we worked against fog, ice, and time to get the 1st station north of 80º in Norway up & running”
By Felix Halpaap

Matteo Demurtas
2021-06-02 12:15 - 13:00
Faulting at near-surface conditions: an example from unconsolidated deposits in the Central Apennines

Natacha Fabregas
2021-05-26 12:15 - 13:00
Deep-water syn-rift sedimentary response to alternating Late Quaternary palaeoenvironments in the Gulf of Corinth (Greece)
Relatively few detailed studies exist of rift axis depositional systems and the controls on their sedimentology and stratigraphy. Cores from the IODP Expedition 381 (Corinth Active Rift Development) provide a continuous high resolution stratigraphic record of depositional processes operating within this deep-water rift. During the Late Quaternary, the Gulf of Corinth alternated between marine and isolated/non-marine conditions due to intermittent connection with the open ocean across a sill driven by climate-related sea-level fluctuations. In this study we performed bed scale logging of the sedimentary deposits within the eastern Gulf of Corinth in order to understand key controls on sedimentation during the Late Quaternary. High resolution, mm-scale analysis was performed on the first 300 m of core from Site M0079 that records the last two glacial-interglacial cycles and the Holocene (Marine Isotope Stages 1 to 7). The succession is dominated by fine-grained gravity flows (event beds) and hemipelagic sediments. Event beds result from discrete events that interrupt/overprint ongoing low energy sedimentation. As such, these have been abstracted in order to define three main sedimentary unit types. Unit-scale logging was extended to the rest of the succession and to the other drill sites to build a stratigraphic and depositional model covering the last ca. 700 kyr of deposition. Our results show that during interglacial periods (i.e. marine conditions), the sediment record consists mainly of highly bioturbated mud with rarer occurrences of coarser grained sediment. Sedimentary structures and identifiable event beds have largely been lost due to the high degree of bioturbation. In contrast, during glacial periods (i.e. isolated/semi-isolated lake conditions) the deposits are well bedded with a low bioturbation index and background muds alternate with event beds. Transitional strata, between marine and non-marine units, show finely laminated beds rich in aragonite, often becoming more organic rich toward the top. The deepest parts of the core penetrate slumped units and thicker gravity flow deposits. This study allows us to recognise the response to high frequency climatic fluctuations recorded in the sedimentary succession of this deep-water rift.

Stéphane Rondenay
2021-05-12 12:15 - 13:00
What causes volcanic gaps in subduction zones? Insights from South central Alaska

Kristian Jensen
2021-05-05 12:15 - 13:00
Improving modelling of seismic images through Point-Spread Function-based convolution
Seismic images are generated when a source at the Earth’s surface initiates a pressure wave which travels through the Earth’s subsurface. As the wave hits layer boundaries in the Earth’s interior, energy is reflected back to the Earth’s surface where it is recorded, thus allowing us to obtain an image of the subsurface. The principle behind this approach is exactly the same as in medical ultrasound.
Due to the complexity of the Earth, and the intricate wave physics involved, the raw seismic images usually contain many distortions and artefacts. As such, extensive processing is often needed to obtain proper images of the subsurface. Yet, even after performing a processing workflow, features in the images may still be ambiguous and difficult to identify.
In order to study in greater detail exactly what seismic images will look like for a certain geological setting and survey geometry, seismic modelling may be performed. This involves using a computer to generate a model of the subsurface, and then simulating what the seismic images will look like for a given survey geometry over the model. Proper seismic modelling can be very helpful in identifying exactly why ambiguities occur, and what may be done to improve the quality of the images.
Seismic modelling approaches are, however, often computationally expensive. The aim of my PhD is therefore to further develop a method which may perform accurate seismic modelling at a low computational cost. The method estimates the local illumination and resolution at specified points in the model, referred to as point-spread functions (PSFs). The PSFs are computed by tracing the path of the wave through the Earth (a procedure referred to as ray tracing), and not through a full simulation of the wave equation. This allows for a very quick estimation of the PSFs. The PSFs may then be mathematically convolved with the Earth model in order to simulate a processed seismic image. Through this method we can quickly and efficiently study how survey geometry, seismic wave velocity, frequency bandwidth and amplitude effects influence the quality of the seismic image surrounding the point of interest. However, as the method does not solve the full wave equation, some simplifications and limitations exist. My PhD-project therefore aims to improve the quality of the modelled seismic images by attempting to overcome some of the inherent limitations while retaining the low computational cost.
Illustration of how changes in seismic modelling parameters yield different seismic images of the same target area. Foto/ill.: Kristian Jensen, UiB

Felix Halpaap
2021-04-16 14:00 - 15:00
Leveraging seismic data quality metrics for network supervision and sensitive earthquake detection

In earthquake seismology, the last decade has led to ever growing datasets of continuous seismograms being recorded, stored, and made openly available. These ever increasing datasets (e.g., about 50 M hours of seismograms or 17 TB for Norwegian networks alone) allow us to revisit the data with new methodologies, for example by template matching to detect previously uncataloged earthquakes. Template matching is based on correlatiing known earthquake waveforms against continous seismic data to detect similar and helps to obtain more complete catalogs of seismicity that are suited for further statistical analysis. One challenge in applying template matching to larger datasets is that one needs to be able to sysematically recognize problems in data quality that quickly lead to misdetections. What helps with this task are seismic data quality metrics – a set of up to 50 measures of specific data properties for each day and trace – for which two major systems now exist. In this talk, I will introduce how these data quality metrics help us to (a) keep better control of data quality in archived data, (b) monitor the state of the currently recording stations systematically, (c) apply sensitive template-matching without misdetections (with examples from the North Sea and a Norwegian reservoir), and (d) gain a new overview of seismic noise throughout the network operations.
