Vincent Wicker
2022-02-16 12:00 - 13:00 (Europe/Oslo) | 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.

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.

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).

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.

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.

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

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.

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

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.

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

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.

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.

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.

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

Simone Masoch (Dipartimento di Geoscienze, Università degli Studi di Padova, Padua, Italy)
2022-11-02 12:00 - 13:00
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.

Grace Shephard
2022-11-09 12:00 - 13:00
s-Inking the rainbow – introducing two initiatives for generating better science graphics
Grace Shephard
The adage, “a picture is worth a thousand words,” is wholly applicable to the (geo)sciences. Whether in publications, talks, teaching or press-releases, the use of effective graphics is paramount to progressing science and maximising cross-overs with society. However, several obstacles threaten this trajectory. A first hurdle might be where to find up-to-date science graphics that are not under copyright. The next may be through the use of rainbow colour scale like “jet” (spoiler alert: the error that the rainbow introduces is quantifiable). Another is propagation of an eye-catching figure that nevertheless shows a scientifically-inaccurate or misleading process. In this lunch time talk, I will introduce two bottom-up initiatives to make and share better graphics (s-Ink.org and Scientific Colour Maps), and encourage you to be a part of them too.

Dr Grace Shephard is a Researcher at the Centre for Earth Evolution and Dynamics (CEED) at the University of Oslo. She received her PhD from the EarthByte Group at the University of Sydney. Her research interests include plate tectonics and mantle dynamics, and has a particular interest in development of the North Atlantic and the Arctic. She received a NFR YFF grant for her project “POLARIS – the evolution of the Arctic in deep time” (2021-2025).

Ujjwal Shekhar
2022-11-16 12:00 - 13:00
Ujjwal Shekhar
Microseismic wavefield modeling using the integral equation method
Induced seismicity is commonly associated with activities like conventional and unconventional oil/gas production, enhanced geothermal systems, carbon sequestration, hydraulic fracturing, etc. Fluid injection/extraction affects the pore pressure within the rockmass and may lead to the reactivation of critically stressed pre-existing faults. Seismic waves are generated at a source that can be associated with a slip on the fault plane. These microseismic events are often considered weak seismic events. However, in the past few years, the occurrence of moderate to strong earthquakes induced by fluid injection (as an example, a magnitude 5.8 earthquake on September 23, 2016 in central Oklahoma: source – USGS) has posed a threat that cannot be overlooked.
Microseismic wavefield modeling is one of the key aspects of a microseismic monitoring project. Microseismic monitoring is a passive technique that involves analyzing the seismic data gathered over the region of interest to detect such events. It is necessary to characterize and locate microseismic sources in order to avoid any risk of environmental hazards and damage to the infrastructures. The main goal of this work is to demonstrate seismic wave propagation in elastic media due to different types of microseismic sources. Using the fundamentals of scattering theory, the elastodynamic wave equation is formulated as an integral equation of the Lippmann-Schwinger type. The Fourier transform-based iterative solver is implemented to obtain the wavefield in an efficient way. The numerical scheme is applied to anisotropic and heterogeneous models with the purpose of investigating the applicability of the method in complicated geological scenarios.

Umut Isikalp
2022-11-23 12:00 - 13:00
Sedimentology and Stratigraphy of the Cambrian and Ordovician Deposits in SE Turkey
Umut Isikalp

BSRG practice - Agustin, Lucas and Melanie
2022-11-30 12:00 - 13:00
The British Sedimentological Research Group 2022

Agustin Argüello Scotti
Lucas Albanese Value
Melanie Kling

Titles/abstracts coming soon…

AGU 2022 practice
2022-12-07 12:00 - 13:00
Thomas Theunissen – Oblique continental rifting. Insights from 3-D forward geodynamic modelling coupled with surface processes and application to the Equatorial passive margins formation.
Sebastian Wolf – How high do mountains grow? quantifying growth and decay of topography in collision orogens
Björn Johan Emil Burr Nyberg – Global Scale Analysis on the Geomorphology of Rivers and Channel Belts

Thomas Theunissen – Oblique continental rifting. Insights from 3-D forward geodynamic modelling coupled with surface processes and application to the Equatorial passive margins formation.
Plate divergence (continental rifting) is often oblique to the rift axis or plate boundary, comprising many active rifts and mature rifted margins on Earth. Recent findings from field-based studies, plate reconstructions and numerical and analog models suggest that rift obliquity plays a critical role in rift evolution and imparts fundamental controls on the eventual architecture of mid-ocean ridges and mature rifted margins. These studies show the importance of vertical strike-slip and transform structures in the oblique extension process but also reveal that the initiation of syn-rift vertical strike-slip motion over long distances requires inherited weaknesses. As a typical example the Southern part of the Equatorial passive rifted conjugate margins exhibit segments with different tectonics and subsidence histories alternating with transform segment with different lengths and orientation. We aim in this study 1) to evaluate the role of the inheritance (obliquity, geometry of weaknesses) in controlling the pattern of faulting (type of fault, direction of propagation, and linkage), and 2) to evaluate the feedback between tectonics and surface processes in this context to understand consequences on landscape evolution. For this purpose, we use most recent advances in 3-D forward geodynamic modeling coupled with surface processes. Preliminary results confirm the importance of inheritance in shaping the continental rift by controlling fault propagation leading to oblique segments with variable tectonics and subsidence history and show some unexpected feedbacks between tectonics and surface processes. These results compare well to the Equatorial system and provide important insight on the causes that might explain timing and amplitude of vertical motions and related sediment flux.
Björn Nyberg – Global Scale Analysis on the Geomorphology of Rivers and Channel Belts
Rivers are fundamental geomorphic features on the Earth’s surface and have an important role in controlling human habitat, climate, ecosystems, and the hydrological cycle. However, only recently has the surface area of rivers globally been quantified, and there remains a significant knowledge gap in understanding the distribution of river types, the extent of channel belt deposits and their morphology. Yet it is these factors that ultimately control the behavior of river systems and the ecosystems and human livelihoods that depend on those rivers. Here we develop a novel machine learning method to recognize the patterns of different river channels and their deposits to classify their morphology. Our results quantify, for the first time, that the global observable extent of river channel belts covers an area of 30.5 x 105 km2, which equates to roughly the known size of lakes or 7 times larger than the extent of river channels. Of those channel belts, nearly 77% of the surface area are classified as meandering with the remainder defined by a more braided morphology. Furthermore, we quantify the hydrological, physio-climatic and tectonic controls governing the geomorphology of rivers globally. It is hoped that the new Global River Morphology (GRM) map and database may provide new insights into predicting the intensity and behavior of future floods, improve analysis of biogeochemical cycles and aid in water resource management
Sebastian Wolf – How high do mountains grow – quantifying growth and decay of topography in collisional orogens
How does a collisional mountain belt grow and decay? It is widely recognized that crustal thickening creates topography, while river incision counteracts orogenic growth and leads to topographic decay, thus providing a link between climate, surface processes and tectonics. However, it remains uncertain whether surface processes or lithospheric strength control mountain belt height, width, and longevity, reconciling high erosion rates observed for instance in Taiwan and New Zealand, low erosion rates in the Tibetan and Andean plateaus, and long-term survival of mountain belts for several 100s of million years. Here we use a tight coupling between a landscape evolution model (FastScape) and a thermo-mechanically coupled mantle-scale tectonic model (Fantom) to investigate mountain belt growth and decay. Using several end-member models and introducing the new non-dimensional Beaumont number, Bm, we quantify how surface processes and tectonics control mountain growth and define three end-member types of growing orogens: Type 1, non-steady state, strength controlled (Bm > 0.5); Type 2, flux steady state, strength controlled (Bm ≈ 0.4−0.5); and Type 3, flux steady state, erosion controlled (Bm < 0.4). Bm can be assessed without complex measurements or assumptions, but simply by knowing a mountain belt’s convergence rate, height, width, first order shortening distribution, and widening rate. Applying our results to several orogens on Earth indicates that tectonics dominate in the Central Andes and Himalaya-Tibet (both Type 1), efficient surface processes balance high convergence rates in Taiwan (Type 2), and surface processes dominate in the Southern Alps of New Zealand (Type 3). Quantifying orogenic decay, we find that removal of topography is primarily determined by erosional efficiency and can be subdivided into two phases with variable isostatic rebound characteristics and associated timescales: First short-wavelength relief is removed within a few Myr, followed by removal of long-wavelength topography and effectively local isostatic rebound. Our results provide a simple unifying framework quantifying how surface processes and tectonics control the shape, height, and longevity of mountain belts on Earth.

Ingrid Kristine Jacobsen & Omar Yesid Duran Triana
2023-01-11 12:00 - 13:00
Ingrid Kristine Jacobsen (and here)– abstract:

Exploitation of energy from enhanced geothermal systems is performed by injecting fluid at high pressure into the reservoir such that faults are deliberately opened. The fault opening causes enhancement of the fluid flow, which is favorable for exploitation of the geothermal energy, but also fault slip, which may be of the unstable kind that results in induced seismicity.
In this talk I will first present a mathematical model for fault deformation in a mixed-dimensional setting. Then I will move on to talk about the concepts behind the rate and state friction (RSF) models which are widely used in simulations regarding seismicity. Briefly explained, RSF models consider the coefficient of friction to be dependent on both slip rate and the state of the contacting rock surfaces, and parameters appearing in its model equations can tell us about whether fault slip will be unstable (seismic) or stable (aseismic).

Omar Yesid Duran Triana (and here)- abstract:
This research was inspired and intended as an extension to the mixed-dimensional poromechanical models for fractured media presented in [1]. There the classical continuum mechanics is considered in the context of finite and infinitesimal strain. We addressed fracture mechanics from a different perspective by considering the linear theory of the Cosserat (micropolar, asymmetric) continuum. We considered an conforming-H1 method for the resulting set equations. Extra regularity can be achieved on the asymmetric component of the stress tensor and fracture tractions through the angular momentum balance defined on surfaces. We addressed the second-order formulation and present numerical results for the adopted model.
[1] W.-M. Boon and J.-M. Nordbotten. Mixed-dimensional poromechanical models of fractured porous media. Acta Mech (2022).

Melanie Kling
2023-01-18 12:00 - 13:00
Response of a clastic source-to-sink system to extreme environmental perturbations: the Permian-Triassic transition on Finnmark Platform, Barents Sea
Melanie Kling
The eruption of the Siberian Traps at the Permian-Triassic transition significantly affected depositional environments world-wide. Known consequences are (I) extreme global warming, (II) increased soil-erosion, decreasing chemical weathering and aridification on the continents, (III) oceanic stagnation and acidification, and (IV) the most severe mass extinction on Earth. In the Southwestern Barents Sea, the record across the Permian transition is continuous at a cored site located close to the basin margin, making it possible to study the response of a relatively proximal source-to-sink system in terms of petrography, provenance, and sedimentary environments. The record consists of Upper Permian carbonates developed as an oxygenated carbonate platform, overlain by transitional dys- or anoxic, organic-rich shales and a Lower Triassic prograding siliciclastic turbidite-prodelta-delta system.
In this project we use these deposits to reconstruct the sediment source area and changes within the catchment area across the Permian-Triassic transition. From a dataset of >50 2D seismic lines and sampled sandstones from ~160 m stratigraphic cores, we have already found that the sediment supply rate increased by more than 100-fold, which vastly exceeds the world-wide trend of sediment supply increase across the Permian-Triassic transition (6–7-fold). This has led to several models that may explain the observed evolution, but in order to distinguish between these models, mudstone provenance and weathering proxies must also be investigated. Herein we focus on the Neodymium and Hafnium isotopic composition in the mudstones, and thus present insights into weathering processes. This will allow us to investigate the climatic component in the catchment across the transition. Our preliminary results show that the catchment in the Late Permian supplied mudstones with extreme (much more than observed in modern deposits) chemical weathering and a stable provenance from a small, nearshore catchment. Broadly coincident with the Permian Triassic Transition, mudstones show a provenance change consistent with increase in catchment area and a strong decrease in chemical weathering. This indicates that the increase in sediment supply from at the Permian-Triassic transition was not caused by sudden flushing of onshore weathered material stored in catchments during the Permian, nor can it be caused by increase in chemical weathering because of climate change. It appears that the observed changes are mainly a result of tectonic uplift and tilting of Northern Fennoscandia possibly due to onset of a new rifting episode in the Norwegian-Greenland Sea. The coincidence of this strong response to the Permian-Triassic transition could perhaps indicate that adjustments of the catchment to the new topographic setting was helped by the climate change.

Martin Kjenes
2023-01-25 12:00 - 13:00
Martin Kjenes
coming soon…

Albina Gilmullina
2023-02-01 00:00 - 13:00
Albina Gilmullina
coming soon…

Helene Stemland
2023-02-08 00:00 - 13:00
Helene Stemland
coming soon…

James Opemipo Olomo
2023-02-15 12:00 - 13:00
Along strike variability of structural style and evolution of the South Viking Graben and western flank of the Utsira High
James Opemipo Olomo

Mads Jelby
2023-02-22 12:00 - 13:00
Far from home: Facies architecture of distal delta wedges across a wide ramp (Lower Cretaceous, Svalbard)
Mads E. Jelby

Anne Imig
2023-03-01 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Assessing managed aquifer recharge as a sustainable measure for groundwater management – An application for Grand Bahama
Anne Imig
A large storm surge caused by Hurricane Dorian in 2019 resulted in saltwater intrusion into the aquifers of Grand Bahama Island. This caused 40% of the island’s water supply to become brackish with no or slow recovery to date. Managed aquifer recharge (MAR) is investigated as a nature-based solutions to mitigate the impacts of Hurricane Dorian. First, a technical assessment of MAR investigates (hydro-) geological aspects. As a result, potential locations for a MAR scheme are proposed. Further, a financial and an extended cost-benefit analysis (CBA) integrating ecosystem services (ES) assessments are conducted for proposed MAR measures. Based on the current data availability, results indicate that the MAR scheme is technically feasible. However, it will not be able to provide the water demand and is not favorable from a financial perspective in comparison to a desalinization plant. The results of this study proofs the technical feasibility and the added value of restoring the groundwater ecosystem on Grand Bahama, but also highlight that high costs are connected with it. Due to the high costs the added value should be reevaluated and further data should be collected to support the findings.

Enry Horas Sihombing
2023-03-08 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Geomorphology of normal fault footwalls and fault scarps: Greater Tampen Spur Area, northern North Sea
Enry Horas Sihombing
Late Jurassic rifting in the Greater Tampen Spur area created a network of major normal faults, the footwall crests and fault scarps of which show major variations in their geomorphology. In this study we characterise this variable footwall geomorphology using a ~3700 km2 3D PSDM seismic volume and several key wells from the Snorre and Visund fault blocks. Our objectives are to: (1) document the different geomorphic characteristics of major footwall blocks; (2) illustrate the variable geomorphology of fault-controlled scarps; 3) define the syn- and early post-rift depositional systems in the immediate hanging walls of major normal faults and their relationships to the geomorphology of the adjacent footwalls; and 4) understand the tectonic, stratigraphic and surface processes responsible for developing varied footwall and fault scarp geomorphology. Visund and Snorre footwall blocks exhibits differing styles of footwall crest shape and internal morphology. The Snorre fault footwall has a broad, 10-14 km wide and 60 km long, gently west-dipping plateau whereas the Visund fault footwall has a curved convex-up, east-dipping, nearly 50 km long and 6-8 km wide crest in cross section which gives way to a westward facing dip-slope. The fault scarps associated with the Snorre, and Visund fault blocks host collapsed and rider blocks of different stages of maturity, mass wasting complexes and canyon systems. Rider blocks and fault scarp collapse structures are most common along the Snorre fault zone and are located at the point of maximum fault displacement (3-5 km throw). In areas of lower displacement, both fault blocks exhibit canyon systems along their southern extents, with canyons 1-2 km in width and <0.5 km deep. Canyons are consistently observed where the footwall and fault scarp host the Late Trassic Lunde Formation in the subcrop of the Base Cretaceous Unconformity (BCU). The variability of fault scarps may be controlled by interactions of mechanical strength of pre-rift stratigraphy and the tectonic setting and evolution. Along-strike and temporal variability in displacement along the fault segments would also produce differing uplift histories along, and between fault segments. Furthermore, strain migration towards the rift axis is interpreted to produce different depositional environments (a subaerially exposed Snorre footwall and largely subaqueous Visund footwall) during much of the Late Jurassic, which likely created different erosion potential and geomorphic responses between the two fault blocks. The study highlights the importance of integrating both local and regional tectono-sedimentary factors when characterising the highly variable character of fault scarp degradation.

Kui Xang
2023-03-15 12:15 - 13:00
Non-linear inverse scattering in anisotropic elastic media using a modified Born iterative method
Kui Xang
Estimating an accurate subsurface model of the Earth is crucial for identifying the locations of reservoirs. With the development of long offsets and wide azimuth seismic data acquisition, we can extract multiple anisotropic parameters from the recorded data to describe the right physical features of the Earth’s subsurface. Recently, we present an iterative non-linear inverse scattering algorithm for the reconstruction of the elastic parameters and mass density. To solve the non-linear forward scattering problem, we transform the elastodynamic wave equation into an integral equation, and then solve that integral equation by a fast-Fourier-transform-accelerated Krylov space method. For the non-linear inverse scattering problem, we approximate it to a series of linear approximations by using the Born approximation. Then, we use a modified Born iterative method to invert the model update at each linear approximation. The modified Born iterative method is based on the explicit computation of the Fréchet derivative. In our algorithm, the Fréchet derivative and its adjoint operators are presented in matrix-free manners so that we can also use the fast Fourier transform to reduce the computational cost and memory demand. We formulate the multi-parameter non-linear inverse scattering problem using a modified matrix-free Born iterative method. The application of synthetic data examples demonstrates its capability to produce accurate inversion results.
