Bjarne S G Almqvist

Bjarne S G Almqvist
Uppsala University | UU · Department of Earth Sciences

PhD

About

138
Publications
24,034
Reads
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1,204
Citations
Citations since 2016
76 Research Items
1019 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Introduction
My interests are in how physical properties of rocks and minerals reflect the chemical and deformation-related processes that occur in Earth's crust and upper mantle.
Additional affiliations
July 2010 - March 2013
ETH Zurich
Position
  • PostDoc Position
August 2006 - May 2010
ETH Zurich
Position
  • PhD Student
August 1999 - June 2006
Lakehead University Thunder Bay Campus
Position
  • Bachelor student and master student

Publications

Publications (138)
Conference Paper
Full-text available
The role of inheritance in localizing basement deformation in the foreland has been demonstrated in orogens in different parts of the world. In the external domain of the central Scandinavian Caledonides, questions remain about the amount and the distribution of deformation accommodated by the Baltica basement during Caledonian orogeny. However, to...
Article
Full-text available
Anisotropy of magnetic susceptibility (AMS) and anisotropy of magnetic remanence (AARM and AIRM) are efficient and versatile techniques to indirectly determine rock fabrics. Yet, deciphering the source of a magnetic fabric remains a crucial and challenging step, notably in the presence of ferrimagnetic phases. Here we use X-ray micro-computed tomog...
Article
Full-text available
We report compositional, microstructural and seismic properties from 24 samples collected from the Middle Allochthon (Seve Nappe) of the central Scandinavian Caledonides, and its bounding shear zones. The samples stem both from field outcrops and the continental drilling project COSC-1 and include quartzofeldspathic gneisses, hornblende gneisses, a...
Article
Paleomagnetic studies have been performed on five rapakivi related complexes in Sweden and Finland. Poles of varying quality have been defined and the majority of the ∼1640–1497 Ma poles are clustering on low latitudinal positions. By combining data from ∼1500 Ma intrusions a new high-quality pole (Plat: 13°N; Plon: 190°E; A95: 11°, K: 14) for Balt...
Article
Full-text available
As a petrofabric indicator, anisotropy of magnetic susceptibility (AMS) can potentially be used to infer seismic properties of rocks, and in particular seismic anisotropy. To evaluate the link between AMS and seismic anisotropy we present laboratory measurements of elastic wave velocities and anisotropy of magnetic susceptibility (AMS) for eight sa...
Article
Full-text available
In this study, we report results from three analog models with a similar initial setup and different amounts of bulk shortening, to simulate the development of a thrust imbricate in fold‐and‐thrust belts at different stages. Samples are taken at the back‐ and forethrusts, in the complex forekink zones, and at random distances to thrusts for analysi...
Article
Full-text available
Laboratory-based elastic wave measurements are commonly used to quantify the seismic properties of Earth’s crust and upper mantle. Different types of laboratory apparatuses are available for such measurements, simulating seismic properties at different pressure and temperature. To complement such laboratory measurements, we present a numerical tool...
Preprint
Full-text available
This study presents K-Ar geochronology ages of illite from fault gouge in the crystalline basement in central-western Sweden. Samples of fault gouge were taken from two faults localizing brittle deformation along and within mafic dikes that intrude Paleoproterozoic granites. K-Ar ages from the ten dated fractions span from 823 Ma to 392 Ma. The old...
Article
Full-text available
The Fennoscandian Shield in central Sweden displays a complex structural and compositional architecture that is mainly related to the Proterozoic history of the Baltica paleocontinent. In its western parts, the Precambrian basement is covered by the allochthonous rocks of the Caledonide orogen, and direct information about the underlying crust is r...
Article
Full-text available
The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project aims to characterise the structure and orogenic processes involved in a major collisional mountain belt by multidisciplinary geoscientific research. Located in western central Sweden, the project has drilled two fully cored deep boreholes into the bedrock of...
Conference Paper
Full-text available
Pressure and temperature change simultaneously in the Earth’s crust from surface to depth. Joint pressure and temperature changes influence many different physical properties. There are many studies on samples at elevated pressure, where the influence of open cracks, fractures, voids and pores have been studied. Applying confining pressure has a di...
Article
Full-text available
Magnetic fabric (MF) investigations complemented by geochemical and grain surface analyses of the understudied and controversial marine isotope stage (MIS) 5 b, 4 and 3 loess deposits in the Lower Volga region, Russia show that the material has been transported and deposited by wind and to a large extent experienced post-depositional reworking. Gra...
Conference Paper
Pressure and temperature system changes in the earth crust from surface to a deeper depth. These pressure and temperature changes can influence the physical properties of rocks. There are many studies on samples at elevated pressure, where the influence of open cracks, fractures, voids and pores are introduced. It is expected that applying confinin...
Conference Paper
Full-text available
Calculating anisotropy and better understanding this physical effect is one of the main challenges in geophysics, whether in the size of the field or micro scale. one of the very common methods of calculating seismic anisotropy is to take into account the bulk properties of the material, in a micro-scale, this is based on the average value of Cryst...
Presentation
The benefits of time-varying processes for interpreting geophysical inverse models.
Conference Paper
Full-text available
The benefits of time-varying processes for interpreting geophysical inverse models.
Article
Full-text available
Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred orientation (SPO) of the particle ensemble can then be used as a strain marker that allows reconstruction of the fluid’s veloci...
Conference Paper
The toolbox is developed in the framework of COMSOL multi-physics which is a well established commercial software that is available to a wide range of researchers; it can be used to investigate the compositional and non-compositional effects of minerals on seismic response properties.
Article
Full-text available
Anisotropy of magnetic susceptibility can provide insights into strain distribution in models simulating fold-and-thrust belts. Models with layers of sand and magnetite mixture shortened above adjacent décollements with high and low friction, are used to study the effect of décollement friction on the magnetic fabric. Above high-friction décollemen...
Article
Full-text available
The Tsäkkok Lens of the Scandinavian Caledonides represents the outermost Baltican margin that was subducted in late Cambrian/Early Ordovician time during closure of the Iapetus Ocean. The lens predominantly consists of metasedimentary rocks hosting eclogite bodies that preserve brittle deformation on the μm-to-m scale. Here, we present a multidisc...
Article
Full-text available
The late Quaternary development of the Lower Volga region of Russia is characterized by an alternating influence of marine and continental environments resulting from fluctuations in Caspian Sea level during the last glaciation. However, sediments deposited under continental conditions have received very little research attention compared to the un...
Conference Paper
Full-text available
Seismology offers valuable information about the nature of lithosphere and asthenosphere. Seismic waves are used to investigation the Earth’s crust and upper mantel and to understand their placement and depth. In this respect, outcrop samples’ thin sections provide a wealth of information about the rocks seismic properties. A numerical toolbox is p...
Conference Paper
we investigate the influence of shape (morphological) preferred orientation (SPO), crystallographic preferred orientation (CPO) and the spatial distribution of grains on seismic wave velocity in rocks. This conference has been postponed to 2021, therefore the full and updated version of this publication will be available by next summer.
Article
Full-text available
Magnetic susceptibility in sediments has been thoroughly studied as a paleoenvironmental proxy over the last decades. However, it is unknown to what extent magnetic susceptibility variation is also a diagnostic of different sediment sources. Here we investigate if multiple magnetic susceptibility-based parameters can effectively be used as sediment...
Article
Full-text available
Fault kinematics can provide information on the relationship and assembly of tectonic units in an orogen. Magnetic fabric studies of faults where pseudotachylytes form have recently been used to determine direction and sense of seismic slip in prehistoric earthquakes. Here we apply this methodology to study magnetic fabrics of pseudotachylytes in f...
Conference Paper
Full-text available
Seismic anisotropy is a key property to understand the structure of the crust and mantle. In this contribution, we investigate the influence of shape (morphological) preferred orientation (SPO), crystallographic preferred orientation (CPO) and the spatial distribution of grains on seismic anisotropy in rocks (Bazargan et al., 2018). A numerical too...
Article
Full-text available
Palaeomagnetic records obtained from Arctic Ocean sediments are controversial because they include numerous and anomalous geomagnetic excursions. Age models that do not rely on palaeomagnetic interpretations reveal that the majority of the changes in inclination do not concur with the established global magnetostratigraphy. Seafloor oxidation of (t...
Article
On-line monitoring of drilling mud gas was for the first time applied during continuous wireline coring of the COSC-1 borehole (Jämtland, central Sweden) to analyse formation gases and to identify inflow gas zones. Nearly complete gas records were obtained with 3 m depth resolution from 662 m (installation of the separator for gas extraction) to 17...
Article
The study of rock fabric properties (orientation, planar, linear, anisotropy) is key to unravelling the geological processes that generated them. With advancements in data acquisition and treatment, X-ray micro-computed tomography (µXCT) represents a powerful method to analyse the shape preferred orientation (SPO) of rock-forming elements, includin...
Conference Paper
Full-text available
Innovative Exploration Drilling and Data Acquisition (I-EDDA) was a Network of Infrastructure in the European Institute of Innovation & Technology (EIT) Knowledge and Innovation Community (KIC) "Raw Materials", running from 2016 to 2018. Its purpose was to unite partners from academia and industry to jointly address challenges that are expected to...
Article
Full-text available
Nappe assembly in the Köli Nappe Complex, Jämtland, Sweden, has been associated with in- and out-of-sequence thrusting. Kinematic data from shear zones bounding the Köli Nappe Complex are compatible with this model, but direct evidence from fault zones internally subdividing the nappe complex does not exist. We studied a series of pseudotachylyte e...
Article
Full-text available
Cryptodome and dome collapse is associated with volcanic hazards, such as, explosive eruptions, pyroclastic density currents, and volcanic edifice collapse. The study of the growth and evolution of volcanic domes provides vital information on the link between dome growth and the development of weakness zones that may cause collapse. The Cerro Bayo...
Conference Paper
Calculating anisotropy and a better understanding of this physical effect is one of the main challenges in geophysics, whether in the size of the field or micro scale. one of the very common methods of calculating seismic anisotropy is to take into account the bulk properties of the material, in microscale, this is based on the average value of Cry...
Article
Full-text available
The Yermak Plateau is one of several regions in the Arctic Ocean where paleomagnetism yields controversial results. Despite low sedimentation rates, late Pleistocene paleomagnetic excursions have been reconstructed from many cores in the region, but they are characterized by considerably longer durations when compared to established ones. Self‐reve...
Article
Full-text available
High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Spontaneously, one question emerges-would it be possible to synthesize...
Conference Paper
Full-text available
Among the most important properties of crustal and mantle rocks is seismic anisotropy. Here we present laboratory measurements of directional dependence of elastic waves (velocity anisotropy, shear wave splitting) for eight cubic samples of deformed crustal rocks from central Sweden. The samples originate from a deep drilling investigation in centr...
Article
Anisotropy of magnetic susceptibility data obtained from discrete sub-samples recovered from two Integrated Ocean Drilling Program sites (Expedition 347 sites M0061 and M0062 in the Baltic Sea) by an Advanced Piston Corer are compared to results obtained on sub-samples recovered by replicate 6 m long Kullenberg piston cores. Characteristic natural...
Article
Rock magnetic measurements were carried out on drill core material and hand specimens from the Blötberget apatite – iron oxide deposit in the Bergslagen ore province, south-central Sweden, to characterise their magnetic properties. Measurements included several kinds of magnetic susceptibility and hysteresis parameters. Petrographic and scanning el...
Article
The COSC-1 project drilled the several hundred meters thick basal shear zone of the Lower Seve nappe with mylonites in mica schists, amphibole schists and gneisses. In zones of high magnetic susceptibility from 1910 to 2450 m we studied magnetic and petrographic fabrics, and magnetic mineralogy. Borehole imaging allowed for geographic reorientation...
Conference Paper
Full-text available
Measuring and comparison between shear wave and compressional wave is very important and still an open question between geophysics and geodynamic communities.
Article
Exhumation of the high‐grade metamorphic Seve Nappe Complex and its emplacement between lower‐grade nappes has been related to wedge extrusion in the central Scandinavian Caledonides. To test this hypothesis, the kinematic evolution of the Caledonian nappe pile is studied by systematic structural mapping in central and northern Jämtland, Sweden. St...
Conference Paper
The Ivrea-Verbano Zone (Southern Alps, Italy) is one of the most complete, time-integrated crust-upper mantle archive in the world. It is a unique target for assembling chemical and physical data on the lower crust and testing several hypotheses of formation, evolution, and modification of the continental crust through space and time. In the southe...
Conference Paper
Full-text available
Various seismic data indicate that lower continental crust is highly anisotropic, although the origin of this anisotropy is debated. This debate presents an exciting area of research, but also limits our understanding of the dynamics of lower crust. It is, however, generally agreed upon that the state of the lower crust directly influences the beha...
Conference Paper
Full-text available
Magma often contains elongated crystals, which are embedded in its viscous flow. In solidified magma bodies, one of the principal features observed in the field is the coherent arrangement of crystals or a net polarization of their orientations in that segment. These arrangements are often observed as parallel to the dike or perpendicular to the si...
Conference Paper
Full-text available
Crystallographic preferred orientation (CPO) is one of the principal parameters in causing seismic anisotropy in the lower continental crust and upper mantle. A very common method of calculating seismic anisotropy takes into consideration the bulk properties of the rock, based on the average value of CPO measurements using, for example, Scanning El...
Article
Anisotropy of magnetic susceptibility (AMS) analysis is used as a petrofabric indicator for a set of four identical-setup sandbox models that were shortened by different amounts and simulate contraction in a fold-and-thrust belt. During model shortening, a progressive reorientation of the initial magnetic fabric occurs due to horizontal compaction...
Article
The initial wear, deformation and degradation of cemented carbide in contact with different rock types are studied using a crossed cylinder sliding test. The sliding distance is limited to centimetres at a time, interrupted by successive SEM analysis. This allows for careful studies of the gradually changing microstructure of the cemented carbide d...
Article
Full-text available
Felsic magma commonly pools within shallow mushroom-shaped magmatic intrusions, so-called laccoliths or cryptodomes, which can cause both explosive eruptions and collapse of the volcanic edifice. Deformation during laccolith emplacement is primarily considered to occur in the host rock. However, shallowly emplaced laccoliths (cryptodomes) show exte...
Article
Full-text available
We present calculated seismic velocities and anisotropies of mafic granulites and eclogites from the Cretaceous deep lower crust (∼40–65 km) of Fiordland, New Zealand. Both rock types show a distinct foliation defined by cm-scale compositional banding. Seismic properties are estimated using the Asymptotic Expansion Homogenisation – Finite Element (...
Article
A recent paper in Reviews of Geophysics discussed how the mineral composition and microfabric of the continental crust influences its seismic properties.
Conference Paper
Full-text available
We present a set of AMS measurements on samples from the Siilinjärvi alkaline-carbonatite complex in eastern Finland. The complex has a tabular shape (ca. 16 km long, 1.5 km wide) that strikes north-south and is constrained within a steeply dipping N-S oriented deformation zone. It consists of a mixture of lithologies, including carbonatite, fenite...
Article
Full-text available
Stress-induced borehole deformation analysis in the Collisional Orogeny in the Scandinavian Caledonides deep scientific borehole (COSC-1) establishes in-situ stress orientation in a poorly characterized region in central Sweden. Two acoustic televiewer logging campaigns, with more than one year between campaigns, provide detailed images along the f...
Article
Progress in seismic methodology and ambitious large-scale seismic projects are enabling high-resolution imaging of the continental crust. The ability to constrain interpretations of crustal seismic data is based on laboratory measurements on rock samples and calculations of seismic properties. Seismic velocity calculations and their directional dep...
Conference Paper
Following the recent advent of shale gas and shale oil, especially in the USA, the production of hydrocarbons has increased dramatically. These successes led to evaluation of unconventional shale potential in basins worldwide in the hunt for hydrocarbons previously thought unrecoverable. Several basins were identified in Australia as having hydroca...
Article
Full-text available
Magma transport through the Earth’s crust occurs dominantly via sheet intrusions, such as dykes and cone sheets, and is fundamental to crustal evolution, volcanic eruptions and geochemical element cycling. However, reliable methods to reconstruct flow direction in solidified sheet intrusions have proved elusive. Anisotropy of magnetic susceptibilit...