Studia Geophysica et Geodaetica最新文献

{"title":"Magnetic Fabrics and Provenance Directions of Mid-Late Jurassic Pyroclastic Flows from the Northern Antarctic Peninsula","authors":"Florencia N. Milanese,&nbsp;Laila Iacono,&nbsp;Pablo R. Franceschinis,&nbsp;Florencia Boedo,&nbsp;Miguel Gumina,&nbsp;Carla Puigdomenech Negre,&nbsp;Rodrigo Feo,&nbsp;Joaquín Gil,&nbsp;Jorge Lozano,&nbsp;Julián Agostini,&nbsp;Matías Naselli,&nbsp;Manuel Montes,&nbsp;Augusto E. Rapalini","doi":"10.1007/s11200-026-00015-8","DOIUrl":"10.1007/s11200-026-00015-8","url":null,"abstract":"<div><p>The paleogeographic evolution of the Antarctic Peninsula during the Gondwana breakup remains poorly constrained. Reconstructing the eruptive sources of the voluminous Jurassic Chon Aike Province is crucial for refining or challenging existing tectonic models. This study presents new Anisotropy of Magnetic Susceptibility (AMS) data from Mid-to-Late Jurassic pyroclastic units in the northern Antarctic Peninsula to address these uncertainties. Bulk magnetic susceptibility values between 30–80 µSI, thermomagnetic curves, and hysteresis cycles indicate a normal (non-inverse) AMS fabric. Lack of evidence of tectonic overprint sustains a primary origin for the AMS fabric. Volcanic paleoflow directions were determined using K3 imbrication and, to a lesser extent, K1 magnetic lineations. Our results for the pirolastic Kenney Glacier Formation reveal a significant shift in volcanic sourcing: a source area located to the NW of Mount Flora in the basal units (Kenney 1 and lower Kenney 2 Members). A systematic change in the source area, coming from the ESE in Kenney 2 and 3 and from the SE in Kenney 4 Member. Integrating these results into a ~ 160 Ma paleoreconstruction, we propose a model for the Kenney Glacier Formation that aligns with current tectonic frameworks for the Graham Land Volcanic Group. In this restored geometry, flows originated from the SE (Kenney 1), shifting to the NNW (Kenney 2 and 3), and finally to the NE (Kenney 4). These findings provide evidence of shifting volcanic centers during the V2 episode of Jurassic magmatism in West Gondwana.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic fabrics and paleomagnetism of continental mudrocks: Implications for unravelling the tectonic evolution of the South Pyrenean Zone (NE Spain)","authors":"Pablo Sierra-Campos,&nbsp;Pablo Calvín,&nbsp;Esther Izquierdo-Llavall,&nbsp;Manuel Montes,&nbsp;Aránzazu Luzón,&nbsp;Eva Bellido,&nbsp;Elisabet Beamud,&nbsp;Emilio L. Pueyo,&nbsp;Juan Cruz Larrasoaña","doi":"10.1007/s11200-026-00018-5","DOIUrl":"10.1007/s11200-026-00018-5","url":null,"abstract":"<div><p>The anisotropy of the magnetic susceptibility (AMS) in mudrocks has been widely used to study orogenic belts due to their sensitivity to strain, while paleomagnetism remains the most effective method to quantify vertical axis rotations (VARs) resulting from the accommodation of along-strike variations in shortening. However, AMS can be also eventually used as a passive marker to detect VARs and the integration of both techniques offers a powerful approach to understand the tectonic evolution of fold-and-thrusts-belts. In this work, a combined AMS and paleomagnetic study along a stratigraphic section of continental rocks from the Campodarbe Formation in the Jaca-Pamplona Basin, southern Pyrenees, was carried out. This stratigraphic section (Martes section) records the tectonic evolution of this part of the basin from Priabonian to Rupelian times. The magnetic fabrics show the imprint of early stages of deformation, characterized by dominantly oblate ellipsoids and WNW-ESE horizontal magnetic lineations (axes of maximum magnetic susceptibility k_max), parallel to bedding and the main regional structures. In the lower part of the section, k_max axes trend around 290º, gradually rotating to 270º towards the top. The AMS is interpreted as locked under the imprint of the layer parallel shortening (LPS) associated to the activity of the basement thrusts in the northern Jaca-Pamplona Basin. On the other hand, paleomagnetic data indicate clockwise VARs of 6º to 12º in the lower part of the section, and a counterclockwise rotation of 7º to 14º in the upper part. These differential rotations could result from lateral changes in the Biniés basement thrust or the Jaca thrust system that were active during Oligocene times. Both techniques record a net rotation of ca. 25º between the lower and upper part of the section, which support the interpretation that early-locked AMS behaves as a passive marker and validates its use for detecting and quantifying VARs.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11200-026-00018-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using Scalar Data from the Magnetic Fabric of Shales to Estimate Strain","authors":"Charles Aubourg","doi":"10.1007/s11200-026-00006-9","DOIUrl":"10.1007/s11200-026-00006-9","url":null,"abstract":"<div><p>The utilisation of magnetic fabric constitutes a rapid and non-destructive technique; however, its primary disadvantage is that it is carried by multiple magnetic phases. Consequently, it is imperative to furnish structural geologists with target rocks whose mineralogy is as elementary as possible in order to quantify strain. It is evident that non-metamorphic shales are of interest due to the fact that magnetic susceptibility is primarily exhibited by phyllosilicates, including smectites, illites and chlorites. The use of magnetic fabric facilitates the identification of the contribution of billions of these clay particles. The present study utilises published data to demonstrate the feasibility of employing scalar data for the purpose of monitoring the evolution of vertical compaction during diagenesis, or horizontal compaction during the development of layer-parallel shortening, or strain induced by fault propagation. The examples presented demonstrate that the quantification of strain is possible when cleavage is significantly oblique to the bedding. The extraction of these scalar data is facilitated by the measurement of a minimal quantity of unoriented shale fragments, thereby enabling the execution of large-scale statistical studies.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic Signature of the Camarena de la Sierra Jurassic Magmatism in the SE Iberian Chain (Teruel, Spain)","authors":"Belén Oliva-Urcia,&nbsp;Antonio Cassas-Sainz","doi":"10.1007/s11200-026-00016-7","DOIUrl":"10.1007/s11200-026-00016-7","url":null,"abstract":"<div><p>Magnetic fabrics are commonly studied to understand the magma flow in volcanic and hypovolcanic settings. In this work we present a magnetic fabric study in the Sierra de Javalambre (SE Iberian Chain), a geological unit that includes a swarm of Mesozoic volcanic intrusive and extrusive bodies associated with a hotspot and extensional deformation in Eastern Iberia during the Mesozoic. The sill sampled in this work is constituted by alkaline dolerites (ocean island basalts, OIB composition) and is a part of more than a hundred outcrops emplaced in Upper Triassic (Keuper facies) diapiric units and Jurassic limestones. The presence of Ti-poor titanomagnetite in the studied hypovolcanic rocks is inferred from temperature-dependent magnetic susceptibility curves and also from analyses of the three components isothermal remanent magnetization (IRM), since the decay of the magnetic susceptibility and the soft axis (0.12 mT) of the IRM occurs at 580°C. The magnetic susceptibility shows high values, in average 17554 × 10^–6. The anisotropy of the magnetic susceptibility shows some dispersion of the maximum and intermediate axes on the bedding plane, whereas the minimum axes are clustered almost perpendicular to the bedding plane for the 158 standard analyzed samples. The magnetic lineation (clustering of the maximum axes of the anisotropy of magnetic susceptibility) is bimodal with WNW-ESE and NNE-SSW directions in the in-phase magnetic susceptibility, and can be interpreted as the flow direction of the magma controlled by the NW–SE and N-S extensional fault systems during the basinal (Jurassic) stage.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11200-026-00016-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lineation of the Anisotropy of Magnetic Susceptibility in the Wrench-Dominated Transpression","authors":"Josef Ježek","doi":"10.1007/s11200-026-00011-y","DOIUrl":"10.1007/s11200-026-00011-y","url":null,"abstract":"<div><p>The model of transpression is a standard framework for tectonic studies. It describes homogeneous deformation in a weak zone between two obliquely convergent rigid blocks. Depending on the angle of convergence, pure shear-dominated transpression and wrench-dominated transpression (WDT) can be distinguished in which the lineation (first eigenvector of finite strain ellipsoid) is vertical or switches from initially horizontal to vertical. In practice, lineation is often determined using the AMS method, i.e. based on the preferred orientation of magnetic grains. Under special circumstances, such as transpression, this can lead to differences in lineation defined by the strain ellipsoid and lineation defined by grains. This paper aims to fill the gap in knowledge on this issue. Mathematical modelling based on continuum mechanics quantifies how the switching of lineation in WDT depends on the grain axial ratio. This process is projected into the tensor of magnetic anisotropy and may be further modulated by the presence of subpopulations of magnetic grains or the variability of their shape and magnetic properties. It is shown that the switching of AMS lineation in WDT occurs at lower strain than by the lineation defined by strain ellipsoid.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prevailing-Frequency Approximation of the Coupling Ray Theory within the Weak-Anisotropy Concept I-Theory","authors":"Véronique Farra,&nbsp;Ivan Pšenčík","doi":"10.1007/s11200-026-00001-0","DOIUrl":"10.1007/s11200-026-00001-0","url":null,"abstract":"<div><p>Ray-theory computations of shear (S) waves in inhomogeneous anisotropic media collapse in cases when the two S waves, existing in such media, propagate close to each other. This happens in vicinities of shear-wave singularities or, generally, in weakly anisotropic media. Described problems can be removed by the use of the coupling ray theory. Along a ray, called common S-wave ray, one has to solve repeatedly a system of two frequency-dependent ordinary differential equations. Solutions are sought for frequencies covering the spectrum of the used signal. This complicates computations considerably. In this paper, we use recently proposed approximation, called prevailing-frequency approximation, and apply it to the S-wave coupling ray theory based on the weak-anisotropy approximation. Use of the prevailing-frequency approximation removes the requirement of repeated solution of ordinary differential equations. Instead of it, one has to solve just four ordinary differential equations along a common S-wave ray. It makes the procedure of computing S-wave fields similar to the procedure used for separate S waves or for P waves. In this paper, we derive basic formulae and discuss their properties. We test the derived formulae in specific situations (weak anisotropy, vicinity of a singularity, etc.) in the companion paper. </p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Static Alternating Field Demagnetization of Rocks: Why Three Axes are not Enough","authors":"David Finn,&nbsp;Stuart A. Gilder,&nbsp;Dario Bilardello,&nbsp;Michael R. Wack,&nbsp;Robert S. Coe,&nbsp;Michael Jackson,&nbsp;Wyn Williams,&nbsp;Leon Kaub,&nbsp;Michael J. Branney","doi":"10.1007/s11200-026-00009-6","DOIUrl":"10.1007/s11200-026-00009-6","url":null,"abstract":"<div><p>Paleomagnetism relies4 on stable remanent magnetizations held in rocks to reconstruct the ancient geomagnetic field direction and intensity. However, rocks may carry secondary overprints that obscure or completely destroy the original signal. To study the stability of the magnetic vector(s), laboratories routinely apply static alternating field demagnetization along three orthogonal axes (AFD₃), which is fast, non-destructive, and easy to automate. Here, we present a multiparticle model that shows AFD₃ can deviate the natural remanent magnetization (NRM). Deviations can be avoided when fulfilling two conditions: (i) the NRM was acquired in a weak field where magnetization intensity varies linearly with field strength, and (ii) the sample is magnetically isotropic. The first condition is generally satisfied for rocks holding thermal or detrital remanent magnetizations, but not those affected by an isothermal remanence (e.g., lightning), even though AFD₃ is often used to remove them. In rocks with an anisotropic particle orientation distribution, stepwise AFD₃ progressively removes different coercivity subpopulations as a function of grain orientation so the effective remanence anisotropy of the surviving carriers changes during demagnetization. The anisotropy-driven deflection therefore evolves with AF step, producing curvilinear demagnetization trajectories. Our theoretical results argue for caution when applying AFD₃ to anisotropic samples or those with isothermal overprints. Undesired NRM rotation can be avoided by tumble demagnetization or mitigated by increasing the number of alternating field axis orientations. </p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11200-026-00009-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147441744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-Tensorial Anhysteretic Remanent Anisotropy and the Detection of Composite Fabrics","authors":"David Finn,&nbsp;Michael R. Wack,&nbsp;Stuart A. Gilder,&nbsp;Michael Jackson,&nbsp;Robert S. Coe,&nbsp;Dario Bilardello,&nbsp;Leon Kaub,&nbsp;Wyn Williams,&nbsp;Michael J. Branney","doi":"10.1007/s11200-026-00010-z","DOIUrl":"10.1007/s11200-026-00010-z","url":null,"abstract":"<div><p>The anisotropy of anhysteretic remanent magnetization (AARM) provides a powerful, nondestructive means of assessing magnetic fabrics. It is widely applied to infer strain and emplacement conditions in sedimentary, volcanic, and intrusive rocks. AARM is generally represented by a symmetric second-rank tensor describing its orientation, strength, and shape. AARM, however, departs from a tensorial shape when the number of grains carrying each directionally imparted anhysteretic remanence (ARM) varies with ARM orientation – a condition that arises when the alternating field (AF) over which the ARM is imparted does not fully activate the sample. Experimental data from a highly anisotropic ignimbrite sample, together with multiparticle modeling, show that such partial activation produces non-tensorial AARMs. Although this behavior complicates tensor analysis, non-tensorial AARM can reveal superimposed fabrics, provided that users can apply AF and ARM in a broad range of orientations. This article presents theoretical models that demonstrate non-tensorial behavior and explains how to utilize these properties to discern superimposed fabrics in natural samples.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11200-026-00010-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147429378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropy of Magnetic Susceptibility as a Tool to Understand the Mechanism of Formation of Volcanic Bombs","authors":"Edgardo Cañón-Tapia,&nbsp;Miguel Ángel Carapia-Pérez","doi":"10.1007/s11200-026-00008-7","DOIUrl":"10.1007/s11200-026-00008-7","url":null,"abstract":"<div><p>The mechanism of formation of volcanic bombs is not well-understood at present. Although several alternative models have been proposed, it is difficult to assess them due to the lack of quantitative indicators. Measurement of the anisotropy of magnetic susceptibility (AMS) of different bomb morphologies might provide an useful quantitative reference frame upon which such models can be mutually compared. In this work, we present the results of the measurement of the AMS of six different bomb morphologies. The results show that similar macroscopic morphological types can be achieved by more than one mechanism of deformation, but the internal structure of each bomb retains clues concerning the different mechanisms of deformation that acted upon it before its effective solidification. Bombs of small size may have experienced complex sequences of deformation that are superimposed in different layers of the bomb, but such complexity is not necessarily observed in bombs of larger size, as the latter do not necessarily experienced more complex sequences of deformation events. Furthermore, the breadcrust texture of a bomb may not reflect gas expansion that influenced the entire volume of the bomb, but can be related only with a superficial layer and the flattening of a bomb may be due to rotation effects around an axis, which may be defined by an embedded object. Although the diversity of AMS signals is large, it is considered that this tool provides valuable information that can help us to better understand the mechanism of formation of this type of pyroclastic products.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"70 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147429379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of laterally varying crustal density in gravity interpolation at large data gaps: experiment for the continent Africa","authors":"Hussein A. Abd-Elmotaal,&nbsp;Kurt Seitz,&nbsp;Norbert Kühtreiber,&nbsp;Thomas Grombein,&nbsp;Bernhard Heck,&nbsp;Hansjörg Kutterer","doi":"10.1007/s11200-025-0905-5","DOIUrl":"10.1007/s11200-025-0905-5","url":null,"abstract":"<div><p>One of the great challenges that the IAG Sub-Commission on gravity and geoid in Africa faces is the significantly large gravity data gaps. Simple interpolation of the gravity data does not add new information at the large data gaps. In the present study, new and independent signal information is implemented by using the laterally varying density that influences the gravity signal. Consequently, the global crustal density model UNB TopoDens was introduced as an additional source of information covering the whole area of the continent of Africa. This new independent information, entering the process of generating and updating the African gravity data base, has variable laterally varying density values available as a 30″ × 30″ grid. It has been employed in the framework of the non-ambiguous window remove-restore technique, which produces well smoothed reduced anomalies which minimize the interpolation errors. The lateral crustal density model (CDM) assigns extensive water areas with a density value which is equal to 1000 k gm⁻³, and the oceans with density equal to zero. These values are overruled with valid values in order to correctly compute the impact of topographic masses in the window remove-compute-restore (wRCR) technique. Accordingly, a density model compatible with the computation of the effect of topographic masses within the window remove-restore technique has been developed. A set of Digital Density Models is needed for the computation of the effect of the topographic masses. This has been achieved by the block average operator technique. The impact of the variable density by using a lateral density model compared to the traditional use of a constant density value is discussed in detail. The results proved that the variable crustal density has a significant effect on the interpolated gravity at the large terrestrial gravity data gaps over Africa.</p></div>","PeriodicalId":22001,"journal":{"name":"Studia Geophysica et Geodaetica","volume":"69 2","pages":"177 - 194"},"PeriodicalIF":0.8,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145493440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}