Application of anisotropy of magnetic susceptibility (AMS) fabrics to determine the kinematics of active tectonics: examples from the Betic Cordillera, Spain, and the Northern Apennines, Italy

Abstract. The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to measure fabrics and, in the process, interpret the kinematics of actively deforming orogens. We collected rock fabric data of alluvial fan sediments surrounding the Sierra Nevada massif, Spain, and a broader range of Cenozoic sediments and rocks across the Northern Apennine foreland, Italy, to explore the deformation fabrics that contribute to the ongoing discussions of orogenic kinematics. The Sierra Nevada is a regional massif in the hinterland of the Betic Cordillera. We recovered nearly identical kinematics regardless of specimen magnetic mineralogy, structural position, crustal depth, or time. The principal elongation axes are NE–SW in agreement with mineral lineations, regional GPS geodesy, and seismicity results. The axes trends are consistent with the convergence history of the Africa–Eurasia plate boundary. In Italy, we measured AMS fabrics of specimens collected along a NE–SW corridor spanning the transition from crustal shortening to extension in the Northern Apennines. Samples have AMS fabrics compatible only with shortening in the Apennine wedge and have locked in penetrative contractional fabrics, even for those samples that were translated into the actively extending domain. In both regions, we found that specimens have a low degree of anisotropy and oblate susceptibility ellipsoids that are consistent with tectonic deformation superposed on compaction fabrics. Collectively, these studies demonstrate the novel ways that AMS can be combined with structural, seismic, and GPS geodetic data to resolve orogenic kinematics in space and time.

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Application of anisotropy of magnetic susceptibility (AMS) fabrics to determine the kinematics of active tectonics: Examples from the Betic Cordillera, Spain and the northern Apennines, Italy

10.5194/se-2020-184 ◽

2021 ◽

Author(s):

David J. Anastasio ◽

Frank J. Pazzaglia ◽

Josep M. Parés ◽

Kenneth P. Kodama ◽

Claudio Berti ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Sierra Nevada ◽

Plate Boundary ◽

Active Tectonics ◽

Anisotropy Of Magnetic Susceptibility ◽

Northern Apennines ◽

Alluvial Fan ◽

Betic Cordillera ◽

Tectonic Deformation ◽

Gps Geodesy

Abstract. The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to measure fabrics and in the process, interpret the kinematics of actively deforming orogens. We collected rock fabric data of alluvial fan sediments surrounding the Sierra Nevada massif, Spain, and a broader range of Cenozoic sediments and rocks across the northern Apennine foreland, Italy, to explore the deformation fabrics that contribute to the ongoing discussions of orogenic kinematics. Sierra Nevada is a regional massif in the hinterland of the Betic Cordillera. We recovered nearly identical kinematics regardless of specimen magnetic minerology, structural position, crustal depth, or time. The principal elongation axes are NE-SW in agreement with mineral lineations, regional GPS geodesy, and seismicity results. The axes trends are consistent with the convergence history of the Africa-Eurasia plate boundary. In Italy, we measured AMS fabrics of specimens collected along a NE-SW corridor spanning the transition from crustal shortening to extension in the northern Apennines. Samples have AMS fabrics compatible only with shortening in the Apennine wedge and have locked in penetrative contractional fabrics, even for those samples that were translated into the actively extending domain. In both regions we found that specimens have a low degree of anisotropy and oblate susceptibility ellipsoids that are consistent with tectonic deformation superposed on compaction fabrics. Collectively, these studies demonstrate the novel ways that AMS can be combined with structural, seismic, and GPS geodetic data to resolve orogenic kinematics in space and time.

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The emplacement mode of Upper Cretaceous plutons from the southwestern part of the Sredna Gora Zone (Bulgaria): structural and AMS study

Geologica Carpathica ◽

10.2478/v10096-009-0001-8 ◽

2009 ◽

Vol 60 (1) ◽

pp. 15-33 ◽

Cited By ~ 16

Author(s):

Neven Georgiev ◽

Bernard Henry ◽

Neli Jordanova ◽

Nikolaus Froitzheim ◽

Diana Jordanova ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Shear Zone ◽

Upper Cretaceous ◽

Plate Boundary ◽

Shear Zones ◽

Anisotropy Of Magnetic Susceptibility ◽

Southwestern Part ◽

Structural Investigations ◽

Plate Convergence ◽

Microgranular Enclaves

The emplacement mode of Upper Cretaceous plutons from the southwestern part of the Sredna Gora Zone (Bulgaria): structural and AMS study Several plutons located in the southwestern part of the Sredna Gora Zone — Bulgaria are examples of the Apuseni-Banat-Timok-Sredna Gora type of granites emplaced during Late Cretaceous (86-75 Ma) times. The studied intrusive bodies are spatially related to and deformed by the dextral Iskar-Yavoritsa shear zone. The deformation along the shear zone ceased at the time of emplacement of the undeformed Upper Cretaceous Gutsal pluton, which has intruded the Iskar-Yavoritsa mylonites. A clear transition from magmatic foliation to high-, moderate- and low-temperature superimposed foliation and lineation in the vicinity of the Iskar-Yavoritsa and related shear zones gives evidence for simultaneous tectonics and plutonism. Away from the shear zones, the granitoids appear macroscopically isotropic and were investigated using measurements of anisotropy of magnetic susceptibility at 113 stations. The studied samples show magnetic lineation and foliation, in agreement with the magmatic structures observed at a few sites. Typical features of the internal structure of the plutons are several sheet-like mafic bodies accompanied by swarms of mafic microgranular enclaves. Field observations indicate spatial relationships between mafic bodies and shear zones as well as mingling processes in the magma chamber which suggest simultaneous shearing and magma emplacement. Structural investigations as well as anisotropy of magnetic susceptibility (AMS) data attest to the controlling role of the NWSE trending Iskar-Yavoritsa shear zone and to the syntectonic emplacement of the plutons with deformation in both igneous rocks and their hosts. The tectonic situation may be explained by partitioning of oblique plate convergence into plate-boundary-normal thrusting in the Rhodopes and plate-boundary-parallel transcurrent shearing in the hinterland (Sredna Gora).

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Deformation understanding in the Upper Paleozoic of Ventana Ranges at Southwest Gondwana Boundary

Scientific Reports ◽

10.1038/s41598-021-99087-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Guadalupe Arzadún ◽

Renata Nela Tomezzoli ◽

Natalia Fortunatti ◽

Nora Noemi Cesaretti ◽

María Belén Febbo ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Buenos Aires ◽

Anisotropy Of Magnetic Susceptibility ◽

Tectonic Deformation ◽

Thin Sections ◽

Polar Wander ◽

Apparent Polar Wander Path ◽

Upper Paleozoic ◽

San Rafael

AbstractAt the east of the Ventana Ranges, Buenos Aires, Argentina, outcrops the Carboniferous-Permian Pillahuincó Group (Sauce Grande, Piedra Azul, Bonete and Tunas Formation). We carried out an Anisotropy of Magnetic Susceptibility (AMS) study on Sauce Grande, Piedra Azul and Bonete Formation that displays ellipsoids with constant Kmax axes trending NW–SE, parallel to the fold axes. The Kmin axes are orientated in the NE–SW quadrants, oscillating from horizontal (base of the sequence-western) to vertical (top of the sequence-eastern) positions, showing a change from tectonic to almost sedimentary fabric. This is in concordance with the type and direction of foliation measured in petrographic thin sections which is continuous and penetrative to the base and spaced and less developed to the top. We integrated this study with previous Tunas Formation results (Permian). Similar changes in the AMS pattern (tectonic to sedimentary fabric), as well as other characteristics such as the paleo-environmental and sharp curvature in the apparent polar wander path of Gondwana, marks a new threshold in the evolution of the basin. Those changes along the Pillahuincó deposition indicate two different spasm in the tectonic deformation that according to the ages of the rocks are 300–290 Ma (Sauce Grande to Bonete Formation deposition) and 290–276 Ma (Tunas Formation deposition). This Carboniferous-Permian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpreted as the result of rearrangements of the microplates that collided previously with Gondwana, and latitudinal movements of Gondwana toward north and Laurentia toward south to reach the Triassic Pangea.

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Active tectonics in the Sierra Nevada (Betic Cordillera, SE Spain): Insights from geomorphic indexes and drainage pattern analysis

Geomorphology ◽

10.1016/j.geomorph.2010.02.020 ◽

2010 ◽

Vol 119 (1-2) ◽

pp. 74-87 ◽

Cited By ~ 164

Author(s):

José Vicente Pérez-Peña ◽

Antonio Azor ◽

José Miguel Azañón ◽

Edward A. Keller

Keyword(s):

Sierra Nevada ◽

Pattern Analysis ◽

Active Tectonics ◽

Betic Cordillera ◽

Drainage Pattern ◽

Se Spain

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The Petrology of Gabbroids of the Anagram Islands (Wilhelm Archipelago, West Antarctica)

Mineralogical Journal ◽

10.15407/mineraljournal.42.04.069 ◽

2020 ◽

Vol 42 (4) ◽

pp. 69-83

Author(s):

O.V. MYTROKHYN ◽

V.G. BAKHMUTOV ◽

A.G. ALEKSIEIENKO ◽

T.V. MYTROKHINA

Keyword(s):

Magnetic Susceptibility ◽

Geological Structure ◽

Anisotropy Of Magnetic Susceptibility ◽

Tectonic Deformation ◽

West Antarctica ◽

Bottom Part ◽

Magnetic Susceptibility Data ◽

Susceptibility Data ◽

Mode Of Occurrence ◽

Field Works

The Anagram Islands are located near the Graham Coast of West Antarctica not far from the Ukrainian Antarctic Station "Akademik Vernadsky". Gabbroids that are probably Cretaceous in age predominate in the geological structure of the Anagram Islands. New data on the mode of occurrence of the Anagram gabbroids and their layering were obtained during the seasonal field works of the Ukrainian Antarctic Expeditions in 2017, 2019-2020 years. Samples of the gabbroids were examined by optical microscopy, electron microscopy and microprobe analysis as well as by measuring of anisotropy of magnetic susceptibility of rocks. The goal of the research was to clarify the geological position and petrographic features of the Anagram gabbroids, to determine the typomorphic features of rock-forming minerals, and to clarify the origin of the layering in gabbroids. It was determined that the bottom part of a large layered gabbroid intrusion is fragmentarily exposed on the Anagram Islands. The continuation of the intrusion is expected in the northeastern and southeastern directions. It was established that primary magmatic textures and mineral composition are preserved in the gabbroids despite the development of metamorphic amphibolization. The gabbroids show typical cumulative textures of magmatic origin. The main cumulative phases are plagioclase (An70-95), clinopyroxene (Wo41-49En34-47), orthopyroxene (Wo2-4En49-71), olivine (Fo67-69), Ti-magnetite and ilmenite. It is proved that the fine rhythmic-gradational layering in the gabbroids was formed by gravitational precipitation of the cumulative minerals on the bottom of the magma chamber and their further sorting by specific gravity due to convection currents. Cryptic layering is firstly discovered in the Anagram gabbroids and is explained by the processes of crystallization differentiation. The latter caused the accumulation of the most calcium plagioclases and the most magnesian mafic minerals in the layered gabbroids forming the bottom part of the intrusion. The present subvertical position of layering is explained by tectonic deformation that resulted in the tilting of the investigated section of the Anagram gabbroid intrusion. This confirmed by the studying of magnetic texture of the gabbroids (by the anisotropy of magnetic susceptibility data).

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