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Abstract The study of sedimentary magnetism in the intermontane Tarom Basin (northern Iran) offers insights into local paleoenvironmental conditions during global middle‐late Miocene climate changes and the topographic growth triggered by the Arabia‐Eurasia continental collision. Rock magnetic results reveal that the ∼16.2 to ∼10–9 Ma coarse‐grained deposits at the basin's southern margin present a homogenous magnetic mineral assemblage, reflecting sediment provenance. Conversely, the ∼13.2 to ∼7.6 Ma, fine‐grained deposits in the basin's depocenter include alternating playa‐lake and lacustrine deposits, recording dry, evaporative conditions, leading to hematite formation in a low‐temperature oxidizing environment, and wetter conditions that preserve the original detrital signal, respectively. Time series analyses show cyclicity in different period bands for magnetic susceptibility, but precession and obliquity cycles can hardly be resolved in the record. Comparison with deep‐sea oxygen isotope data suggests that from ∼13.2 to ∼10.8 Ma environmental conditions likely mirrored global climatic forcing, with lacustrine and playa‐lake deposits associated with increased and decreased global temperature, respectively. At ∼10.8 Ma, the basin likely recorded the Tortonian Thermal Maximum with the establishment of a lacustrine system. From ∼10.4 Ma, the magnetic susceptibility signal departed from the global climate record, possibly due to basin margin (western Alborz and Tarom mountains) and regional (Anatolian‐Iranian plateau) topographic growth, accompanied by increased precipitation seasonality, focused rainfall and augmented erosion rates. Finally, we suggest that before ∼10.8 Ma, the Hadley cells expanded northward, leading to a trade‐dominated system with moist air masses sourced from the Caspian, while from ∼10.8 Ma, westerlies dominance progressively prevailed. 

SUMMARY A detailed rock magnetic study was conducted on ash samples collected from different products erupted during explosive activity of Mount Etna, Italy, in order to test the use of magnetic properties as discriminating factors among them, and their explosive character in particular. Samples include tephra emplaced during the last 18 ka: the benmoreitic Plinian eruptions of the Pleistocene Ellittico activity from marine core ET97-70 (Ionian Sea) and the basaltic Holocene FG eruption (122 BC), the Strombolian/Phreatomagmatic/sub-Plinian eruptions (namely, the Holocene TV, FS, FL, ETP products and the 1990, 1998 eruptions) collected from the slope of the volcano, and the Recent explosive activity (lava fountains referred to as ‘Ash Rich Jets and Plumes’, or ARJP) that occurred in the 2001–2002 period, related to flank eruptions. Mössbauer spectrometry informs that a single magnetic mineral dominates the three groups, which are characterized by variable magnetic grain sizes and composition. Detailed rock-magnetic investigations, ranging from low temperature to high temperature remanence and susceptibility experiments, indicate that the more explosive products of the Plinian eruptions and ARJP activity tephra, are characterized by oxidized Ti-rich titanomagnetites, with dominant Curie Temperatures between 230 and 330 °C. The FG and ARJP tephra are also characterized by contrasting, yet overall higher, coercivity distributions and higher magnetizations and susceptibilities, including below room temperature. In contrast, most of the Strombolian/sub-Plinian eruptions have a magnetic signature dominated by less coercive magnetite and/or Ti-poor titanomagnetite. Magnetic differences observed between the Late Pleistocene and Holocene FG Plinian eruptions can be attributed to the different composition of the former eruptions, which were fed by more evolved magmas, whereas geochemical variations characterizing the products erupted in the last few decades can be responsible for the differences between the Holocene and recent Strombolian/sub-Plinian products. Importantly, detailed magnetic investigation of sideromelane and tachylite clasts, the two end members of the juvenile fraction extracted from the ash of the most explosive products, determines that the tachylite fraction is responsible for the magnetic signature of the Plinian FG and ARJP tephra, and is attributed to the intense fragmentation that characterizes these activities, likely resulting from undercooling processes. Moreover, the abundant superparamagnetic grains associated with these eruptive styles are believed to represent the nanolite fraction responsible for the increasing viscosity of these magmas, and to be responsible for their explosive character. The distinctive magnetic properties that characterize the tachylite-bearing tephra, representative of the fragmentation process that distinguishes the most explosive activities, provides a useful magnetic tool that can complement traditional volcanological investigations. 

Abstract High‐temperature Raman spectroscopy offers a cost‐effective alternative to extensive infrastructure and sensitive instrumentation for investigating nanolite crystallization in undercooled volcanic melts, a key area of interest in volcanology. This study examined nanolite formation in anhydrous andesite melts in situ at high temperatures, identifying distinct Raman peaks at 310 and 670 cm⁻¹appearing above the glass transition temperature. The initial amorphous glass remained stable up to 655°C, beyond which Fe‐Ti‐oxide nanolites progressively formed at higher temperatures, as also confirmed by complementary XRD analysis. The evolution of the 310 cm⁻¹peak depends only on the magnitude of nanolite crystallization, while the intensity of the 670 cm⁻¹peak is temperature‐dependent and challenging to observe above 500°C. Complementary low‐temperature rock‐magnetic analyses confirmed Fe‐Ti‐oxide nanocrystallization with nanolites around 20 nm in diameter. The study tested lasers of different wavelengths (from 355 to 514 nm) and found the green laser to be the most effective for collecting spectra at both room and high temperature. However, above 720°C, black body radiation significantly hinders Raman observation with the green laser when using a non‐confocal setup and analyzing poorly transparent samples. If higher temperature measurements are desired, switching to a confocal setup and using lower wavelength lasers should be considered. This research offers a protocol for studying nanolite formation and melt dynamics at high temperatures, providing a foundation for future studies of volcanic processes. 

Abstract Sedimentary rocks of the Itararé Group, deposited during the Late Paleozoic Ice Age in the Paraná Basin of South America, were collected throughout the state of São Paulo, Brazil, for an anisotropy of magnetic susceptibility (AMS) and rock‐magnetic study. A recent paleomagnetic study conducted on the same samples had determined that these rocks were largely remagnetized during the Cretaceous; however, rock‐magnetic experiments demonstrate that the AMS is dominantly carried by paramagnetic minerals and therefore is unaffected by the secondary magnetic overprints. AMS data are analyzed in terms of their shape and orientation, and according to the relationship between theq‐value (magnetic lineation/foliation) and the imbrication angle (β) of the minimum susceptibility axes with respect to bedding (q–βdiagram). Using multiple lines of evidence, we demonstrate that AMS records primary sedimentary fabrics that reflect the depositional environments and paleocurrent conditions in which these rocks were deposited. The magnetic fabrics consistently record a SE‐NW paleocurrent orientation, with dominant direction of transport to the NW throughout the entire state of São Paulo, in agreement with ice flow and sediment transport directions reported from limited numbers of sites possessing sedimentary structures and ice‐kinematic indicators. 

Abstract Basal ice of glaciers and ice sheets frequently contains a well-developed stratification of distinct, semi-continuous, alternating layers of debris-poor and debris-rich ice. Here, the nature and distribution of shear within stratified basal ice are assessed through the anisotropy of magnetic susceptibility (AMS) of samples collected from Matanuska Glacier, Alaska. Generally, the AMS reveals consistent moderate-to-strong fabrics reflecting simple shear in the direction of ice flow; however, AMS is also dependent upon debris content and morphology. While sample anisotropy is statistically similar throughout the sampled section, debris-rich basal ice composed of semi-continuous mm-scale layers (the stratified facies ) possesses well-defined triaxial to oblate fabrics reflecting shear in the direction of ice flow, whereas debris-poor ice containing mm-scale star-shaped silt aggregates (the suspended facies ) possesses nearly isotropic fabrics. Thus, deformation within the stratified basal ice appears concentrated in debris-rich layers, likely the result of decreased crystal size and greater availability of unfrozen water associated with high debris content. These results suggest that variations in debris-content over small spatial scales influence ice rheology and deformation in the basal zone.