The Middle Eocene Senj Mo–Cu deposit (1.3 Mt at 1.5 wt % Cu and 0.2 wt % Mo) is located in the central Alborz magmatic belt, northern Iran. Mineralization is characterized by multistage veins, which are hosted in volcanic and volcano-sedimentary strata of the Karaj Formation (c. 41–45 Ma), genetically associated with the Senj Mafic Sill (c. 40 Ma). Four generations of veins are documented based on mineral assemblages and cross-cutting relationships, sequentially: quartz–biotite–chalcopyrite (QBC veins), quartz–molybdenum (QM veins), quartz–pyrite (QP veins) and late calcite (LC veins). Three types of fluid inclusions (FIs) are present in multistage veins: liquid-rich two-phase (L-type), vapour-rich two-phase (V-type) and solid-bearing multi-phase (S-type) inclusions. FIs in the QBC and QM veins are predominantly V-type and S-type, together with minor L-type, whereas the QP and LC vein minerals only contain L-type fluid inclusions. The homogenization temperatures of FIs from QBC to LC veins vary from 320 to 425 °C, 308 to 390 °C, 214 to 288 °C and 145 to 243 °C, and their salinities range from 5.3 to 49.0, 6.2 to 39.7, 5.7 to 13.0, and 2.1 to 7.2 wt % NaCl equiv., respectively. The H–O–C isotope compositions favour a dominantly magmatic origin for the hydrothermal fluids, which were gradually diluted by meteoric waters. The S–Pb isotope data of sulphide minerals indicate that the sulphur and metals were sourced from a deep-seated magmatic reservoir. The Senj Mafic Sill and associated Mo–Cu mineralization was developed in a back-arc extension regime, which faults and crustal fracture systems served as conduits for hydrothermal fluid circulation and Mo-rich veining.

Late Paleozoic strata in the southeastern Ordos Basin comprise targeted reservoirs for tight gas exploration. As a typical intracratonic basin, the Ordos Basin is characterized by low-accommodation space and a complex sediment infilling process, which attracts much attention. During the early Permian, the southeast area was fed by sediments from multiple sediment sources, which makes it difficult to identify the pinch-out of the sand bodies and reconstruct the sediment routing system. In this study, we reconstruct the paleo-topography of the late Paleozoic setting using high-resolution 2D and 3D seismic data. Thus, we identify two types of topography: the eastern block is presented as a semiclosed depression, and the western block is observed as a flat platform. Based on detrital zircon U–Pb data and heavy mineral assemblages, we reconstruct the provenance area and show that early Permian sediments originate from the northern margin of the Ordos Basin and from the northern Qinling orogenic belt in the south. By integrating the trace element contents, carbon and oxygen isotope data and sedimentary structure from core samples, we can observe the paleoenvironment and the corresponding facies associations in these blocks. The eastern block was infilled by a prograding delta; the western block was infilled by a tide-dominated delta or a wavy-dominated delta. By using stratigraphic forward modelling, we find that most sediments in the semiclosed setting are progradational and intensely interacted. In contrast, the sediments in the western block present an open setting, infilled and gently interacted. The fine-grained deposits were not easily preserved due to tidal or wave reworking processes in the shallow-water marine setting, and they were transported into deep-water areas. Furthermore, to explore the dominant factors in a pattern of fluvial–deltaic sand bodies formed in the low-accommodation basin, we rebuild the sediment routing system parameters and plot them on a bubble chart. According to the fitness between the depositional volume and the above parameters, we determine the key factors in the routing systems that formed. The results show that the sediment supply has a high relevance to the depositional volume in a semiclosed setting, such as the eastern block, while the terrain height may drive sedimentation in an open marine setting, such as the western block. We demonstrate that two different infill patterns and different sand-body stacking patterns with multiple sediment sources in a low-accommodation basin may serve as a model for similar settings.

The presence of recently intruded granites at Earth’s surface suggests that their exhumation may have occurred rapidly. The Neogene granites of the Tuscan Magmatic Province (Italy) were emplaced during a period of extensional tectonics and are ideal for determining and quantifying the exhumation process. The peraluminous monzogranite of Giglio Island in the northern Tyrrhenian Sea is characterized by the presence of roof pendants, xenoliths and miarolitic cavities. The petrologic study of metamorphic xenoliths and new zircon U–Pb ages show that the granite was emplaced at 6.4–10 km depth at 5.7 ± 0.4 Ma. Exhumation, constrained by apatite (U–Th)/He ages, was essentially complete in 0.9 Myr at a minimum rate of 6 mm/year. This requires rapid tectonic unroofing, isostatic rebound and thermal softening activity, weakening the upper crust and favouring exhumation at a previously undocumented rate.

Trilobite moulting behaviour has been extensively investigated. However, exuviae in eodiscid trilobites are poorly known. Here, we report two eodiscid trilobite specimens, Tsunyidiscus niutitangensis and Tsunyidiscus sp., showing Somersault configuration from the Niutitang Formation and Mingxinsi Formation of South China, respectively (Cambrian Series 2, Stage 3). The arrangements of the exoskeletons indicate that the two specimens are the slightly disturbed and undisturbed exuviae. The impression of the lower cephalic unit (LCU) displays the rostral plate in Tsunyidiscus niutitangensis. The exuviae showing the LCU inverted anteriorly under the trunk. The opening of the facial and rostral sutures would have allowed the emergence of the post-ecdysial trilobite with the partial enrolment of exoskeleton. Moreover, our discovery indicates a Somersault configuration which employed the facial and rostral sutures to create an anterior exuvial gape that also exists in eodiscid trilobites besides redlichiid trilobites, corynexochid trilobites and ptychopariid trilobites during the Cambrian.

During late Carboniferous time, the residual ocean basin gradually closed in West Junggar and only a small amount of seawater remained in the Hala’alat Mountain area, where discussions of provenance and tectonics are limited. In this study, LA-ICP-MS U–Pb dating and heavy mineral identification are conducted on the upper Carboniferous tuffaceous sandstones from the Hala’alat and Aladeyikesai formations in the Hala’alat Mountain area. The results reveal the low maturity of the clastic sediments, indicating proximal deposition. The Hala’alat Formation detrital zircons present a single peak (c. 330 Ma). Speculatively, the primary provenance is the Boshchekul–Chingiz Arc, and the secondary sources are the Darbut Tectono-Magmatic Belt and island arcs in the basin. The main peak and provenance of the Aladeyikesai Formation are similar to those of the Hala’alat Formation. Moreover, several age groups, namely, 370–344 Ma, 427–404 Ma and 478–476 Ma, potentially correspond to provenances of the Darbut Tectono-Magmatic Belt, the Boshchekul–Chingiz Arc and the Kujibai–Hongguleleng Ophiolitic Mélange Belt. In addition, the maximum depositional ages of the Hala’alat and Aladeyikesai formations calculated are 314.6 ± 1.54 Ma and 330.8 ± 0.61 Ma, respectively. Comprehensive analysis shows a relatively singular provenance of the Hala’alat Formation. While the provenance of the Aladeyikesai Formation shows inheritance, the provenance area extends northwards to the Kujibai–Hongguleleng Ophiolitic Mélange Belt. Furthermore, the closure of the Junggar Ocean during Carboniferous time caused the potential source region of the Hala’alat Mountain area to migrate northeastwards from Barleik Mountain to Xiemisitai Mountain. This study provides a basis for the analysis of regional geological evolution.

Conodonts are an important biostratigraphic tool for many Phanerozoic stages. Along with graptolites, they define all global Ordovician Stage boundaries. Within the Upper Ordovician interval, a known species of Amorphognathus tvaerensis (Bergström) is present in both Sandbian and Katian stratotype sections. Study of changes in the succession of A. tvaerensis revealed that elements in the upper part of its range differ morphologically quite distinctly from those in its lower part. Here, they are described as a new conodont species, A. viirae sp. nov. This new species is recognized in several Estonian and Swedish sections, with apparent occurrence also in Mójcza Quarry, Holy Cross Mountains, Poland and Black Knob Ridge, Oklahoma, USA. Detailed analysis of early Amorphognathus elements from Estonian and Swedish sections revealed the absence of A. inaequalis (Rhodes) in both regions, although a conodont subzone based on this species was identified earlier by some authors. Both the absence of A. inaequalis (Rhodes) and recognition of the new species A. viirae sp. nov. resulted in the revision of the conodont zonation, and a new version of it is proposed for the Sandbian Stage in the Atlantic Realm. The new zonation includes (from below) Pygodus anserinus, Baltoniodus variabilis, A. tvaerensis, B. gerdae, A. viirae and B. alobatus Conodont zones.

In the Late Neoarchaean, the lithosphere of the North China Craton (NCC) experienced a strong extensional event, which is of great significance for understanding the evolution of the continental crust in the Precambrian. In this study, a suite of mafic dykes from Shandong province in the northeastern NCC were investigated to determine the nature, timing and source of rift-related magma activities using zircon U–Pb data, whole-rock geochemistry and Nd–Hf isotopes. Zircon U–Pb dating of four dolerites by laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) yielded weighted mean 207Pb/206Pb ages in the range 2509 ± 6.1 to 2537 ± 6.2 Ma (2σ, 95 % confidence interval). The mafic dykes are classified as alkaline rocks based on their K2O + Na2O contents (6.78–7.21 wt %) and belong to the shoshonitic series according to their K2O contents (3.23–3.36 wt %). The dolerites show low concentrations of light rare earth elements ((La/Yb)N between 7.17 and 8.55), positive Eu anomalies (Eu/Eu* between 1.12 and 1.27), positive Ba, K, Pb, Sr, Eu, Dy and Lu anomalies, and depleted U, Nb, Pr, Ta, P, Nd and Ti anomalies. The dykes are characterized by low initial (87Sr/86Sr)i (∼0.6969), positive εNd(t) values (0.2–0.8) and εHf(t) values (0.5–8.6) and relatively old mean Nd and Hf model age (2.73 Ga). Collectively, the data suggest that the mafic dykes were derived from the partial melting (10–20 %) of an isotope-depleted garnet–lherzolite mantle source that was hybridized through interaction with subducted lower crustal material. The parental magmas of these dykes underwent a certain number of crustal contaminations during magma ascent. The mafic magmatism represented in the form of the dyke swarms is considered to be a response to widespread lithospheric extension which affected the NCC at c. 2.5 Ga during the Neoarchaean.

The mid-Tournaisian black radiolarian cherts of the Lydiennes Formation are exposed in deep-shelf successions of the Puech de la Suque and Col des Tribes sections of the Mont Peyroux Nappe area in the Montagne Noire, southern France. This interval represents the mid-Tournaisian anoxic event that is also termed the Lower Alum Shale Event. This event is associated with a global marine transgression that was characterized by increased productivity and drastic facies changes from pelagic carbonate sedimentation to the widespread deposition of black organic-rich siliceous shales and radiolarites in many parts of the world. In the present study, high-resolution inorganic geochemistry and framboidal pyrite analyses were employed to decipher changes in depositional conditions during the mid-Tournaisian anoxic event in the Montagne Noire. The results show that the total organic carbon contents of sediments associated with the Lower Alum Shale Event vary from 0.09 to 1.9 wt %. These low to moderate total organic carbon contents, high U/Th, low Corg/P and intermediate V/Cr ratios, enrichment in redox-sensitive trace elements, such as U, Mo and V, as well as varying sizes of pyrite framboids, indicate periodic dysoxic to anoxic bottom-water conditions during deposition of the studied sediments. Anomalous Hg spikes (>500 ppb) are also reported in the mid-Tournaisian deep-water marine succession of the Montagne Noire in the present study, which confirm a possible influence of increased regional volcanic activity during this environmental turnover.

Lamprophyre dikes and quartz veins in the Sizhuang gold deposit are used to date and unravel the Early Cretaceous stress regime in the Jiaodong Peninsula, North China Craton. The lamprophyre dikes are grouped into two major sets, trending NNW–SSE and NNE–SSW, respectively, and a subsidiary one, trending WNW–ESE, whereas the quartz veins trend mainly NNE–SSW. The age of lamprophyre dikes’ intrusion was robustly calculated at c. 119 Ma by phlogopite 40Ar–39Ar dating. The fuzzy clustering technique defined four stress states, which were grouped into three stress regimes in Sizhuang. Furthermore, these stress regimes were interrelated with two regional far-field stress regimes, ST1 and ST2, defined by the available published fault-slip data near Sizhuang by applying the separation and stress inversion TR method (TRM). The palaeostress reconstruction indicates that extension and strike-slip tectonics (i.e. transtension) affect the emplacement of the lamprophyre dikes and quartz veins. More precisely, the dike emplacement occurred under unstable stress conditions related to the shift from E–W pure extension–transtension to WNW–ESE transtension, whereas the quartz veins formed under relatively stable WNW–ESE transtension with the variant and increasing fluid pressure ( ${P_{\rm{f}}})$ giving rise to the strike-slip against dip-slip kinematics along the faults. The change from the ST1 to ST2 stress regimes reflects the significant clockwise rotation in the palaeo-Pacific plate subduction direction and defines the switching time at c. 119 Ma as precisely obtained by the lamprophyre dating.

The congruence between rock quantity and biodiversity through the Phanerozoic has long been acknowledged. Rock record bias and common cause are the most discussed hypotheses: the former emphasizes that the changes in diversity through time fully reflect rock availability; the latter posits that the correlation between rock and fossil records is driven by a common cause, such as sea-level changes. Here, we use the Geobiodiversity Database (GBDB), a large compilation of the rock and fossil records, to test the rock bias hypothesis. In contrast to other databases on fossil occurrences, the section-based GBDB also records unfossiliferous units. Our multiple regression analysis shows that 85% of the variation in sampled diversity can be attributed to the rock record, meaning that major peaks and drops in observed diversity are mainly due to the rock record. Our results support a strong covariation between the number of unfossiliferous units and sampled diversity, indicating a genuine rock bias that arose from sampling effort that is independent of fossil content. This provides a compelling argument that the rock record bias is more prominent than common cause in explaining large-scale variations in sampled diversity. Our study suggests that (1) no single proxy can fully represent rock record bias in predicting biodiversity, (2) rock bias strongly governs sampled diversity in both marine and terrestrial communities, and (3) unfossiliferous strata contain critical information in predicting diversity of marine and terrestrial animals.

The Diwani hills are located SE of Balaram–Abu Road in the Banaskantha district of north Gujarat. The crystalline rocks of the Diwani hill area are a diverse assemblage of Precambrian metamorphic and igneous rocks. These rocks are petrologically more complex and date back to the Aravallis or earlier. The mineralogical assemblages such as grt–sp–opx–qz of these rocks indicate their origin in anhydrous or dry conditions, implying metamorphism under pyroxene granulite facies. These granulitic rocks were subjected to Delhi orogenic deformation and were later intruded by the Erinpura granite. Textural and microstructural relationships, mineral chemistry, P–T–X pseudosection modelling and the oxidation state of pelitic granulites from the Diwani hill area of north Gujarat are all part of the current approach. The winTWQ program and pseudosection modelling in the NCKFMASHTO model system utilizing Perple_X software were used to restrict the P–T evolution of these pelitic granulites. The unification of these estimates shows that the pelitic granulites reached their pressure and temperature maxima at 8.6 kbar and 770 °C, respectively. The oxygen fugacity (log fO2) versus temperature computations at 6.2 kbar revealed log fO2–T values of −13.0 and 765 °C, respectively. The electron microprobe dating of monazite grains separated from the granulites of the Diwani hills yields ages ranging from 769 Ma to 855 Ma. The electron microprobe dating presented here from the Diwani hills provides evidence for a Neoproterozoic (Tonian) metamorphic event in the Aravalli–Delhi Mobile Belt.

The Nama Group, Namibia (≥550.5 to <538 million years ago, Ma), preserves one of the most diverse metazoan fossil records of the terminal Ediacaran Period. We report numerous features that may be biological in origin from the shallow marine, siliciclastic, lowermost Mara Member (older than ca. 550.5 Ma) from the Tsaus Mountains. These include forms that potentially represent body fossils, Beltanelliformis and an indeterminate juvenile uniterminal rangeomorph or arboreomorph frond, plug trace fossils, Bergaueria, as well as sedimentary surface textures, which are possibly microbially induced. These are the oldest documented macrofossils in the Nama Group. They represent taxa that persist from the Avalon or White Sea assemblages prior to the later appearance of new biota, including calcified metazoans, calcified and soft-bodied tubular taxa including all cloudinids, as well as more complex trace fossils.

Using a new age model that allows more accurate stratigraphic placement of major Ediacaran macrofossil morphogroups and taxa, we propose a re-definition of the Nama Assemblage following the practice for Phanerozoic evolutionary faunas to include only new morphogroups of soft-bodied tubular, calcified taxa and complex trace fossils, defined by first appearance of Cloudina, which postdates deposition of the Kanies and lower Mara members and first appears ca. 550 Ma and persists until at least 539 Ma.

Finally, the Tsaus Mountain environment is pristine, unspoilt by geologists and naturalists. Following World Heritage Convention, we suggest a pledge of non-destructive excavation that all future scientists should be able to make in publications of work that involve research in this area.

In the Yili terrane at Awulale mountain, most shoshonitic lavas are related to post-collision extension and were extruded during the Late Carboniferous to Early Permian (310–280 Ma). Herein, we evaluate a small-volume occurrence of shoshonitic magmas in the southern Yili terrane formed c. 346 Ma ago. The high MgO (Mg#) and positive Hf isotope values of the shoshonitic magmas indicate the input of juvenile mantle-derived material. Still, their high Ba–Sr signatures were likely inherited from the partial melting of previously metasomatized lithospheric mantle. We argue the shoshonitic magmatic activity recorded a syn-subduction extensional history in the Yili terrane. This interpretation is consistent with the magmatic records from Early Carboniferous A-type granite and magnesian andesite found in the Zhaosu–Adentao–Dahalajunshan area of the southern Yili terrane. Combined with the geological development in this area, we propose that the emergence of the shoshonitic rocks records either the retreat of the trench or the rollback of the Junggar oceanic slab that occurred at or before the 346.1 ± 3.1 Ma age of the rocks.

The Almogholagh–Dehgolan region is in the North Sanandaj–Sirjan zone of NW Iran. The granites of the region are metaluminous and display geochemical and textural characteristics of transitional granites between ferroan (A-type) and I-type granites. In geotectonic discrimination diagrams, the Almogholagh–Dehgolan granites plot mainly in the fields of within-plate granites and volcanic arc granites. With the exception of the Qalaylan granites, parts of other granites resemble A2-type granites. Granites of the Qalaylan intrusive body have petrographic and geochemical features close to I-type granites and are not A-type. Primary mantle and chondrite-normalized spider diagrams show enrichments in light rare earth elements relative to heavy rare earth elements. For an age of 150 Ma, the initial 87Sr/86Sr and 143Nd/144Nd ratios vary from 0.702769 to 0.706545 and from 0.512431 to 0.512558, respectively. Epsilon Nd values vary in a relatively limited range between −0.3 and +2.2, which corresponds to a mixed mantle–crustal source. On the basis of new geochemical and isotopic data, we suggest a geodynamic model involving partial melting of lower crustal rocks with the contribution of mantle magmas in a weakly extensional tectonic setting for the generation of the A-type granites of the region. The occurrence of ferroan (A-type) granites in this region of the Sanandaj–Sirjan zone indicates the existence of a partly extensional tectonic environment in a mainly compressional subduction-related regime in Late Jurassic time.

The rock record from the late Early Jurassic in southern Africa encompasses the history of voluminous continental flood basalt outpourings associated with the magmatic events in the Karoo–Ferrar Large Igneous Province (LIP) in southern and eastern Gondwana. This multiphase magmatism produced one of Earth’s largest continental flood basalt successions volumetrically and is assumed to have been a main driving mechanism in late Early Jurassic global environmental perturbations, including mass extinctions and changes in climate. In southern Africa, these Lower Jurassic flood basalts are interbedded with fossiliferous sedimentary rocks, which in turn host the last signs of ‘Karoo life’ in the form of fossil plants, invertebrates and vertebrates, including the trackways of hopping mammals and the ultimate Karoo dinosaurs. The sedimentology and palaeontology of the interbeds archived depositional and biotic processes in running water as well as in and around shallow, up to ∼10 m deep freshwater lakes and ponds in the late Early Jurassic. This study explains how a complex freshwater palaeo-habitat prevailed – albeit temporarily – in this extremely stressful environment, which was unlike any modern volcanic system. The evidence collectively points to seasonally wet, warm temperate climatic conditions during the early phases of Karoo volcanism. Moreover, the evidence in the rocks also suggests that the dynamic volcanic conditions resulted in shifting habitats that likely facilitated the migration of the ultimate Karoo biota towards the north and west, away from the main Karoo land of fire, just before Gondwana started to disassemble. This refinement of the environmental dynamics in southern Gondwana presented herein lays the groundwork for future high-resolution volcanological, geochronological and chemostratigraphical studies aimed at the nuanced understanding of the global environmental effect of the Karoo–Ferrar LIP.

The Drewer quarry located in the Rhenish Massif is a well-studied outcrop that comprises Upper Devonian (Famennian) to Lower Carboniferous (Viséan) strata. Within the Drewer deposits two black shale intervals have been described that are linked to two global oceanic anoxic events, the Hangenberg Event and the Lower Alum Shale Event. The black shales associated with the Middle Tournaisian Lower Alum Shale Event contain abundant phosphatic concretions, which were investigated using thin section petrography, powder X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The concretions formed during several growth phases under anoxic and at least episodically sulphidic conditions within the sediment and served as a substrate for subsurface microbial mats that formed phosphatic microstromatolites. The microstromatolites occur either as partially branched columns of up to 600 µm in length attached to the phosphatic concretions or as smaller, bulbous aggregates surrounding the concretions. Element mapping identified the presence of pyrite and other metal sulphides within the phosphatic microstromatolites. The carbon and oxygen stable isotopic composition of phosphate-associated carbonate within the phosphatic microstromatolites suggests that the mat-forming microorganisms were probably anaerobic, chemotrophic microbial communities dwelling in the anoxic environment during the Lower Alum Shale Event. Such interpretation agrees with the deeper-water depositional setting of the Lower Alum Black Shale and its high content of organic matter, suggesting that chemotrophic microbial mats are potent agents of phosphogenesis in general, and of the formation of phosphatic stromatolites in particular.

Thrombolite reefs with archaeocyaths are common in the subtidal limestones of the lower Cambrian in the western Anti-Atlas of Morocco. The Igoudine Formation of the Tata Group recorded the first replacement of the microbial consortium (stromatolite-dominated) by thrombolite reefs with archaeocyaths and shelly metazoans. In order to better understand the role of the microbial community in the formation of thrombolite reefs with archaeocyaths across this critical transition, the macro-, micro- and ultra-fabric of thrombolites have been studied in detail. Three major components are identified within the first thrombolytic reef: archaeocyaths, calcimicrobes and micritic matrix. The studied thrombolites are typically dominated by the calcimicrobe Renalcis with subordinate Epiphyton and Girvanella. Scanning electron microscopy of the dark micrite of the Renalcis chambers showed amorphous translucent sheet-like structures interpreted as extracellular polymeric substances, closely associated with organominerals including nanoglobules and polyhedrons. Exceptionally well-preserved Renalcis chambers contain bacterial fossils similar to those described in modern microbialites, including microspherical coccoid fossils and filamentous bacteria that are either spaced or in close associations forming colonies. These organomineralization-related features suggest a bacterial origin for the Renalcis calcimicrobe. The matrices between the Renalcis chambers consist predominantly of clotted peloidal micrite. Mineralization of Renalcis microframes may involve two major biomineralization processes: (1) replacement of organic matter by organominerals resulting from anaerobic degradation of extracellular polymeric substances and bacterial sheaths and (2) encrustation of bacterial sheaths and extracellular polymeric substances due to increasing alkalinity of the microenvironment. These mechanisms played a crucial role in the early diagenetic cementation and preservation of the studied reefs.

A remarkable specimen of the actinopterygian fish Pachycormus macropterus from the Early Jurassic (Toarcian) Posidonienschiefer Formation of Germany exceptionally preserves an unusually large ammonite inside its gut. The ammonite was swallowed by the fish, likely by accident, and represents the first direct evidence for an actinopterygian fish consuming an ammonoid. Exceptional aragonite preservation of the conch retaining partial nacreous lustre, combined with only minor acid etching of the shell, strongly indicates that the ammonite was ingested immediately prior to and was directly responsible for the fish’s death. The fish’s stomach provided a microenvironment protecting the aragonite from chemical dissolution.

We investigate the shape and strength of the magnetic fabrics (anisotropy of magnetic susceptibility (AMS) data) of various massive granitic plutons from different parts of India, using the eigenvalue method. The study aims to analyse eigenvalues and establish their relationship with various deformational attributes. It involves: (1) calculating eigenvectors and their corresponding eigenvalues from magnetic fabric datasets; (2) finding a link between the geometrical appearance of eigenvectors and the mechanistic issues involved with a specific deformation scenario; and (3) determining shape and strength parameters from the magnetic foliation data distribution.

The statistical analysis for the unimodal magnetic fabric dataset of orthorhombic symmetry class implies that the plane, consisting of intermediate (V2) and minimum (V3) eigenvectors with pole V1, accurately traces the instantaneous stretching axis (ISAmax) of a particular material flow system under a pure shear regime. Moreover, for the distributions of similar symmetry and modality, we infer that the rotational characteristics of eigenvectors with respect to a fixed coordinate cause a distinct shift of such planes (V2–V3) from the ISAmax of a steady-state flow system under simple shear, where a substantial amount of rotational strain is involved. However, our findings also suggest that variation in symmetry and modality of magnetic fabric data distribution of different studied granitoids can directly influence the relative disposition of V2–V3 with respect to the direction of ISAmax. We conclude that eigenvalue analysis of magnetic fabrics is a powerful approach, which can be utilized while studying the salient deformational aspects of any syntectonic massive granitic body.

The traces left by earthquakes in the unlithified sediments, recorded as soft-sediment deformation structures (SSDS), are well reconstructed as palaeo-seismic signals, while the origin of SSDS, seismic vs. Aseismic, is challenging. The present study discusses the origin of SSDS and its implications on palaeoceanography and sediment architecture. In the Middle Jurassic succession of Spiti Himalayan region in India, the topmost part of the Ferruginous Oolitic Formation (FOF) consists of four layers of SSDS and is underlain by the lower member of the Spiti Formation (SF). The sedimentary facies analysis documents the palaeogeographic shift from the middle shelf (carbonate-shale repository: FOF) to the outer shelf (black shale: lower member of SF). The SSDS layers, exhibiting load casts, ball and pillow structures, indicate gravitational instability, while syn-sedimentary faults and insitu breccia are the results of brittle deformation. The dominance of storms in depositional sites often argues for a possible triggering agent for SSDS. Therefore, it was necessary to distinguish between seismic vs. aseismic triggering agents. The lateral continuity, vertical repetition, confinement of SSDS at the top part of FOF and sharp change of facies assemblage indicate seismicity-induced syn-sediment deformation, i.e. seismite. The transition from middle shelf to outer shelf at the onset of seismite indicates that seismic impact possibly caused the rapid subsidence, resulting in the palaeogeographic shift. The rapid transgression is recorded as carbonate-shale repository to anoxic black shale. This study highlights the importance of sedimentological analysis to distinguish the seismite and its implications on palaeogeographic evolution and sedimentary architecture.