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Identification of the processes producing soft‐sediment deformation structures, common in siliciclastic deposits and less abundant in carbonate successions, is complex, because different processes may produce similar structures. Thus, interpreting the origin of these structures may be challenging: it requires both a detailed sedimentological study, and the knowledge of the depositional environment and stratigraphic evolution, in order to provide hints to identify the processes affecting sediments after deposition. Among the potential causes of the formation of soft‐sediment deformation structures, seismic shock is one of the possibilities, but their origin could be also related to other triggering mechanisms, such as volcanic activity, sediment loading, salt tectonics, fluid expulsion, meteorite impacts and mass movements. Although it is a plausible option, the interpretation of these structures as 'seismites' is not obvious: it must be supported by different lines of evidence, considering that the correct interpretation of soft‐sediment deformation structures as a consequence of seismic shocks acquires important implications in palaeoseismology studies. The occurrence of diverse soft‐sediment deformation structures in a fault‐controlled basin (i.e. in a geological setting characterized by syndepositional tectonics) preserved in different subenvironments of a Norian carbonate system in the Southern Alps of Italy provides the chance to characterize different types of soft‐sediment deformation structures along a platform‐to‐basin depositional profile. Presence of pseudonodules in basinal resedimented limestone, sedimentary dykes and clinostratified breccias with unlithified clasts in slope settings and liquefaction of inner platform facies at the platform top testify to an origin compatible with multiple seismic shocks, repetitively affecting the same stratigraphic intervals. The diverse types of soft‐sediment deformation structures in the studied carbonate system provide a rich catalogue of structures related to seismic shocks, representing a possible reference for other similar settings. [ABSTRACT FROM AUTHOR]

Upper Palaeozoic lacustrine basin deposits not only record local tectonism but are also an archive to evaluate global palaeoclimate changes linked to the Late Palaeozoic Gondwanan ice age. The Tournaisian Horton Group of Nova Scotia, south‐east Canada, accumulated in rift basins following the final accretion of peri‐Gondwanan terranes to the Appalachians. Sedimentology, mineralogy and geochemistry of the well‐exposed sandstones and shales at the classic Blue Beach section (ca 353.5 to 352 Ma) reveal the interplay of local tectonism and global climatic controls on lacustrine sedimentation. The lacustrine depositional environment gradually transitioned from deep water offshore at the base of the section to wave‐dominated and fluvial‐dominated nearshore at the top. Multiple small transgressive–regressive sedimentation cycles have an average 21 ka duration, likely related to Milankovitch cyclicity. Unusually abundant soft‐sediment deformation structures and landslides are the sedimentary responses to frequent earthquakes during the most active phase of rift subsidence. The overall succession shows changes from a shallowing‐up balanced‐filled to an overfilled lacustrine basin. The chemical weathering intensity index and the Th/K ratio show a longer‐term trend from dry and cool conditions low in the section to humid and warm conditions near the top, with rapid change in the transition period. The section records the peak of the global mid‐Tournaisian carbon isotope excursion and the corresponding cooling event (354 Ma to approximately 351 Ma). The sedimentary succession is a response to long‐term and short‐term climatic cycles influencing lake level and sediment supply during the time of maximum rift basin subsidence recorded by the soft‐sediment deformation structures. [ABSTRACT FROM AUTHOR]

To assess the regional seismicity during the late Quaternary, we studied a well−exposed sequence of Luobozhai lacustrine sediments, 14.5 m thick, near Lake Diexi in the upper reaches of the Minjiang River, eastern Tibetan Plateau. High-resolution geochemical, grain-size, and magnetic susceptibility indicators were then used to obtain a continuous record of the changes in elemental and physical properties within the profile to determine additional seismic events that did not result in soft sediment deformation structures. Rapidly deposited layers with underlying soft sediment deformation structures in the Luobozhai section indicate 18 siliciclastic-enriched sandy sediment fluxes from earthquake-triggered landslides or dust of siliciclastic-enriched clastic materials; isolated rapidly deposited layers (without underlying soft sediment deformation structures) record 17 additional earthquake-induced inputs of detrital material into the lake. Hence, there are a total of 35 seismic events (M ≥ 5.0) recorded within the Luobozhai section, which probably reflects the frequent seismicity of Minjiang fault. Optically stimulated luminescence and 14C dating of the Luobozhai section indicates continuous sediment deposition from 18 to 10.2 ka, and had a mean recurrence interval of approximately 224 years. Heavy mineral analysis shows that event layers and non-event layers have different mineral compositions. This reflects changes in sedimentation pre, during, and post a seismic event, especially the co-seismic debris material (e.g., from landslides and/or dust storms) that controls changes in provenance within the drainage basin, and in turn affects the regional erosion rate and weathering patterns. This study opens up new avenues of paleo-earthquake research. [ABSTRACT FROM AUTHOR]

The complexity of subglacial till sedimentology is discussed at the microscale to develop a revised model of microstructure evolution and development in subglacial tills. Mapped thin sections from the Northwest Territories and southern Ontario, Canada reveal a myriad of microstructures. Discussion of the relevance and meaning of these microstructures leads to a new revised model of subglacial soft sediment deformation to account for the development and evolution of these microstructures. The model is time-transgressive such that over time both pervasive and non-pervasive deformation conditions persist repetitively within the subglacial till environment under mixed rheologies. Microstructure types appear to be sequential in development and, during progression, are partially or wholly overprinted, destroyed, rotated, and suffer further subsequent deformation, or remain intact but intercalated with structures of other later or earlier deformation phases. This new revised model helps explain that the vagaries of till microsedimentology can be accounted for and, in most instances, predicted. [ABSTRACT FROM AUTHOR]

The susceptibility of grains in sediment to the liquefaction process causes the development of deformation structures. Some sediments undergo liquefaction, others do not. There is a group of sediments especially prone to liquefaction, which was proven during laboratory experiments. However, the field results are often slightly different from those obtained experimentally because of many unpredictable factors influencing the course of the liquefaction process. For this reason, we tested 144 samples of unconsolidated Quaternary‐age sediments, collected from eight study sites in Germany, Lithuania and Latvia, which have been liquefied. We also present some new dating results. These samples were divided into two groups of soft‐sediment deformation structures: concave up (e.g., injection structures) and concave down (e.g., load casts, pseudonodules). The granulometry of all deformation types was statistically evaluated, which allowed identifying textural differences between sediment contained in concave up and concave down structures. We suggest that the mobilization of silt fraction is responsible for the further deforming process. We also confirm that the maximum content of clay in sediment prone to liquefaction cannot exceed 14%, but only with a significant content of coarser fractions (silt and sand). Moreover, we identified two separate zones of the specific grain size in which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third "transitional zone" where all forms occur. The "transitional zone" is separated from the concave up structures and concave down structures zones by two "gap zones" in which no liquefied sediments were observed. Plain Language Summary: Liquefaction is a process of temporary loss of shear strength of water‐saturated sediments, during which the solid‐state sediment behaves like a plastic mass or a viscous solid. It can be triggered in natural conditions by numerous factors, including waving, rapid sedimentation, earthquakes and the fall of meteorites. Sandy silt and silty sand are commonly known as the most liquefaction‐prone sediments, but the specific granulometric features are still insufficiently characterized. We analyzed 144 samples of unconsolidated Quaternary‐age sediments deposited in lacustrine, shallow marine and fluvial environments, which were liquefied. We divided all liquefaction‐induced soft‐sediment deformation structures into active and passive concave up (e.g., injection structures) and active and passive concave down (e.g., load structures). As a result of statistical tests, provided for each group separately, we observed that the silt content is the main factor for sediment deformation processes initiating the further development of all deformation structures. On the basis of grain‐size composition of liquefied sediments, we also identified two separate zones for which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third "transitional zone" where all forms occur. These zones are separated by two "gap zones," where no liquefied sediments were observed. Key Points: Liquefaction‐induced soft‐sediment deformation structures were divided into active and passive concave up structures and active and passive concave down structuresContent of silt is the main factor for deformation processes initiating the further development of all deformation structuresConcave up structures zone, concave down structures zone and transitional zone were distinguished on the basis of grain‐size composition of liquefied sediments [ABSTRACT FROM AUTHOR]

Kefalonia Island is situated in western Greece and geologically corresponds to the Apulian Platform Margins (APM), with the Apulian Platform lying to the west and the Ionian Basin to the east. The studied deposits, with a thickness up to 164.5, extend along the 650 m long Agia Efimia bay, ranging from the Middle Paleocene (Selandian) to the uppermost Eocene (Priabonian), during the latest part of the rift stage. Fieldwork measurements of soft-sediment deformation structures (SSDS), paleocurrent directions, the size and abundance of siliceous concretions (SC) and siliceous beds (SB), and shale horizons were correlated with the age of selected samples, and thus, the relation of the tectonic regime with the depositional conditions was presented. As SSDS could represent an indicator of tectonic activity and instability of the basin floor instability, the size and the abundance of the SSDS whereas used to identify the parameters that produced the basin floor instability like the intensity of tectonic activity. The studied section, with a general NE-SW orientation, was subdivided into five (5) different units. The changes of these units in paleocurrent directions, the size, the abundance, and the thickness of SSDS, SC, and SB and the presence of shale horizons in the upper unit, characterize a gradual change of the depositional conditions in the APM, from the Upper Paleocene (Selandian) to the Upper Eocene (Priabonian). The factor that influenced the abovementioned changes was related with the presence and the activity of normal faults that produced instability of the basin floor. Therefore, a reduction in tectonic activity from the Paleocene to the Eocene is suggested. [ABSTRACT FROM AUTHOR]

To promote oil and gas exploration of the Carboniferous formation in the Shibei sag, the northeastern margin of Junggar Basin, recently drilled rocks from Well ZB6 with typical seismics were characterized. Through systematic core observation, the identification marks of seismites were described, a vertical sequence of seismites was established, and its oil and gas geological significance was analyzed. The results show that the seismites have typical identification marks, such as soft-sediment deformation structures (including five typical marks: liquefied stone vein, liquefied crinkled deformation structure, ball–pillow structure, flame structure and load cast, water release structure and liquefied breccia), brittle fracture structures (including three typical marks: seismic fractures, synsedimentary microfractures and seismic fracture rock) and special rock types, such as seismic grain-supported conglomerates. The stratigraphic succession reconstructed in Well ZB6 was characterized, from base to top, by (1) a basal non-seismic interval; (2) a seismic interval made up of a grain-supported conglomerate level, brittle fracture level, soft-sediment deformation level; and (3) a non-seismic interval. The discovery of seismites has oil and gas geological significance for improving reservoir performance and forming favorable source–reservoir–cap assemblages. The research describes the new reservoir genetic type and exploration direction of the Carboniferous formation in the Shibei sag (China), which has important guiding significance for the next step of oil and gas exploration. [ABSTRACT FROM AUTHOR]

In this study the types and forms of soft-sediment deformed in storm beds and related sediments of the Upper Devonian of the southern Cantabrian Mountains are investigated, as well as their possible genetic processes. The storm bed successions consist of very thin to medium bedded tempestites, indicating an almost equilibrium in which a more or less constant bathymetry was maintained over a long period, with a consistent unidirectionally downwelling storm flow transport in response to coastal setup, perpendicular to the E-W running palaeoshoreline. The soft-sediment deformed storm beds are not spread equally across the Upper Devonian succession, but occur in specific stratigraphic horizons. Based on their forms, shapes, and stratigraphic relation with overlying and underlying strata, they can be grouped into five types, each associated to deformation processes which act in specific parts of the depositional profile of the Late Devonian coastal zone: (1) the chaotic contorted and folded mixture of very fine-grained sand, sandy mud, and mud (Complex mixture), (2) the folded very fine-grained sandstone beds (Folded sandstone), (3) the faulted and folded silty shales, with folded sandstone beds, and lithoclasts (Muddy debris), (4) the folded sandstone beds with brittle-ductile deformed shear zones and imbricated toes (Sand flow rolls), and (5) the ball-like bodies of sandstone with internal lamination and upcurled edges (Pseudonodules). The depositional mechanisms of tempestite sand-mud layers contain several soft-sediment deformation driving forces and agents. The geological data of the deformed bedforms does not point to a single deformational cause. The various deformation processes involved act simultaneously or as successive events. The overall characteristics of the soft sediment deformation types are (1) a storm bedded succession of the transition zone, (2) or a storm bedded-related succession of the offshore zone, (3) a steep depositional slope and, (4) a tectonical active area, probably with earthquakes. [ABSTRACT FROM AUTHOR]

This paper describes various soft-sediment deformation structures present in the Triassic deposits of the Betic External Zone (Southern Iberian). These structures, together with variations in deposit thicknesses, internal angular unconformities, and synsedimentary faults, point to intense tectonic activity from the Middle to Late Triassic related to a stage of rifting. The Middle–Late Triassic in the Betic External Zone shows a sedimentary record represented by Muschelkalk and Keuper facies. In the Ladinian Muschelkalk, carbonates appear slumps, breccias, load casts, slide and parallel shear surfaces, and tsunamites. In the sandstones of the Carnian Keuper facies, different seismite beds and ball and pillow structures can be discerned. Above these deposits, the carbonate Zamoranos Formation of the Rhaetian displays volcaniclastic rocks with conglomerates, slumps and synsedimentary faults. All these features and magmatism suggest some tectonic activity, possibly related to the breakup of Pangaea, especially at the end Triassic. We highlight the features that indicate this tectonic activity over time and discuss the factors that triggered the development of these structures, along with the conditions that made this possible.

Soft-sediment deformation structures play an important role in interpreting regional tectonics and basin evolution during slumping events. The Satpura Basin is interpreted as pull-apart with a monoclinal northerly palaeoslope throughout its evolution. The basin formed as a result of sinistral strike-slip faulting, induced by the ENE–WSW-trending Son-Narmada South fault in the north and the Tapti North fault in the south. We have analysed the slump folds within the basalmost Talchir Formation and related these to regional tectonics and palaeoslope changes in the Satpura Basin. The glaciofluvial strata of the Talchir Formation, exposed in the southern part of the Satpura Basin, record intricacies of folds created during slumping. Several fold styles can be distinguished, within alternations of competent sandstone and incompetent shale layers, some of which indicate buckling. Upright folds, resulting from pure shear, underwent rotation of their axial planes and fold axes during simple shear-dominated progressive deformation when the slump moved downslope. The soft-sediment deformation structures that we have studied show refolding patterns that closely resemble comparable folds known from lithified rocks. These layers with refolded structures are overlain by unde-formed sediments, which proves that they are the product of a single ongoing slumping process, rather than of successive deformation events. Our analysis of their fold axes and axial planes, together with fold vergences and thrust directions within the slumps, suggests a mean slumping direction towards the southwest. Analyses of slump folds and their relationship with regional tectonics have allowed us to reinterpret basin evolution history. The southwesterly trending palaeoslope of the basin suggest that the slope of the basin was not uniform throughout its evolution. At the opening, the oblique slip fault, which trended NE–SW, generated due to movement along the ENE–WSW basin bounding faults, was more active and triggered slumping event within the Talchir deposits in the basin. With progressive overlapping of the basin-bounding faults, the Satpura Basin gradually tilted towards the north.

The occurrence of soft-sediment deformation structures (SSDS) have long been recognized in several types of sedimentary environments and deposits. However, their presence in contourite drift deposits is still unreported in the literature. In this work, we present the first detailed description of SSDS found within the Pliocene sedimentary record of the Faro Drift, recovered during the Integrated Ocean Drilling Program (IODP) Expedition 339. The Faro Drift is the largest contourite drift of the Contourite Drift Depositional System developed in the Gulf of Cadiz since the Late Miocene by the circulation of the Mediterranean Outflow Water. The SSDS were identified in archive-halves of core sections located between ∼458 and ∼ 510 m below seafloor (mbsf) (hole U1386C), and between ∼599 and ∼ 670 mbsf (hole U1387C). Their identification and characterization was made by visual core description, structural geometrical analysis in core-scan high-resolution images, and scanning electron microcopy (SEM) analysis in selected intervals. The SSDS were classified based on the exhibited geometry, structural configuration and respective kinematics. The main deformation process and potential trigger were inferred from the geometrical and kinematics analysis. We identified five categories of SSDS: i) microfaults (normal and thrust faults), ii) slump sheet (formed by several types of folds, such as eye-folds, fish-hook folds, spiral folds), iii) convolute bedding, iv) folds within debrite mudclasts', and v) sigmoidal-like structures. Although the first three are well known types of SSDS, the folds within debrite mudclasts' and sigmoid-like structures have been scarcely recognized and described at core-scale. The inferred deformation processes responsible for the formation of these SSDS were i) brittle deformation by hydrofracturing and compaction faulting (microfaults), ii) hydroplastic (ductile) deformation (slump folds, folds within debrite mudclasts'), iii) liquefaction (convolute bedding), iv) shearing by flow movement (sigmoid-like structures). The most probable triggering agents seem to have been overloading, downslope movement of slump sheet and debris flow, and shearing by currents. • Soft-sediment deformation structures identified for the first time in contourites. • Structures formed by hydrofracturing, hydroplastic deformation, liquefaction, shear. • Overloading and shear by flow movement have been as the main potential triggers. [ABSTRACT FROM AUTHOR]

Late Pleistocene glaciolacustrine sediments in the northern part of Estonia show a wide spectrum of ductile and brittle deformation structures like: (1) injection structures, dish structures, load casts, pseudonodules, ball-and-pillow structures, flame structures and fragments of broken-up sandy laminae all occurring in three internally deformed layers separated by undeformed layers, (2) large-scale upright gentle folds of outcrop size, (3) faults and fractures, and (4) water-escape structures (hydrofractures). We investigate the potential trigger mechanisms for the development of these deformation structures, their relationship in space and time as well as the lithological and geometrical features of soft-sediment deformation structures necessary to recognise deformation mechanisms. Based on comprehensive geological and numerical investigations, we link their origin to two major processes: (1) glacial rebound of Earth's crust causing earthquakes and (2) proglacial and submarginal glaciotectonic processes related to local oscillation of the ice-sheet front. We suggest criteria which allow us to recognise these two trigger mechanisms and propose a new proxy for reconstructing glacigenic processes and environments based on recognised soft-sediment deformation structures and their interrelationships. Our findings also highlight the significance of water saturation levels in glacigenic sediments and their impact on deformation processes. Furthermore, we introduce new types of water-escape structures that develop in proglacial marginal and/or submarginal settings. Our results contribute to a more nuanced interpretation of glacial activity and environmental conditions during the Late Pleistocene period in the study area. • Deformation processes: (1) Glacial rebound causing earthquakes, (2) Proglacial and submarginal glaciotectonic activities. • The significance of water saturation levels in glacigenic sediments and their impact on deformation processes. • Discovery of new types of water-escape structures that develop in proglacial marginal and/or submarginal settings. • First-time modelling of glacially induced Coulomb failure stress changes in Estonia around 14 ka. [ABSTRACT FROM AUTHOR]

Subaqueous mass‐transport processes are one of the mechanisms for transport of sediment into the deep sea. Internal structures and depositional processes of carbonate mass‐transport deposits are relatively poorly understood relative to siliciclastic facies due to their comparative paucity in the rock record. A variety of carbonate mass‐transport deposits, including slumps, debrites and deep‐channel‐confined density flow deposits, occur in Middle–Upper Ordovician slope deposits in western Inner Mongolia (Wuhai), China. These provide a rare opportunity to illustrate the emplacement history of carbonate mass‐transport deposits at the outcrop scale. The slumps and debrites host remarkable folds, chaotic beds and imbricated beds that reflect differences in both rheology and position on the slope. Individual slump sheets show gradations between undulating laminae, inclined and recumbent folds, highly deformed folds, and chaotic textures upslope from the toe region. Debrites are commonly interbedded with slump deposits, whereas imbricated beds are present in the middle and lower parts of the toes of slump sheets near the terminal wall. In the study area, thin‐bedded limestone with slump deposits of the Kelimoli Formation are overlain by fine‐grained, siliciclastic‐dominated, slope deposits of the Wulalike Formation. A thick breccia of the Wulalike Formation was deposited in a main feeder channel in south‐east Wuhai, but to the west‐north‐west the breccia was deposited in distributary channels possibly represented as a unique lower‐slope pattern of gullies. At the latter locality, the breccia was deposited solely within the channels on a steep west‐north‐west dipping slope under density‐driven flows. The mass‐transport deposits documented herein records passive to foreland basin tectonic transitions, and associated platform foundering and steepening of the slope. A slope facies model was constructed to demonstrate the spatial and temporal variations of mass‐transport deposits during basin evolution, and as such it provides a template for the interpretation of the deposits of ancient slopes that underwent passive to active tectonic transitions. [ABSTRACT FROM AUTHOR]

Liquefaction can cause deformation of unconsolidated sediment, but specific processes involved and the trigger mechanisms often remain obscured. This study describes multiple deformed sediment layers in a succession of lacustrine sand, silt and clay deposited during the Marine Isotope Stage 5d in north‐western Lithuania. The deformation structures (load casts, pseudonodules, ball‐and‐pillow structures, broken‐up laminae and injections) are embedded in ten separate layers of fine‐grained, laterally continuous sediments. Detailed mesoscale sedimentological analyses suggest that each deformation event consisted of numerous successive stages of sediment advection facilitated by liquefaction. Low‐permeability fine‐grained laminae contributed to localized pore‐water pressure build‐up and lowering of sediment strength. Erosional top surfaces that truncate layers with soft‐sediment deformation structures suggest that at least seven deformation events were separated by successive periods of initial erosion and then uninterrupted deposition in the lake. The most likely trigger of the deformation was recurrent palaeoseismic activity possibly linked to a late glacial isostatic adjustment following the Scandinavian Ice Sheet melting after the Saalian glaciation. This study emphasizes the potential role of seismic processes in shaping the sedimentary record of the intraplate region of north‐eastern Europe and contributes to constraining the depth of liquefaction, regardless of the actual trigger mechanism. [ABSTRACT FROM AUTHOR]

Abstract An earthquake of magnitude M5.7 occurred in Yamutu village, Songyuan City, Jilin Province, NE China (45°16′12″N/124°42′35″E) on May 28, 2018, with a focal depth of 13 km. The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault, Second Songhua River Fault and Fuyu North Fault which lies northwest of Tancheng-Lujiang Fault (Tan-Lu Fault). The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter, caused serious disasters to the local surroundings. The visible liquefied structures include sand volcanoes, liquefied sand mounds, sand dikes and sand sills. Sand volcanoes can be divided into sand volcano with a crater, sand volcano without a crater and water volcano (no sand). Other soft-sediment deformation structures (SSDS) induced by the earthquake include deformation lamination, load and flame structures, deformation folds, dish structures, convolute bedding and water-escape structures. The formation process of the sand volcanoes comprises three stages: (1) building up excess pore-fluid pressure in the liquefied layer, (2) cracking of the low-permeable overlying layer, and (3) mixture of sand-water venting out of the ground surface. During the upward movement, the liquefied sand is injected into the low-permeable layer to form sand veins, sand sills and various types of deformation structures. Vertical distribution of seismic liquefaction structure can be divided into four zones: the thoroughly liquefied zone, the lower liquefied zone with SSDS, the upper liquefied zone with SSDS, and the ground surface liquefied zone. The liquefaction occurred at a burial depth of 2–5 m, and the thickness of liquefied sand is 2 m. NE-SW (35°–215°) trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault (Fuyu/Songyuan-Zhaodong Fault) to reactivate. The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disaster-prone areas. Meanwhile it provides abundant basic material for studying earthquake-induced SSDS in both ancient and modern sediments. The research is obviously of great significance to reveal that the northern Tan-Lu Fault has entered a stage of active seismic activity since the twenty-first century.

To promote oil and gas exploration of the Carboniferous formation in the Shibei sag, the northeastern margin of Junggar Basin, recently drilled rocks from Well ZB6 with typical seismics were characterized. Through systematic core observation, the identification marks of seismites were described, a vertical sequence of seismites was established, and its oil and gas geological significance was analyzed. The results show that the seismites have typical identification marks, such as soft-sediment deformation structures (including five typical marks: liquefied stone vein, liquefied crinkled deformation structure, ball–pillow structure, flame structure and load cast, water release structure and liquefied breccia), brittle fracture structures (including three typical marks: seismic fractures, synsedimentary microfractures and seismic fracture rock) and special rock types, such as seismic grain-supported conglomerates. The stratigraphic succession reconstructed in Well ZB6 was characterized, from base to top, by (1) a basal non-seismic interval; (2) a seismic interval made up of a grain-supported conglomerate level, brittle fracture level, soft-sediment deformation level; and (3) a non-seismic interval. The discovery of seismites has oil and gas geological significance for improving reservoir performance and forming favorable source–reservoir–cap assemblages. The research describes the new reservoir genetic type and exploration direction of the Carboniferous formation in the Shibei sag (China), which has important guiding significance for the next step of oil and gas exploration.

We analyze the evolution of the undeformed Middle to Late Pleistocene deposits of Es Codolar (Southern Eivissa, Western Mediterranean). The outcrop records a succession characterized by the alternation of aeolian, colluvial and alluvial fan deposits and palaeosols that result in a complex stratigraphic architecture. In this area, aeolian beds, colluvial deposits and palaeosols are exposed along sea-cliffs for almost 500 m, allowing detailed descriptions both of the general sedimentological and geomorphological features of the Middle to Late Pleistocene deposits. Several different types of soft-sediment deformation structures are described (load-casts structures, injection structures, water-scape structures, rizoconcretions), which will help us in the understanding of the climatic evolution and the syn- post-depositional processes. In this way, main processes triggering the formation of these structures seem to be sea level changes together with a wetter environment during warmer climatic episodes. [ABSTRACT FROM AUTHOR]

In order to clarify the genesis of liquefaction folds (convolutions) developed at lithological boundaries in lacustrine sediments, such structures in three regions were compared. Folds in each region differ in morphology, composition of sediments, and the vertical gradient of their density and viscosity upon deformation. It is proposed to use the ratio of the widths of syn- and anticlinal folds in the convolution horizon (Ks) to analyze the latter, in which Ks > 1 corresponds to the normal viscosity gradient, and Ks < 1, to its inversion. Convolutions of the Baltic Shield and Yakutia from Ks ≥ 1 are noted in the most liquefied sediments with unstable density stratification (sands-on-silts), which indicates the possibility of their spontaneous formation during lithogenesis. Folds with Ks ≈ 1 are widespread in Yakutia, which indicates their cryogenic genesis. Convolutions in the Tien Shan were formed with stable sediment stratification in terms of density (silts-on-sands); low-fluidized coarse-grained sediments with viscosity inversion were also involved in deformation. These features indicate the seismic initiation of liquefaction processes. The results substantiate the lithogenic genesis of convolutions in lacustrine complexes of the Baltic Shield, cryogenic and lithogenic in Yakutia, and seismogenic in the Tien Shan. It is proposed to determine the scatter of the Ks value in the diagrams for diagnosing the genesis of convolutions. For lithogenic structures, this parameter is shifted to the region with Ks > 1, and for seismites, it is relatively symmetric with respect to Ks = 1. [ABSTRACT FROM AUTHOR]

Three (3) outcrops belonging to the Pedawan Formation found along Jambusan-Semadang Road in the Siburan area are characterized by well-developed soft-sediment deformation structures (SSDS). SSSD is formed due to instability, which possibly results from factors like rapid sedimentation, overloading, or earthquake. The SSDS in Siburan, in the form of folded and faulted structures, were recorded within thick sequences of mud-dominated turbidites of the Pedawan Formation (Jurassic -- Cretaceous age). These SSDS are grouped into five (5) different types, which are 1) mud-dominated slumped structures, 2) folded and overturned sandstone beds, 3) contorted argillaceous mudstone beds, 4) sandstone boulder, and 5) envelope structure. The small-scale SSDS (<1 m), like localized slumps and envelope structure, are interpreted to have formed due to overloading and rapid deposition. The large SSDS (> 1 m), such as detached sandstone blocks, internal faulting, and folds, are attributed to movements related to earthquakes. [ABSTRACT FROM AUTHOR]

• XMCⅠ and XMCⅡ indicates continuous sediment deposition from 19.4-9.9 ka and 15.5-10.1 ka, respectively. • 30 seismic events recorded in Xinmocun section during 18.6-10 ka, with an apparent recurrence time of ~280 years. • The Diexi area has frequent seismic activity, with a high seismic risk in the future. Five M s 7.0 earthquakes (Wenchuan, Yushu, Lushan, Jiuzhaigou and Maudo) have occurred on the eastern Tibetan Plateau since 2008, and > 20 historical earthquakes (M s ≥ 5.0) have also been recorded, demonstrating the strong seismic activity prevalent in this region. Owing to the geomorphology of the region, consisting of alpine valleys with a lack of Quaternary deposits, it is difficult to conduct paleo-earthquake research through the excavation of trenches. Lacustrine sediments are regarded as the most suitable archives for paleo-earthquake studies because they often comprise a detailed, long-term, and continuous environmental record. To assess the seismic activity of the Diexi, we studied a well-exposed outcrop of Xinmocun lacustrine sediments that included three sections (XMCⅠ (11.5 m), XMCⅡ (5.6 m), and XMCⅢ (11 m)) near Diexi Lake, moving from a lake shore to lake center environment, at the intersection between the Minjiang fault and Songpinggou fault. Taking into account the geodynamic setting of the area and its known tectonic activity, soft-sediment deformation structures, including load and flame structures, injection structures, ball structures, pseudo-nodules, boudinage structures, plunged sediment mixture, liquefied breccia and micro-faults, discovered within the sections are interpreted as seismites. High-resolution grain-size and magnetic susceptibility indicators were used to obtain a continuous record of the changes in physical properties within the three sections enabling the recognition of additional seismic events that did not result in soft-sediment deformation structures. Rapidly deposited layers with underlying soft-sediment deformation structures in the sections record five (XMCI, XMCII and XMCIII) seismic events; these comprise siliciclastic-enriched sandy sediment fluxes from earthquake-triggered landslides or dust of siliciclastic-enriched clastic materials. Isolated rapidly deposited layers (without underlying soft-sediment deformation structures) record 18 (XMCII), 12 (XMCI), and 21 (XMCIII) additional earthquake-induced inputs of detrital material into the lake. Optically stimulated luminescence and 14C dating of the XMCⅠ, XMCⅡ, and XMCⅢ sections indicate continuous sediment deposition from 19.4–9.9 ka, 15.5–10.1 ka, and 18.7–10.6 ka, respectively, and the seismic events recorded in these sections can be cross-correlated within the age error range. Hence, there are a total of 30 seismic events recorded within the Xinmocun sediments during the period 18.6–10 ka, suggests a weakly periodic pattern with an apparent recurrence time of ∼ 280 years. The Minjiang fault and Songpinggou fault are Holocene active faults with a risk of causing strong earthquakes. Due to the Diexi area is located at the intersection of the Minjiang fault and Songpinggou fault, and has frequent seismic activity, suggest a high seismic risk in the future. [ABSTRACT FROM AUTHOR]

The Barra Velha Formation, an Aptian Pre-salt unit of the Santos Basin, southeastern Brazil, is well-known for containing an important hydrocarbon reservoir. In the Atapu field, the lower part of the formation consists of laminated lutite (carbonate, siliciclastic, and hybrid), microbialite, and tufa rocks. The succession records muddy and in situ carbonate deposition in a low energy and shallow alkaline lacustrine environment in an active rift basin. Millimeter to decimeter scale soft-sediment deformation structures, faults, and fractures are very frequent and recurrent along the lutite succession. Convolute folds, loop bedding, injectites, intraclastic breccia, diastasis cracks, and associated faults, record ductile-brittle deformation in semi-lithified sediments. Normal planar and listric faults and unconfined fractures register dominant brittle deformation in lithified sediment. Foliated cataclasite and rare reverse faults record downdip slip on the hanging wall of temporarily inactive listric faults. The set of structures, the geological model, and the absence of other evident trigger mechanisms indicate that both ductile and brittle deformation are related to seismic events. The soft-sediment deformation structures are interpreted as having evolved during seismic shaking, while foliated cataclasite probably registers inter-seismic creep deformation. • Deformational structures in the lower Barra Velha Formation, Aptian Pre-salt succession, Atapu field, Santos Basin, Brazil. • Soft-sediment deformation structures, faults, and fractures. • Ductile-brittle and brittle deformation in semi-lithified and lithified sediments. • Seismites and inter-seismic foliated cataclasite. [ABSTRACT FROM AUTHOR]

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This study is concentrated on distinguishing recently exposed seismically induced sediment structures from those created in non-seismic environments. Earthquake structures documented in Hamburg (NW Germany) primarily consist of compressional forms; less frequent are structures resulting from extensional or gravitational stress. The diverse styles of these seismic deformations can be attributed to different mechanisms, e.g. compression as a result of seismic shock or of sediment intrusion, liquefaction, fluidisation, loading, or shear stress, as well as volume loss and collapse following blowout activity. Originally described two-sided flames, sandwiched occurring interlocked flames, blossom-like seismites, specific diapirs and sediment intrusions (veils) are supposed to be indicative of a seismic genesis. [ABSTRACT FROM AUTHOR]

Abstract Soft-sediment deformation (SSD) structures are widespread in the sedimentary record, and numerous triggering mechanisms can induce its development, including glaciation, earthquakes, overloading, ground-water fluctuations, and wave movement. The Late Cretaceous Uberaba Formation preserves SSD structures as small- and large-scale load casts and associated flame structures, pseudonodules, and convolute laminations observed in the contact of three well-defined intervals among fine- to coarse-grained lithic and conglomeratic sandstone with fine-grained arkose and mudstone beds. Based on the morphology of the SSD structures, sedimentary facies of the Uberaba Formation, and similarities with previous observations in the geological record and laboratory models, these features are assigned to liquefaction-fluidization processes as the major deformational mechanism triggered by seismic and aseismic agents. We propose that a deformation occurred just after the sedimentation triggered by seismic shock waves and overloading, induced by the sudden deposition of coarse-grained sandy debris on fine-grained sediments. Some of these structures can be classified as seismites, providing evidence of intraplate seismicity within the inner part of the South American Platform during the Late Cretaceous. This seismic activity is likely related to the uplift of the Alto Paranaíba High along reactivations of regional structures inherited from Proterozoic crustal discontinuities and coeval explosive magmatism of the Minas-Goiás Alkaline Province.

Soft‐sediment deformation (SSD) structures are the syn‐sedimentary structures that can form by seismic as well as non‐seismic processes. The SSD structures commonly occur in the Semri Group of the Vindhyan Supergroup in the Kajrahat Limestone, Chopan Porcellanite and Rohtas Limestone formations, and the Glauconitic Sandstone Member. The SSD structures include, slump folds, kink bands, chevron folds, convolute beddings, contorted cross‐beds, flame structures, pinch‐and‐swell structures, breccias, sagging structures, water‐escape structures, and dykes of varying dimensions. The lagoonal and tidal depositional environments of the Kajarahat Limestone Formation (not the continental slope environment) lead to suggest that the SSD structures formed as a result of the seismic activities in them. The SSD structures of the Chopan Porcellanite Formation associated with rhyolite might have originated as a result of volcanic activities or seismicity, while those occurring in the Glauconitic Sandstone Member (Kheinjua Formation) adjacent to the Son Lineament might have formed as a tectonics‐related seismicity. The convolute bedding with large lateral extent in the Rohtas Limestone Formation looks related to seismicity in the light of its deposition along the shelf. Thus, the upper Palaeo‐Mesoproterozoic Semri Group, Vindhyan Supergroup represents varieties of the SSD structures formed mostly by seismic processes. These imply that the Central India was unstable and was a place for tectonically controlled seismic events during the upper Palaeo‐Mesoproterozoic (1,700–1,600 Ma). [ABSTRACT FROM AUTHOR]

An earthquake of magnitude M5.7 occurred in Yamutu village, Songyuan City, Jilin Province, NE China (45°16′12″N/124°42′35″E) on May 28, 2018, with a focal depth of 13 km. The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault, Second Songhua River Fault and Fuyu North Fault which lies northwest of Tancheng-Lujiang Fault (Tan-Lu Fault). The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter, caused serious disasters to the local surroundings. The visible liquefied structures include sand volcanoes, liquefied sand mounds, sand dikes and sand sills. Sand volcanoes can be divided into sand volcano with a crater, sand volcano without a crater and water volcano (no sand). Other soft-sediment deformation structures (SSDS) induced by the earthquake include deformation lamination, load and flame structures, deformation folds, dish structures, convolute bedding and water-escape structures. The formation process of the sand volcanoes comprises three stages: (1) building up excess pore-fluid pressure in the liquefied layer, (2) cracking of the low-permeable overlying layer, and (3) mixture of sand-water venting out of the ground surface. During the upward movement, the liquefied sand is injected into the low-permeable layer to form sand veins, sand sills and various types of deformation structures. Vertical distribution of seismic liquefaction structure can be divided into four zones: the thoroughly liquefied zone, the lower liquefied zone with SSDS, the upper liquefied zone with SSDS, and the ground surface liquefied zone. The liquefaction occurred at a burial depth of 2–5 m, and the thickness of liquefied sand is 2 m. NE-SW (35°–215°) trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault (Fuyu/Songyuan-Zhaodong Fault) to reactivate. The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disaster-prone areas. Meanwhile it provides abundant basic material for studying earthquake-induced SSDS in both ancient and modern sediments. The research is obviously of great significance to reveal that the northern Tan-Lu Fault has entered a stage of active seismic activity since the twenty-first century. [ABSTRACT FROM AUTHOR]

The Permo-carboniferous glacio-marine Talchir Formation of Dudhi Nala, West Bokaro Coal Basin, India, hosts soft-sediment deformation structures that originated from liquefaction and concomitant fluidization of unconsolidated sediments at or close to the sediment–water interface. Since liquefaction of water saturated sediments may be initiated by different endogenic or exogenic triggering agents, identification of the trigger needs careful analysis of the deformation structure, as well as depositional mechanism and environment of deposition of the host sediments. In-depth analysis of the studied liquefaction- and fluidization-induced soft-sediment deformation structures and sedimentary attributes of the host sediments of the studied succession unequivocally stand against the role of strong wave and tidal action, rapid sediment loading, mass-flow and subaqueous slides related shear stress, and water or gas seepage as the triggering agent. However, development of the soft-sediment deformation structures, close to sediment–water interface, closeness to syn-sedimentary fault, flowage along the tilt towards the fault, confinement within undeformed beds, episodic character and close similarities with structures that are formed during recent earthquakes, are consistent with seismic triggering for liquefaction. The studied shallow marine sediments record a sequel of climatic amelioration, glacial retreat, shallow marine sedimentation, glacio-isostatic rebound and related syn-sedimentary faulting and development of soft-sediment deformation structures. [ABSTRACT FROM AUTHOR]

With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at Dogai Coring, northern Qiangtang Basin, Tibetan Plateau. Deformation is present in the form of plastic structures (diapirs, folds and clastic dykes), brittle structures (micro–faults) and cryogenic wedges. These soft–sediment deformation features (except the micro–faults) are mainly characterized by meter–scale, non–interlayered, low–speed and low–pressure displacements within soft sediments, most commonly in the form of plastic deformation. Taking into account the geographic setting, lithology and deformation features, we interpret these soft–sediment deformation features as the products of freeze/thaw cycles, rather than of earthquake–induced shock waves, thus reflecting regional temperature changes and fluctuations of hydrothermal conditions in the uppermost sediments. The micro–faults (close to linear hot springs) are ascribed to regional fault activity; however, we were unable to identify the nature of the micro–faults, perhaps due to disturbance by subsequent freeze/thaw cycles. This study may serve as a guide to recognizing the differences between deformation structures attributed to freeze/thaw cycles and seismic processes. [ABSTRACT FROM AUTHOR]

The Kırkgeçit Formation (middle Eocene-Oligocene) is exposed in an approximately E-W direction around the city of Elazığ, eastern Turkey. This unit represents marly and sandy deep-marine sediments deposited in a slope setting with channels and contain soft-sediment deformation structures (SSDSs). These SSDSs include slump folds, chaotic strata, load casts, flame structures, convolute laminations, clastic dykes, water-escape structures and syn-sedimentary faults. The main underlying deformation processes are liquefaction, fluidization and gravity-induced loading. Some of the SSDS could be interpreted as seismites, which originated due to earthquakes that also triggered high-density mass flows. This interpretation is consistent with the active tectonics in the Elazig back-arc basin. The SSDS in the study area are compared with SSDS in other regions, as well as with SSDS in other marine deposits. In this way, findings obtained from the study area are compared with SSDS at different locations in the marine Kırkgeçit Formation around Elazığ and with similar structures developed in marine settings worldwide, such as SE Crete and NW Africa. [ABSTRACT FROM AUTHOR]

The Gyeokpori Formation in the Buan volcanic area primarily contains siliciclastic rocks interbedded with volcanoclastics. These sediments are characterized by a variety of soft-sediment deformation structures (SSDS). The SSDS in the Gyeokpori Formation are embedded in poorly sorted conglomerates; slump folds are also present in the formation. The deformation mechanisms and triggers causing the deformation are not yet clear. In the present study, the trigger of the SSDS in the Gyeokpori Formation was investigated using facies analysis. This included evaluation of the reworking process of both cohesive and non-cohesive sediments. The analysis indicates that the SSDS are directly or indirectly associated with the alternation of conglomerates and mud layers with clasts. These layers underwent non-cohesive and cohesive deformation, respectively, which promoted SSDS formation. The slump folds were controlled by the extent of cohesive and non-cohesive deformation experienced by the sediment layers in the slope environment. The SSDS deformation style and morphology differ, particularly in the case of reworking by slump activity. This study contributes to the understanding of lacustrine slope-related soft-sediment deformation structures.

A spectacularly exposed slump is described from a 120-m-long road cut between the villages of Kanod and Deva in the northeastern Jaisalmer Basin of Rajasthan, India. The Upper Jurassic part of the sediments at the outcrop was formed in a near-shore setting and belongs to the Ludharwa Member of the Baisakhi Formation. The 3-m-thick unit shows a number of asymmetric folds and thrust faults leading to an imbrication of partly lithified sandstone beds. The deformation structures allow the reconstruction of a movement towards the northwest. This agrees well with the basin configuration that shows a deepening into this direction. Although the determination of a specific trigger mechanism is difficult for soft-sediment deformation structures, an earthquake caused by synsedimentary tectonics in the basin seems to be the most likely explanation.

The article presents new data on sedimentological structures, which have been discovered at the Ryadino archaeo­logical excavation in the northeast of the Kaliningrad District of Russia (the Šešupė River Valley). Tongue-shaped and dome-shaped diapir-like structures indicate liquefaction-induced features. As the most plausible reason, the earthquake-induced shaking is discussed. A preliminary estimation of the time interval for the seismic event covers the period from the early up to the late Holocene. The reasons for seismic activity in this region can be related to neotectonic movements (including glacio-isostatic rebound) as recorded in the southeastern Baltic Sea area of the Fennoscandian ice sheet margin zone. The relation between a palaeoseismic event and the essential changes in the hydrographic network in the region is also discussed.

The study on soft-sediment deformation structures (SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years, and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers. However, few studies were conducted on the SSDS in fan delta system in the Qingshan Group, Lingshan Island. This study analyzes the classification and characteristics of SSDS especially their lithofacies association and lithologic characteristics through field outcrops investigation and thin section analysis as well. A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions, where the water became gradually shallower. The SSDS types in the Qingshan Group includes load and flame structure, ball and pillow structure, water-escape structure, hydroplastic deformation structure, plastic sandstone breccia structure, volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types: (1) seismic waves, (2) gravity and inertia effect of pyroclastic flows, (3) instant differential air pressure; which is different from slumping and tectonic earthquakes occurred in the Laiyang Group. In addition, with the lithofacies association analysis between pyroclastic flow and SSDS beds, a distribution model of SSDS related to volcanic earthquakes can be established: SSDS types changed gradually with their distance further away from the volcanic activity core. Brittle deformation which was common in the proximal zone disappeared gradually; liquefied and plastic SSDS continued to dominate in the medial zone; and slightly liquefied SSDS were developed in the distal zone. Meanwhile, the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.

The Bakken Formation (uppermost Devonian-Lower Carboniferous) in North Dakota consists of black shales with a middle member composed of mixed siliciclastics and carbonates. Millimeter to decimeter-scale soft-sediment deformation structures (SSDS) are common in the upper third to quarter of the middle member, having been observed in sixty-three out of ninety cores studied. The nine categories identified herein reflect brittle and ductile deformation and loss of sediment shear in compressional and extensional settings. They are interpreted to form due to seismically-induced folding, liquefaction and fluidization of unconsolidated sediment, as well as microfaulting and brecciation of consolidated sediment, and reflect synsedimentary tectonic movements, e.g. along faults that were active during deposition. The distribution of SSDS follows the orientation of the major structural elements rooted in the basement of the Williston Basin. The stratigraphic and spatial distribution of SSDS suggests variable tectonic activity: cores near the most active fault systems have the highest net thickness of units with SSDS, whereas those farther from the most active faults exhibit only a few deformed units. The predominance of SSDS in the upper portion of the middle member suggests there was a change from relative tectonic quiescence to a more active regime which in turn led to modifications of basin geometry and new accommodation patterns. Synsedimentary deformation might have had a positive effect on reservoir quality in deformed units by increasing porosity and permeability as a result of cohesion loss and rearrangement of grains. Additionally, multiple injection structures and complexes of small-scale normal and reverse faults could contribute to better connectivity of reservoir units. • Abundant soft-sediment deformation structures in the middle Bakken member. • Soft-sediment deformation structures record syndepositional movement of basement structures. • Seismites can serve a tool to recognize paleotectonic activity in intracratonic basins. [ABSTRACT FROM AUTHOR]

Soft-sediment deformation structures of different types and sizes are frequently observed in the lacustrine deposits of Lake Van. According to sedimentary features and regional factors, these structures are categorized as non-seismic originated and seismically-induced, soft-sediment deformation structures. Well-preserved non-seismic originated, soft-sediment deformation structures were observed in fine-grained sandy and silty deposits at three locations (Çatakdibi, Yumrutepe, and Yukarıışıklı), and occur at different stratigraphic horizons, exhibiting morphological variability as they consist of load, flame, and slump structures. The formation mechanisms of these structures are determined by the characteristics of their sedimentary facies and environmental conditions. Overloading, caused by rapid coarse sediment deposition or underwater landslides, and storm waves are identified as triggering mechanisms, while rapid sediment accumulation and underwater mass movements caused by volcanogenic shakes are the conditions responsible for the formation of non-seismic soft-sediment deformation structures, in terms of regional geodynamics. [ABSTRACT FROM AUTHOR]

An extraordinary variation of plastic and brittle deformation structures with periglacial, glaciotectonic and seismic features was observed within the unconsolidated, upper Pleistocene meandering river succession in the Slinkis outcrop in central Lithuania. Among these deformations, the following structures were described: (1) ice-wedge casts in the lower part of the sedimentary succession, linked to periglacial processes, (2) soft-sediment deformation structures, such as load structures (load casts, pseudonodules), flame structures and water/sediment-escape structures, all trapped in clearly defined layers in the upper part of the sedimentary succession, which are related to the propagation of seismic waves, and (3) faults occurring throughout the sedimentary succession, which are associated with glaciotectonic processes. To our knowledge, this is the first description and analysis of the combined presence of such a diverse range of deformation features caused by three trigger mechanisms in a meandering fluvial sedimentary succession. [ABSTRACT FROM AUTHOR]

Investigations at a construction site in Hamburg (NW Germany) exposed palaeoseismic structures from moderate to strong earthquakes. Based on the large size of large blowout clastic dykes being up to 2.0 m wide and 2.5 m high, as well as the occurrence of infill structures, erratics/rafts of up to 9 kg in weight, seismites s.s. and decimetre-scale folds or seismoslumps, the magnitude of the earthquakes could be in the order of up to M ≥ 6. This is significantly higher than previously assumed for prehistorical seismic events in NW Germany. The structures are assigned to earthquakes possibly related to NW–SE-oriented faults that are evident in Lidar and SAR surface interpretations. Organic material from blowout-related infill bowls, assumed to be synchronously formed collapse depressions, are analysed for 14C ages. The dates reveal ages between 31,500 and 1200 14C cal a BP, indicating five prehistoric earthquakes. Accordingly, three of these earthquakes occurred before and after the main Weichselian glaciation phase (ca. 31,350, 26,850 and 18,980 14C cal a BP), and two occurred during the Subatlantic (ca. 4900 and 1200 14C cal a BP). The Weichselian events indicate seismic activity in the ice marginal zone during or following interstadials/Dansgaard–Oeschger events, as well as suggesting that advancing ice sheets foster earthquakes. [ABSTRACT FROM AUTHOR]

Abstract This study reports on neotectonic deformation represented as faults, graben, and horst structures, which have been found in the uppermost 10 m of Quaternary sediments, consisting mainly of Saalian glaciofluvial and Weichselian periglacial material in northern Germany that is generally considered as a low-seismicity area. An area with up to 35 faults in a 60 m wide zone exhibits mainly extensional structures. Most of those are SE-NW-oriented and in some cases NE-SW. Soft sediment deformation structures include sand blows, blowout-related infill structures, and growth faults. Small-scaled, soft-sediment deformation structures are also found. Based on the large size of the sand blows and the widespread occurrence of small-scaled, soft-sediment deformation structures, the magnitude of the earthquakes is estimated in the order of M ≥ 5.5. Single faults exhibit a displacement of a few metres. Because some faults are overlain by unfaulted sandur sediments the system has been active over at least ~200 ka (Saalian). Several faults extend through the Weichselian periglacial layer to the present ground surface, proving ongoing deformation during the Weichselian Lateglacial and/or the Holocene. This major activity during the Saalian and the Weichselian points to the activation of old tectonic structures. A possible process can be the glacial loading and unloading associated with the isostatic rebound. Holocene and late Holocene seismic events are shown by the penetration of the Weichselian-Lateglacial periglacial layer by faults and sand blows as well as a possible blowout-related bowl with organic material and corresponding young 14C dates of <300 a cal 14C. The documented fault zone could possibly be attributed to an intraplate pre-Quaternary fault within the central Glückstadt Graben. Concurrent adjacent faults are assumed from the morphology. [ABSTRACT FROM AUTHOR]

Abstract Middle Pleistocene glaciolacustrine fan sediments are exposed along a cliff at the Baltic Sea coast, where plastic and brittle soft-sediment deformation structures (SSDS) commonly occur: (1) fold structures (various types of folds and flexures); (2) load structures (load casts, pseudonodules) and flame structures; (3) water-escape structures (WES); and (4) brittle deformation structures, such as faults (medium- and small-scale reverse and normal), and fragments of broken-up laminae. The origins of the SSDS can be linked to gravitational processes promoted by shear stresses in subaqueous debris flows on the glaciolacustrine fan and by the weight of overlying sediments; and/or to the glacial rebound of Earth's crust during deglaciation because in the Pleistocene the Baltic Sea and surrounding areas were covered by ice sheets many times. The question investigated here concerns recognition of the trigger mechanisms responsible for the development of SSDS, and the criteria needed to recognize those mechanisms based on the lithological and deformational features of the sediments involved. Some types of SSDS can look similar regardless of trigger mechanisms, but some occur more often as a result of a specific mechanism. Is it possible to distinguish SSDS of seismic origin in a glaciolacustrine fan succession affected by multiple debris flows and of SSDS that evolved as a consequence of slope processes? We suggest criteria to recognize SSDS triggered by the glacioisostatic rebound as well as those which can develop as a result of the rebound and slope processes. [ABSTRACT FROM AUTHOR]

It is demonstrated here for the first time how Palaeoproterozoic stromatolites survived seismic disturbance of their substrate. The stromatolites under study could have been cyanobacteria or any other photoautotrophic microbes, which formed mats that covered a substrate of very fine-grained sandstones and mudstones of the Chaibasa Fm. in eastern India. The sediments represent a shelf environment. The local abundance of the stromatolites suggests that the low-energy environment formed a suitable habitat. The common phases of tectonic quiescence were, however, occasionally interrupted by seismic shocks. These were sufficiently strong to deform the mat layers, the lower parts of which might already have been (semi-) consolidated. The mats became partly folded, partly faulted, and already consolidated parts of the stromatolite layers broke off. This can be deduced from the angular shapes of part of the broken-off fragments. It appears, however, that part of these fragments were still sufficiently soft to become rounded and deformed by rolling over the seafloor, probably under the influence of tidal currents. When come to rest, these fragments served as a new substrate for new generations of the micro-organisms. These micro-organisms thus survived by continued growth on the reworked fragments and built up new stromatolites that may show an ‘angular disconformity’ with the stromatolites of their substrate. It thus is shown that stromatolites have an adequate response to a sudden disturbance of their habitat, and that they survive earthquakes by colonization of broken-off fragments. We call the ‘healed’ fragments ‘tomboliths’ (tumbled stones).

The fine-grained autochthonous sedimentation in the deep part of a Late Triassic lake was frequently interrupted by gravity-induced mass flows. Some of these mass flows were so rich in water that they must have represented slurries. This can be deduced from the soft-sediment deformation structures that abound in cores from these lacustrine deposits which constitute the Yanchang Fm., which is present in the Ordos Basin (central China).

Abstract Soft-sediment deformation structures (SSDSs) with bedding-parallel lenticular morphology have been occasionally reported and called different names, such as loop bedding or pillow bed. However, there is no understanding of the formative conditions that give rise to them versus other SSDSs. Similar bedding-parallel, lenticular, dolomite bodies, tens of centimeters thick with quite variable lengths (30 cm–30 m), occur across a large area (>3000 km2), exclusively in the St. Louis Member (Late Vasean, Mississippian) of the Slade Formation in east-central Kentucky, USA. Field investigations indicate that the lenticular structures, along with other associated SSDSs, represent a persistent deformed horizon that is correlative with and occurs symmetrically around the more intensely deformed Big Sinking Bed, which was previously interpreted as earthquake-induced SSDSs. Based on multiple lines of evidence, the lenticular structures are interpreted to represent distal expressions of the same seismic event that generated the proximal Big Sinking Bed. The lenticular structures were subsequently dolomitized and their selective dolomitization is attributable to their brittle deformation during the earthquake, which resulted in preferentially developed fracture porosity that allowed more efficient circulation of Mg2+ fluids throughout the lenticular structures. Petrographic and stable-isotopic evidence also suggests that the selective dolomitization postdates the deformation, probably related to a brine-reflux system developed during the first marine transgression following subaerial exposure of the St. Louis carbonates. Based on comparative analysis with other global cases, the bedding-parallel, lenticular structures are interpreted to represent a distinct type of SSDS, comparable to boudinage in tectonic deformation. Their formation reflects a situation in which seismically-elevated pore-fluid pressure is lower than vertical confining stress but higher than horizontal confining stress. A prominent occurrence of lenticular-type SSDS is a potential indicator of syndepositional extensional stress regime, which is testified by tectonic settings of all known cases, including the Kentucky dolomite bodies. Highlights • Bedding-parallel Lenticular structures from St. Louis Member, Slade Formation (Eatern Kentucky) are seismites. • Later selective dolomitization of lenticular structures due to earthquake-induced fracture porosity • Bedding-parallel Lenticular soft-sediment deformation structures indicate syndepositional extensional settings. • Useful indicators for rheological behaviors and fluid-pressure evolution during soft-sediment deformation. [ABSTRACT FROM AUTHOR]

Abstract Integration of the sedimentological and ichnological characteristics of the Campanian-Maastrichtian succession of the Nkporo Formation, Afikpo Sub-basin, particularly in the Itigidi-Ediba area reveals a prograding deposit that is considered to record a river-dominated, wave-influenced and tide affected (Rw t ) delta. Facies analysis of the succession indicates six facies associations (FA 1 to 6) suggesting deposition in the shelf, prodelta, distal delta front, proximal delta front, distributary mouth bar and bay-fill sub-environments. These deposits are characterized by abundant carbonaceous detritus; current-, storm-, wave-, and tide-generated sedimentary structures; low to moderate diversity, sporadically distributed trace fossil assemblages dominated by depauperate Cruziana and Skolithos ichnofacies that suggest relatively stressed environmental conditions; coarsening upward of most individual facies and the overall succession, and the presence of soft-sediment deformation structures. Zoophycus ichnofacies occurs as opportunistic burrows in fully marine deposits. The frequent occurrence of Diplocraterion sp. indicates a high rate of sedimentation. These ichnofossils are dominantly dwelling and feeding structures with limited grazing behaviour constructed by suspension and deposit feeders. Highlights • Detailed sedimentary facies and ichnology of deltaic deposit discussed. • Hydrodynamic and coastal processes that prevailed during the Campanian-Maastrichtian periods highlighted. • Reconstruction of the depositional environment and the distribution of trace fossil suites in the deltaic deposit. • Environmental significance of the encountered trace fossil assemblages. [ABSTRACT FROM AUTHOR]