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A suite of soft-sediment deformation structures occurs within the basal sands and gravels in the non-marine Pleistocene succession in the Noarlunga Embayment of the Cenozoic St Vincent Basin south of Adelaide, South Australia, the significance of which has hitherto gone unrecognised. The inclusion of large, isolated blocks of well-bedded sands randomly encased within fluidised, structureless clayey sands indicates that the soft-sediment deformation was intense, occurring soon after deposition by liquefaction of a still saturated sediment. Seismic activity has been, and continues to be, a regular occurrence along the adjacent Adelaide fold belt. The intensity of the deformation is comparable to the thixotropic response to earthquake activity observed during the Christchurch (New Zealand) earthquakes of 2010 and 2011, the earthquakes and aftershocks near Quorn, South Australia, in January 1887, in the southeast of South Australia in May 1899, and west of Adelaide in April 1954. This, however, is the first record of an interpreted seismite in the St Vincent Basin, although its full extent is yet to be mapped. [ABSTRACT FROM AUTHOR]

Through core observation, thin section identification, and logging and testing data analysis, the types and characteristics of event deposits in the ninth member of Yanchang Formation of Triassic (Chang 9 Member) in southwestern Ordos Basin, China, are examined. There are 4 types and 9 subtypes of event deposits, i.e. earthquake, gravity flow, volcanic and anoxic deposits, in the Chang 9 Member in the study area. Based on the analysis of the characteristics and distribution of such events deposits, it is proposed that the event deposits are generally symbiotic or associated, with intrinsic genetic relations and distribution laws. Five kinds of sedimentary microfacies with relatively developed event deposits are identified, and the genetic model of event deposits is discussed. Seismites are mainly developed in the lake transgression stage when the basin expands episodically, and commonly affected by liquefaction flow, gravity action and brittle shear deformation. Gravity flow, mainly distributed in the high water level period, sandwiched in the fine-grained sediments of prodelta or semi-deep lake, or creates banded or lobate slump turbidite fan. It is relatively developed above the seismites strata. The volcanic event deposits are only seen in the lower part of the Chang 9 Member, showing abrupt contact at the top and bottom, which reflects the volcanic activity at the same time. Anoxic deposits are mostly formed in the late stage of lake transgression to the highstand stage. Very thick organic-rich shales are developed in the highstand stage of Chang 9 Member, and the event deposits in the depositional period of these shales are conducive to potential reservoirs.

The Sawtooth Fault in central Idaho, USA, is a range‐bounding normal fault with a Late Pleistocene–Holocene scarp near the up‐valley ends of several range‐front lakes. Cores from Redfish Lake, which spans the fault, exhibit evidence of catastrophic sediment re‐mobilization in two sequences consisting variably of intraclastic mud‐clast conglomerate, massive homogenite, and graded silt and clay. Event strata of the younger sequence are in unconformable contact with Pleistocene sediments in two cores on the northern lake‐basin slope, suggesting transport from the down‐valley portion of the lake toward the basin center. A silt cap associated with the event strata is preserved at all coring sites. The event sequence, distributed lake‐wide, dates to ca. 4300 cal a bp, while additional event strata in two Redfish Lake cores pre‐date the 7627 cal a bp Mazama ash. We propose seismic triggering of the sediment disruptions. Asynchronous event stratigraphy in Pettit Lake, 15 km south of Redfish Lake, suggests distinct ruptures along two portions of the Sawtooth Fault. The sedimentology and geochemistry of remobilized sediments in both lakes indicates that sources included Late Pleistocene and early Holocene lake‐floor sediments and suggests failures that cut deeply into the sedimentary sequence. Cores collected from Stanley Lake (17 km northwest of Redfish Lake) following the nearby 2020 M6.5 Stanley earthquake exhibit a thin, sandy event horizon associated with documented delta collapse. Subaerial slope failures associated with the 2020 event left no widespread disturbance stratigraphy in Redfish Lake. We conclude that the large‐magnitude lake‐floor sediment remobilization events probably required rupture of fault sections proximal to Redfish and Pettit lakes. [ABSTRACT FROM AUTHOR]

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. [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.

Large quantities of Cretaceous Fe-oxidising bacteria (FeOB) are documented here for the first time in carbonate injection dykes. These injection dykes occur in fissures of a Palaeozoic metamorphic complex in the Geresd Hills, Hungary, and are made up of microlaminated haematitic carbonate that contain very well preserved helical FeOB stalk fossils similar to recent iron-oxidising Gallionella and Mariprofundus. The presence of filament clusters with semi-parallel textures suggests aerotactic bacterial cell movements. Fractal analysis of the filament clusters showed higher fractal dimension values (D f ∼ 1.9) compared to the typical fractal dimension values of the texturally similar, but inorganic Diffusion-Limited Aggregation (DLA) structures (D f ∼ 1.7). This finding is interpreted to suggest that the observed filamentous texture is of microbial origin. Cretaceous basaltic intrusions that penetrated the gold-bearing pyritic metamorphic basement launched a low-temperature flow of reductive iron-rich fluids. Well‑oxygenated bottom waters percolated through thin pelagic sediments and picked up ferrous iron from the pyritic metamorphic bedrock and made it available for the Fe-oxidising microbes. Reactivation of a major fault zone (Mecsekalja Zone) resulted in the development of extensional faults in the metamorphic basement beneath the seafloor. Pelagic carbonate sediments with FeOB mats were drawn into these fissures, forming a network of injection dykes. This study shows that fractal dimension analysis and directional analysis may be a helpful method to differentiate FeOB textures from inorganic textures in ancient rocks. The presented results are expected to provide useful analogues to aid the reconstruction of similar palaeoenvironments worldwide. • First globally: Cretaceous iron bacteria in injection dykes. • FeOB's stalks suggest aerotactic motion. • Fractal dimensions distinguish FeOB from inorganic structures. • Submarine pyritic rocks served as electron donors for Fe-bacteria. • Pelagic sediment drawn into seismic shock induced fractures to form injection dykes. [ABSTRACT FROM AUTHOR]

Sedimentary investigations, petrography, heavy mineral and conglomerate component analyses, and detrital zircon U-Pb geochronology were conducted to reconstruct the sedimentary and source-to-sink evolution of the Southern Junggar Basin, an intracontinental basin in the late Mesozoic. A paludal deltaic environment evolved into a fluvial environment, and abruptly prograded into alluvial fan and aeolian environments in the Late Jurassic, which was replaced by fan deltaic and lacustrine environments in the Early Cretaceous. Three source-to-sink systems were identified, according to different source-to-sink system features. In the northern piedmont of the Tianshan Orogenic Belt, the North Tianshan Orogenic Belt mainly provided sediments in the Late Jurassic. The North Tianshan and Central Tianshan Orogenic Belt both supplied sediments in the Early Cretaceous. In the northern piedmont of the Bogda Orogenic Belt, the Bogda Orogenic Belt was constantly the primary provenance, and the Tianshan Orogenic Belt also provided sediments. Sediment recycling occurred in the basin margin in the Late Jurassic and more metamorphic rocks were denudated in the Early Cretaceous. The source-to-sink system shrank in the Late Jurassic and expanded in the Early Cretaceous. This source-to-sink evolution and the conglomerates in the Kalazha Formation with seismite structures responded to the aridification in the Late Jurassic, the uplift of the Bogda and Tianshan Orogenic Belts in the Late Jurassic, and the exhumation of the Bogda and Tianshan Orogenic Belts in the Early Cretaceous.

In the Late Triassic the landscape NE of present-day Bristol, SW England was dominated by Carboniferous Limestone ridges and cuestas that became progressively buried by continental Mercia Mudstones and finally inundated during the Rhaetian marine transgression. Mussini et al. (2020) adopt the assertions of earlier collaborators back to Whiteside and Marshall (2008) that terrestrial vertebrate assemblages from sediments contained within karstic fissure systems in the former limestone ridges at Cromhall, Tytherington and elsewhere are restricted to the Rhaetian. We review and reject the sedimentological, stratigraphic, geomorphological and topographic arguments for this and reassert a long pre-Rhaetian (Norian) history for the vertebrate-bearing fissure systems at both Tytherington and Cromhall. We also reject the contemporaneous Rhaetian freshwater-seawater mixing zone dissolution model for the fissure systems adopted by Mussini et al. (2020) and reaffirm that the Tytherington and Cromhall fissures developed as conduit caves with a long Triassic history. Applying a new regional study of the Rhaetian transgressive surface, we also show that whilst the fissures at Cromhall remained sealed after the Norian, those at nearby Tytherington were re-exposed in the Late Rhaetian. Already partially filled with Norian sediments, the Tytherington fissures were subject to reworking on the seabed. Internal collapses, probably triggered by well documented repeated regional seismicity, led to the chaotic state of the Tytherington fills when downward moving Rhaetian marine components came to lie amongst and mix with earlier Norian terrestrial sediments. The vertebrate associations in the Tytherington fissures therefore contain a substantial Rhaetian input whilst those at Cromhall do not. [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]

The southern part of the Eastern Anatolian Plateau is a key region for understanding the tectonic activity and related deformation patterns of the Arabian–Eurasian collision zone. The geological record of seismic events collected from lacustrine deposits of Lake Van Basin is a critical requirement for seismic hazard assessment and seismic risk reduction. Our paleoseismic investigations revealed well-preserved seismites at five locations in late Pleistocene lacustrine deposits. The seismites were dated using an optically stimulated luminescence dating method and were arranged according to their ages. Their type, such as convolute, dish-and-pillar, flame, and ball-and-pillow structures, as well as their locations, ages, and stratigraphic distribution enable us to identify the responsible fault and the earthquake recurrence interval. On the basis of these properties, the Erciş Fault has been recognized as the structure responsible for creating the seismites. The time span between the seismites indicates an apparent earthquake recurrence interval of 125–250 years for large earthquakes (M ≥ 5) related to the Erciş Fault. The method applied here enriches our knowledge on the seismic hazards present in the northern Lake Van region. • Quaternary lacustrine deposits of the Lake Van Basin contain different types of seismites. • Seismites include convolute, dish-and-pillar, flame, and ball-and-pillow structures. • Seismites were formed by dextral strike-slip the Erciş Fault. • Earthquake-recurrence period for the Erciş Fault is determined as 125–250 years with OSL-dating of seismites. [ABSTRACT FROM AUTHOR]

Earthquakes and resulting tsunamis are important geological phenomena, however their sedimentary paleorecord is difficult to identify because some fabrics can be generated by other processes and the criteria for discrimination of seismic and non-seismic triggers are not fully established. This paper presents several deformation and sedimentary structures in the Middle Triassic carbonates of Upper Silesia and discusses their seismogenic and tsunami origin and controls on the deformation type, intensity, preservation potential, and geographic distribution. The deformation type and intensity were controlled by the primary lithology, whereas the lateral continuity of deformed horizons depended on the lateral extent of hosted facies. The thickness and abundance of these structures increase towards the Kraków-Lubliniec Fault Zone which bounded the area from the east and is considered as the main epicentrum of earthquakes and tsunami initiation. The discussed fabrics have a universal significance and can potentially be found in other shallow-marine carbonate successions. • The intensity and type of deformation depended on the primary lithology. • The lateral continuity of deformed horizons depended on the lateral extent of hosted facies. • The abundance and thickness of structures increase towards the reactivated fault-zone. [ABSTRACT FROM AUTHOR]

The distribution and timing of the deformation for the North Patagonian broken foreland is nowadays suggested by expansion and retraction of the orogenic activity during the middle to late Miocene Andean contractional phase. Dissimilar interpretations with diachronic tectonic schemes were proposed. Based on a new U-Pb (LA-MC-ICP-MS) zircon age of 10.6 ± 0.2 Ma and a structural analysis improved with soft sediment deformation evidences interpreted as seismites, the structural evolution and deformational events of one of the main Neogene depocenters from the North Patagonian foreland (i.e. Collón Cura basin) was developed. The structural evolution of the Collón Cura basin took place through three deformational stages during a lapse of ∼11 Myr. This involves the main structural configuration of the basin at the early-middle Miocene (∼16 Ma – 14.4 Ma), which follows up to middle Miocene (10.6 Ma), and minor evidences of deformation to the late Miocene (Pre-4.8 Ma). During the first deformational stage (∼16 Ma - 14.4 Ma), the west and east main margin fault systems of the basin were active. This stage involved the uplifting of the North Patagonian Andes and the Sañicó Massif. The deformation proceeds in the western fault system synchronously to the inactivation of the eastern fault system during the second deformational stage (14.4 Ma - 10.6 Ma). The third deformational stage (Pre-4.8 Ma) only occurred at the interior of the basin as results of in-sequence and out of sequence progression of the deformation from the main margins of the basin towards the interior of it. This stage occurred without changes in the basin configurations. The results obtained in this work indicate that the main structural configuration of the Patagonian Broken Foreland occurred since the beginning of the early-middle Miocene Andean contractional episode. In turn, the structural evolution suggests that the deformation occurred synchronously in the North Patagonian Andes as well as in the North Patagonian foreland region. [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]

The Yishu Fault Zone runs through the centre of Shandong Province (E China); it is a deep-seated large fault system that still is active. Two volcanic faulted basins (the Shanwang and Linqu Basins) in the Linqu area, west of the fault zone, are exposed to rifting, which process is accompanied by a series of tectonic and volcanic earthquakes with a magnitude of 5-8. Lacustrine sediments in the basins were affected by these earthquakes so that seismites with a variety of soft-sediment deformation structures originated. The seismites form part of the Shanwang Formation of the Linqu Group. Semi-consolidated fluvial conglomerates became deformed in a brittle way; these seismites are present at the base of the Yaoshan Formation. Intense earthquakes triggered by volcanic activity left their traces in the form of seismic volcanic rocks associated with liquefied-sand veins in the basalt/sand intercalations at the base of the Yaoshan Formation. These palaeo-earthquake records are dated around 14-10 Ma; they are responses to the intense tectonic extension and the basin rifting in this area and even the activity of the Yishu Fault Zone in the Himalayan tectonic cycle.

A 1-million m3 breccia near Laiyuan (Hebei Province, E China) occurs as a block-like lithological unit between dolo-stones of the 1.55-1.45 Ga (Early Mesoproterozoic) Wumishan Formation. It has previously been interpreted as a seismite, but it appears not to fulfil any of the commonly accepted criteria that jointly are considered diagnostic for seis-mites. Its presence in a graben-like structure with almost vertical bounding fault planes rather indicates an origin as a (submarine) valley fill. As the valley originated by tectonic activity in the form of faulting, the breccia can be considered as a secondary effect of seismic activity, but it does not represent a seismite.

Definitive criteria for identifying the triggers of soft-sediment deformation structures (SSDSs) from sedimentary deposits are still under construction. In this work, we aimed to contribute to advancing this issue describing the sedimentological characteristics of an interval of SSDSs formed in a region of the Amazonian lowlands having numerous morphostructural evidences of neotectonic reactivation. The deformed interval is 1.5 m thick and consists of load and flame structures interbedded with massive beds sandwiched between well-stratified deposits of a fluvial sandy channel succession with a radiocarbon age of 1301–1382 cal yr BP. The SSDSs are intercepted by numerous small-scale, normal graded-faults. The most interesting is that these faults display segmented, NW-SE trending planes that propagate upward after horizontal displacements of a few millimeters. Processes intrinsic to channel dynamics could not justify this fault morphology, which is related to recurrent short-lived seismic perturbations with intervening sedimentation following a main tremor. A relation to fault reactivation is proposed with basis on the fault trend compatible with the regional structural pattern and the numerous morphostructural anomalies verified in the study area, including: trellis and sub-trellis drainage; rectangular and, to a less extent, annular channels; anomalously enlarged channels; orthogonal channels and valleys; channel captures; sudden changes in channel morphology; moderate to high basin asymmetry factor (AF between 10 and 27); moderate to high transverse topography symmetry factor ( T = 0.3–0.5); and anomalous longitudinal river profiles, with concavity values (11 to 30%) indicative of rivers in process of adjustments. The morphology of the fault-graded beds described herein might constitute a feature of relevance for identifying seismites in other fluvial deposits. [ABSTRACT FROM AUTHOR]

The Gruene and Verde mud diapirs, which range in size from 70 to 95 m in diameter, are exposed within the Wilkins Peak Member of the Eocene Green River Formation near Flaming Gorge Reservoir, southwest Wyoming. These diapirs are sourced from the lower unit of the Wilkins Peak Member (lower, middle, and upper units can be defined based on dominant lithology), and were emplaced into the upper unit of the Wilkins Peak Member, cross-cutting hundreds of meters of strata. The structures contain brecciated dolomicritic and lime mudstones with minor amounts of siliciclastic clays. Pervasive quartz veining is present throughout both diapirs. Though heavily disturbed, original bedding can be seen in both localities, either dipping radially outward towards the margins of the diapir as is dominant at the Gruene diapir or tilted but near horizontal as is the dominant expression at the smaller Verde diapir. The Gruene diapir can be seen in contact with several fluvial sandstone bodies within the upper Wilkins Peak strata in outcrop, and these fluvial sandstones transition from regional, near-horizontal dips to steeply dipping beds and bedsets within 50 m of the diapir. These sands show no signs of brittle deformation, and dip ranges from 20 to 50° radially away from the center of the diapir to the north, west, and east where sands are observed. These are interpreted here to have been deformed pre-lithification, at or near the surface, by the rising mud diapir, offering an important control on the timing of diapirism near the end of the early Eocene. Deformation structures such as clastic dikes, brecciation, and convoluted bedding have been documented by others at or near this stratigraphic interval in Utah, Wyoming, and Colorado, and these smaller structures have been interpreted as seismites. We suggest that these mud diapirs are a larger-scale expression of this same seismic activity. [ABSTRACT FROM AUTHOR]

Large-scale soft-sediment deformation structures occur within fluvial sandstone bodies of the Upper Cretaceous Wahweap Formation in the Kaiparowits basin, southern Utah, USA. These structures represent an exceptional example of metre-scale fault-proximal, seismogenic load structures in nearly homogenous sandstones. The load structures consist of two types: large-scale load casts and wedge-shaped load structures. Large-scale load casts penetrate up to 4·5 m into the underlying sandstone bed. Wedge-shaped load structures include metre-scale, parallel, sub-vertical features and decimetre-scale features along the periphery of the large-scale load casts or other wedge-shaped load structures. Wedge-shaped load structures contain well-developed, medial cataclastic shear deformation bands. All load structures contain pervasive well-defined millimetre-thick to centimetre-thick internal laminae, oriented parallel to the outside form of the load structures and asymptotic to deformation bands. Both types of load structures formed because of an inverted density profile, earthquake-triggered liquefaction and growth of irregularities (a Rayleigh-Taylor instability) on the sandstone-sandstone erosional contact. The internal laminae and deformation bands formed during deformation and clearly demonstrate polyphase deformation, recording a transition from liquefied to hydroplastic to brittle modes of deformation. Decimetre-scale wedge-shaped load structures on the edge of the large-scale load casts probably formed towards the end of a seismic event after the sediment dewatered and increased the frictional contact of grains enough to impart strength to the sands. Metre-scale wedge-shaped load structures were created as the tips of downward foundering sediments were driven into fractures, which widened incrementally with seismic pulsation. With each widening of the fracture, gravity and a suction effect would draw additional sediment into the fracture. Superimposed laminae indicate a secondary syndeformational origin for internal laminae, probably by flow-generated shearing and vibrofluidization mechanisms. Large-scale and wedge-shaped load structures, polyphase deformation and secondary laminae may characterize soft-sediment deformation in certain fault-proximal settings. [ABSTRACT FROM AUTHOR]

The Concud Fault is located at the junction between the Jiloca and Teruel grabens (central-eastern Iberian Chain, Spain). The Late Pleistocene activity of this fault has been well logged from structural and palaeoseismological trench studies, but only scattered data of the Late Pliocene seismic activity exist. The Late Pliocene–Early Pleistocene syn-tectonic infill consists of an endorheic continental succession in which a 75 m-long continuous well was drilled near the Concud Fault. Along the entire well core, several types of soft-sediment deformation structures with variable morphology, size and frequency have occurred including clastic dykes, load structures and slumps. The rigorous analysis of the deformation structures, their relationships with the involved sedimentary facies, and the discrimination of possible deformation mechanisms and trigger processes allow us to interpret part of them as seismically-induced structures. The recognition of 21 deformed beds (seismites) allow the Late Pliocene–Early Pleistocene seismic history of the Concud Fault to be reconstructed. Therefore, 21 seismic events (with M ≥ 5) and an apparent recurrence period of about 45 ka have been inferred. [ABSTRACT FROM AUTHOR]

ABSTRACT Soft-sediment deformation occurs in ancient eolian dune deposits, but understanding its extent and the conditions and forces behind the deformation often remains elusive. Here we gain insight into the aerial extent and environmental conditions related to intense soft-sediment deformation, based on an exceptional three dimensional (3D) exposure of eolian dune deposits and preserved geomorphic landscape expressions in the Jurassic Navajo Sandstone at White Pocket, Vermilion Cliffs National Monument, Arizona. Deformation features include elongate northeast trending decameter-scale mounds and raised ridges cored by deformed and upturned eolian dune sets, overlain by a massive blanket sandstone with breccia blocks. The geomorphic mounds display ~40-60 m spacing, roughly perpendicular to the southerly paleoflow dune foreset directions. The geometry of the deformation is imaged by oblique aerial photography using cameras mounted on a remote control airplane and high resolution panoramas with a robotic camera mount. We interpret the exquisitely preserved deformation features as liquefaction-induced ground failure, consistent with theoretical and laboratory studies of deformation in saturated sand. A shallow water table affected by differential dune loading facilitated lateral spreading and failure. The transition to steady-state flow liquefaction near the top of the shallow water table destroyed original sedimentary structure, creating a massive sand blanket that entrained brecciated blocks ripped up during flow. The water-pressurized, upwelled sediment created the mounds (a relief inversion). In underlying deformed dune sets, deformation was intense but sedimentary structure was not obliterated as deformation progressed from initial cyclic mobility to strain-softening, but ceased prior to steady-state flow liquefaction. The spatial extent, topographic relief, and intensity of dynamic deformation suggest an origin of strong ground motion driven by long-duration surface waves of a large earthquake (> Mw 7-8), possibly related to back arc thrusting from Jurassic subduction of the Pacific plate under North America. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Kachchh in western Indian Shield, according to the Bureau of Indian Standard (IS:1893:2002), falls in Seismic Zone V. This is intriguing considering that the region is far away from active Plate margin. Apart from the recent incidences of earthquakes, there are several pre-historic/archaeological records of earthquakes in the region. Beyond these, the geological evidence of earth-movements (causing earthquakes) is provided by the occurrence of several' active' faults, which are considered geological markers of palaeoseismicity. There are records of innumerable incidences of faulting in the region in not so distant geological past. Study of fault features especially the scarp faces marking abrupt change in physical relief proves that the different levels of topography in the entire terrain are fault-bound features. Studies also confirm that the topographic difference between the high and 'sunken' features have formed due to uplift and relative down-sagging during the geomorphotectonic evolution of the terrain. Features that make the region unique are: (i) restriction of fault-related deformation zone to a narrow strip between the southern margin of Thar Desert and the south coast line of the Kachchh Peninsula; (ii) overall sub-horizontality of bedding and other topographic and planation surfaces over the entire region; (iii) evidence of fault-controlled geomorphology indicating vertical movement along fault planes; (iv) evidence constraining the time of geomorphological evolution of the terrain only during the Late Quaternary, making it the youngest neotectonically evolved terrain in the Precambrian Indian Shield. [ABSTRACT FROM AUTHOR]

The Himalayan fold-and-thrust belt has propagated from its Tibetan hinterland to the southern foreland since ∼55 Ma. The Siwalik sediments (∼20 - 2 Ma) were deposited in the frontal Himalayan foreland basin and subsequently became part of the thrust belt since ∼ 12 Ma. Restoration of the deformed section of the Middle Siwalik sequence reveals that the sequence is ∼325 m thick. Sedimentary facies analysis of the Middle Siwalik rocks points to the deposition of the Middle Siwalik sediments in an alluvial fan setup that was affected by uplift and foreland-ward propagation of Greater and Lesser Himalayan thrusts. Soft-sediment deformation structures preserved in the Middle Siwalik sequence in the Darjiling Himalaya are interpreted to have formed by sediment liquefaction resulting from increased pore-water pressure probably due to strong seismic shaking. Soft-sediment structures such as convolute lamination, flame structures, and various kinds of deformed cross-stratification are thus recognized as palaeoseismic in origin. This is the first report of seismites from the Siwalik succession of Darjiling Himalaya which indicates just like other sectors of Siwalik foreland basin and the present-day Gangetic foreland basin that the Siwalik sediments of this sector responded to seismicity. [ABSTRACT FROM AUTHOR]

Abstract: Epicontinental seismicity is currently a subject of intense study by geologists and engineers, particularly relative to triggering mechanisms, epicentral areas, and recurrence intervals. Aside from modern seismic events, much of the evidence for previous events is in the form of soft-sediment deformation, which has often been systematically overlooked or misinterpreted. Carbonates have also been systematically ignored in most attempts to understand soft-sediment deformation. Soft-sediment deformation, however, is not a unique response to seismicity; so how do we know when seismicity is implicated or not? The concurrence of four criteria has been suggested as a way to confirm the likelihood of seismogenic origins for soft-sediment deformation: 1) presence of deformation consistent with a seismogenic origin; 2) deformation that is widespread; 3) deformation that can be temporally or stratigraphically constrained across its distribution; and 4) deformation that is zoned across its distribution, showing systematic increases in frequency, size or intensity toward a likely epicentral area. The greater the concordance of these criteria, the more likely a seismogenic origin is. In order to validate these criteria, we scrutinized two very different examples of epicontinental, carbonate, soft-sediment deformation, which had been called seismites: one from the shallow, open-marine, Upper Ordovician Lexington Limestone of central Kentucky, USA, and another from the peritidal, dolomitic, Mesoproterozoic, Wumishan Formation of northeast-central China. Concurrence of criteria for Lexington soft-sediment deformation readily supports the case for a seismogenic origin, whereas for Wumishan deformation, too few criteria were satisfied to implicate seismicity. Nonetheless, after exclusion of all other possibilities for Wumishan deformation, seismicity stood out as the only likely cause. Although concurrence of the four noted criteria in soft-sediment deformation almost certainly does indicate a seismogenic origin, the co-occurrence of criteria is rare and wholly dependent on past depositional environments and modern occurrence. Hence, the four criteria cannot be used as universal seismogenic indicators, and in the absence of such indicators, we must continue to rely upon the integration of tectonic, structural, and paleoenvironmental clues for substitute corroboration. [Copyright &y& Elsevier]

Abstract: Stratigraphic intervals characterized by varied and complex styles of soft-sediment deformation structures are well preserved in Miocene and Late Pleistocene to Holocene deposits of a sedimentary basin located in Northeastern Brazil. The Miocene strata, represented by the Barreiras Formation, record only brittle structures, including numerous faults and fractures with straight and high angle-dipping planes that are often filled with sands derived from overlying beds. Folds consisting of broad anticlines and synclines are also present in this unit. The Late Pleistocene to Holocene deposits, named Post-Barreiras Sediments, contain an indurated sandy package with a large variety of ductile and brittle deformation structures (i.e., massive sandstones with isolated sand fragments and breccias, undulatory strata, sand dykes and diapirs, sinks and bowls, pebbly pockets, plunged sediment mixtures, fitted sand masses, cone-shaped cracks, fault grading and sedimentary enclaves). These features, confined to sharp-based stratigraphic horizons that progressively grade downward into undisturbed deposits, are related to seismic shocks of high surface-wave magnitude (i.e., Ms>5 or 6). Amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic-wave propagation. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the depositional environment, producing laterally extensive seismites. The close proximity to earthquake epicenters would have promoted pervasive re-sedimentation due to pore overpressure, resulting high volumes of massive sandstones and breccia. The similarity between deposits with correlatable strata from many other areas along the Brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large (i.e., extension of several hundreds of kilometers) geographic area. Thus, the modern seismicity recorded along Northeastern Brazil was recurrent during the Quaternary and, perhaps, also in the Pliocene. The estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the Brazilian coast experienced tectonic stress through the last geological episodes of its evolution, which would have favored sediment accumulation and penecontemporaneous re-sedimentation. This geological context is unexpected in a passive margin, inducing to revisit the debate on how active is a passive margin. [Copyright &y& Elsevier]

Abstract: The detailed study of four deformed intervals from the Holocene fluvio-lacustrine deposits of the Santa Fe–Sopetrán Basin in northern Colombia shows 17 types of soft-sediment deformation (SSD) structures. Evidence indicates that seismic activity was responsible for the SSD structures, a conclusion reached after considering the environmental conditions at the time of sediment deposition and shortly after, and the detailed analysis of the driving force systems. Other triggers (i.e. overloading and rapid sedimentation), however, are not discarded. Intervals showing SSD structures occurred at centennial frequencies and apparently resulted from Mw 6–7 earthquakes. The Holocene age of these major shaking events should be seriously considered when evaluating the seismic hazard and risk for the middle Cauca Valley and the nearby city of Medellín with 3million inhabitants. [Copyright &y& Elsevier]

Abstract: Prominent barium concentration anomalies that appear within earthquake brecciated layers (seismites) in the late Pleistocene lacustrine Lisan Formation in the Dead Sea Basin (DSB) are described and discussed here for the first time. Chemical analyses of samples from vertical profiles through the seismites display asymmetric Ba concentration peaks. The peaks start a few centimeters above the seismite''s base and gradually rise to maxima reaching some 1000ppm Ba, before falling off to background values (around 100ppm), or abutting against the upper boundary of the breccia layer. High resolution SEM and electron microprobe analyses disclose that the Ba in the anomalies resides within prismatic crystallites (mostly<2µm in length) composed of a Ba(Sr)SO4 mineral (designated “BM” henceforth). These are lacking altogether in the normal (non-seismic) underlying and overlying sediments. The crystallites are much smaller than the adjacent, supporting matrix grains of the gradually-bedded seismite, and show no size-sorting relationship with the latter. The peaks of the anomalies reflect higher population density, rather than larger crystal sizes, of the BM crystallites therein. Mass balance calculations show that the mass of Ba2+ dissolved in the lake above a unit area of the seismites was mostly several times larger than that found in the seismite. The concentration of Ba2+ in DSB Ca-chloride brines is mostly lesser than that in the DSB Lake, ruling out the former as a source of Ba to the anomalies. We propose that, during earthquakes, the uppermost bottom sediment layers in the DSB Lake were shaken and re-suspended into the overlying brine. The larger, faster-settling fragments and grains remained almost intact or were rapidly removed, unaffected, from the slurry. However, the finer grains remained in suspension for longer periods, allowing nucleation and growth of BM crystallites on their surfaces from the surrounding brine before reaching the bottom. The lag of Ba trapping behind the breccia accumulation and the asymmetrical peak shapes of the anomalies are accounted for by decreasing dilution of the Ba-rich finer particles by Ba-poor coarse grains during seismite accumulation, as reflected by the graded bedding of the seismite layers. The supply rate of Ba2+ to the lake by freshwater and brines was more than sufficient to account for the buildup of Ba in recurring seismites separated by seismically quiescent intervals as short as 100yr. [Copyright &y& Elsevier]

Five successive fossil submarine slides have been mapped and described in the Sobrarbe deltaic complex (Ainsa Basin, Spanish Pyrenees). These slides affect and remove up to 15% of the delta front. The head of the scar surfaces is recognized clearly in the field due to the angular unconformity between the infilling sediments and the underlying layers. Most of the slide scarps trend 55°N with 20° to 40° dips indicating north-westward sliding. Downslope, traces of the sliding surfaces parallel stratification. However, these surfaces can be identified by displaced masses, resedimented sandstones and soft-sediment deformation features such as metre-scale half-grabens, normal faults and tension cracks; all the surfaces indicate a sliding displacement toward the north-west. A three-dimensional model built from topographic data with Earth Vision® software shows the architecture of the slide surfaces and provides an estimation of the volume of each sedimentary body within the limit of the studied area. This study also indicates that: (i) the sediments have been cut and carried away before their lithification; (ii) the sedimentation rate infilling a single slump scar is estimated to be about 8 m per 1000 years, i.e. 10 times higher than in the overall area of the Sobrarbe deltaic complex; (iii) each composite scar progressively develops and infills by retrogressive slumps; (iv) the successive slide surfaces stack vertically in a collapse complex structure and migrate downward to follow the sea-level drop between two successive collapse complex structures; (v) the development of the scars in the Sobrarbe delta is described from a seven-stage conceptual model starting with a regressive event; and (vi) the triggering of the Sobrarbe instabilities is controlled by high values of sedimentation rate, relative sea-level falls mainly controlled by tectonic uplift, and likely seismic activity. [ABSTRACT FROM AUTHOR]

Abstract: We study earthquake-induced soft-sediment deformation (seismites) in reference Quaternary sections of southeastern Altai. Sediments in the sections bear signature of liquefaction and fluidization and deformation is localized in thin (few centimeters to 0.5–1.0 m) continuously striking and frequently repeated layers sandwiched between undeformed sediments. The soft-sediment deformation records coseismic motion of different slip geometries. Seismic origin is also inferred for layers and lenses of coarse colluvium slid into the lake bottom from the slopes, which intrude plane-bedded silt and sand and vary in thickness from a few centimeters to one meter. The occurrence of seismic soft-sediment deformation at different stratigraphic levels of the Quaternary and in the Upper Pliocene Beken Formation confirms the high seismicity of southeastern Altai in Quaternary time. [Copyright &y& Elsevier]

• The Moradabad fault (MF) was mapped in the Ganga basin and the Himalaya. • Its doubted-extension into the Himalaya resolved from geomorphological and field studies. • This is neotectonically active, triggered by the Himalayan tectonics. • The geomorphic impression shows the signs of compression in the up-thrown block of the fault. • Normal faults are developed at the releasing bend. The present study focuses on the neotectonic perspective of a subsurface basement fault, i.e., the Moradabad Fault (MF) in the Ganga basin. This is a ∼163 km long NE-SW trending prominent pre-Himalayan subsurface structure that participated in many phases of tectonic movement during and after the Himalayan orogeny. At present, it is deep-buried under the alluvium, and frequent geomorphic readjustments are seen in the fluvial archives around this fault. The datasets presented here include tectono-geomorphological analysis, transverse-tectonic analysis, previous seismic records from the earthquake catalogs and the associated seismites, and the Ground Penetrating Radar (GPR) studies. The available geological maps limit the northern end of the MF at the Himalayan front, and further northward, it is marked as lineaments. However, the recent geological evidence such as the river alignment, river confluence, landslides, faceted spurs, triangular facets, truncated spurs, fault scarps, structural terraces, and the alignment of the low to moderate magnitude seismic events having parallel trends with the MF may conclude that it is not just a matter of coincidence. However, these features are likely aligned due to the post-Himalayan reactivation-regeneration of the basement structures. It is, therefore, argued that these linear structures showing active deformation are the extension of the MF into the Himalayas, and hence the lineament terminology for these structures should be abolished. The MF has a curved fault-line with the existence of the releasing bend in a transtensional regime. The up-thrown block shows the signs of compression, evidenced by the geomorphological signatures. The fault-bend is characterized by oblique deformation may be accommodated by oblique-slip faulting or dip-slip fault displacements. Tectonic geomorphological characteristics, morphostratigraphic record, GPR data, seismic events, and the basement contour model suggest the Moradabad fault is neotectonically active and is influenced by the Himalayan tectonics. [ABSTRACT FROM AUTHOR]

Abstract: South-central Chile is one of the most geodynamically active areas in the world, characterized by frequent volcanic eruptions and numerous earthquakes, which are both recorded in lake sediments. In Lago Icalma (39°S), long piston and short gravity coring, as well as 3.5 kHz high-resolution seismic profiling, have been carried out in order to study the Holocene sedimentary infill of the lake, with a special focus on earthquake-triggered deposits. Macroscopic description of sediment cores and detailed grain-size analyses allow us to identify four types of seismically-induced deposits, or “seismites”: slump deposits, chaotic deposits, turbidites s.s. and homogenites. Homogenites are characterized by the occurrence of three distinct units on grain-size profiles (i.e., a coarse base, a thick homogeneous unit topped by a thin layer of very fine sediment) and by the typical distribution of the grain-size parameters in a skewness–sorting diagram, while turbidites s.s. are characterized by a continuous fining-upward trend. Radiocarbon, 210Pb dating, and tephrochronology allow us to demonstrate that the regional seismotectonic activity was probably very high between 2200 and 3000 cal years BP as well as between 7000 and 8000 cal years BP and that none of the historically documented earthquakes has triggered a seismite in Lago Icalma. The most recent seismite recognized in the sediments of Lago Icalma is a slump deposit dated at 1100±100 AD, i.e., older than the period covered by historical records. The remarkable record of seismites between 2200 and 3000 cal years BP is probably influenced by a major eruption of Sollipulli volcano at 3000 cal years BP, which has rejuvenated the stock of terrigenous particles available for erosion, by depositing a thick layer of pumices all over the watershed of Lago Icalma and by clearing the vegetation covering the volcanic ash soils. This paper demonstrates that the record of seismically-triggered deposits in lake sediments is not only controlled by the intensity of the triggering earthquake and the occurrence of unstable sediment along the lake slopes but also by the presence of particles available for erosion/remobilisation in the watershed. [Copyright &y& Elsevier]

In the lower Dacian deposits from Valea Rea point (Prahova county, south of Câmpina) two seismites zones (sensu Seilacher, 1969) have been recognized: segmented and rubble. The first zone is marked by the existence of fragmented thin layers and laminae, as well as by collaps structures or by remains of Skolithos type cylindrical, vertical galleries. The second zone is characterized by thin and discontinuous laminae, possible of algal-mat nature. [ABSTRACT FROM AUTHOR]

Based on studies of regional tectonic setting and the observation of drilling cores, the seismite is recognized in member III at Shahejie Formation in the Xianhe area of the Dongying sag. The principal mark of the seismite is the development of all kinds of soft sedimentary deformation structures, such as micro-step fault, intraformational minor fold, deformation, vibrational liquefied sandstone dike and seismic breccias. By observing the drilling cores of He 152, Wang 59, Niu 38, Niu 22 and so on, we found that the vertical sequences of the seismite are different because of the differences in structure and seismic intensity. We also found that different seismite structures are formed by different seismic intensities and that the relationships between seismite structures and paleoearthquakes were further confirmed by studying the relationship between all kinks of seismite structures and seismic intensity. Researches on reservoirs show that seismite can be an effective reservoir. These researches provide an important geological theoretical foundation for the study of the tectonic evolution of the Dongying sag and for seismite identification and description, and also supplies evidence for the researches of paleoearthquakes. [ABSTRACT FROM AUTHOR]

The Middle Permian Wandrawandian Siltstone of the southern Sydney Basin is well exposed along the coastline from Lagoon Head in the south to North Head in the north near Ulladulla in southern New South Wales. The unit is dominated by fossiliferous siltstone and mudstone, with abundant dropstones and minor pebbly sandstone interbeds, and contains an interval of well-preserved and extensive soft-sediment deformation structures. These deformation structures occur mainly in the middle part of the cliff sections and are bounded above and below by undeformed sedimentary units of similar lithology. A wide range of soft-sediment deformation structures have been observed, including cracks, sandstone and sandy mudstone dykes, a possible sand volcano, networks of relatively small and closely connected fissure-like structures, metre-scale complex-type slump folds, flexural stratification, concave-up depressional structures, small-scale normal faults (with displacements usually <1 m), shear planes, and breccias (pseudonodules). The slumps and associated deformations are here collectively interpreted as representing a seismite deposit attributable to penecontemporaneous deformation of soft, hydroplastic sediment layers following a liquefaction triggered by seismic shocks. The timing of the inferred earthquake events appears to correspond to the onset of a major basin-wide tectonism during the Middle Permian. [ABSTRACT FROM AUTHOR]

Turnagain Arm is a semidiurnal hypertidal estuary in southeastern Alaska with a recorded tidal range of 9 m. Contorted bedding and flow rolls preserved in tidal sediments within the estuary have previously been interpreted as resulting from the Mw 9.2 Great Alaskan earthquake of 1964. Horizons of flow rolls between undeformed beds in sediments and rock strata have been used to infer ancient earthquakes in other areas. Although many types of soft-sediment deformation structures can be formed by earthquakes, observations of sedimentation on tidal flats in the inner parts of Turnagain Arm in the summers of 2003 and 2004 show that a wide range of soft-sediment deformation structures, similar to those inferred to have been formed by earthquakes, can form in macrotidal estuaries in the absence of seismic shock. During sedimentation rate measurements in 2004, soft- sediment deformation structures were recorded that formed during one day's tide, either in response to overpressurization of tidal flats during rapid tidal drawdown or by shear stress exerted on the bed by the passage of a 1.8 m tidal bore. Structures consisted of flow rolls, dish structures, flames, and small dewatering pipes in a bed 17 cm thick. In the future, if the flow rolls in Turnagain Arm were found in isolated outcrops across an area 11 km in length, in an estuary known to have been influenced by large-magnitude earthquakes, would they be interpreted as seismites? These examples show that caution is needed when using horizons of flow rolls to infer paleoseismicity in estuarine deposits because many of the mechanisms (tidal flux, tidal bores, slumping, flooding) that can cause deformation in rapidly deposited, unconsolidated silts and sands, are orders of magnitude more common than great earthquakes. [ABSTRACT FROM AUTHOR]

Abstract: The main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies. The large variety of seismites, depends on the sedimentologic, hydrodynamic and diagenetic characters of the deposits subject to seismic shocks. On a given site, generally different types of seismites cane be related to the same seismic event. These peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes. Therefore, the structures discussed must necessarily be placed in a detailed geological context. [Copyright &y& Elsevier]

Abstract: The lower part of the Cotham Member in the Penarth Group (latest Triassic, Rhaetian) of the UK incorporates a uniquely extensive metre-scale horizon of soft-sediment deformation. Interpreted as a seismite, it shows evidence for only a single seismic event even at its thickest development. It is recorded from more than forty sites across at least eight discrete sedimentary basins covering >250,000 km2, and originally must have covered a still larger area. Such a widespread horizon of soft-sediment deformation, unique for the UK Phanerozoic and implying a seismic event of exceptional magnitude, is difficult to account for by conventional terrestrial mechanisms. Contemporaneous volcanism in the Central Atlantic Magmatic Province (CAMP) was too far distant to cause the deformation, and the tectonic setting of the region was not conducive to earthquakes on this scale. Slump fold long axes suggest an epicentre broadly in the southern Irish Sea or St. George''s Channel. Impact of a km-scale asteroid here potentially could produce the observed sedimentological effects across the UK, but any late Triassic impact structure would now be concealed by a km or more of younger strata. At its thickest development, in Northern Ireland, the seismite is succeeded by a rip-up breccia and hummocky- and wave-rippled cross stratification. These facies, and their position immediately above the seismite, are consistent with the effects of a tsunami arising directly from the seismic event. Tentative evidence for a tsunamite of this age has also been reported from southern France. The putative tsunamite in Northern Ireland is succeeded by a desiccation-cracked hiatus which may correlate with a similar hiatus truncating the seismite at sites in southern England. The hiatus in southern England correlates closely with a δ 13C isotope excursion that has been traced from eastern Europe across to western North America and is associated with significant biotic changes. The ultimate cause of the seismite and associated tsunamite remains unclear. No impact crater of appropriate age or location is currently known and other evidence for impact at this time is at best equivocal. It is considered here that impact of a km-scale asteroid may have caused the observed sedimentological effects in the Lilstock Formation across the UK area, but was not necessarily a significant contributory factor in the generation of either the isotope excursion or of the biotic changes through the Triassic–Jurassic boundary interval. [Copyright &y& Elsevier]