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Soft-sediment deformation structures (SSDSs) are widely developed in the lacustrine sediments of paleo-dammed lakes in tectonically active regions and contain a wealth of information on regional fault activity. In this study, multiple SSDSs (load structures, small-scale slump structures, droplets, diapir and pillow structures, silty-clay pillars and large-scale slump structures) were identified in the strata of the Late Pleistocene lacustrine sediments in the Tashkorgan River drainage in northeastern Pamir. The deformation mechanisms of the SSDSs were related to the liquefaction, fluidization and thixotropic behaviors. The regional tectonic settings and SSDS features point toward a trigger mechanism with seismic activities and indicate that the seismogenic faults were possibly related to the southern part of the Kongur Shan extensional system. Accelerator mass spectrometry (AMS) radiocarbon dating data showed that the SSDSs in the Tashkorgan lacustrine sediments formed 30,221-29,932 cal BP and 25,825-25,317 cal BP. The results of this study improve our understanding of fault activity and geodynamic processes in northeastern Pamir during the Late Pleistocene.

Soft-sediment deformation structures were identified along Nandakini River valley near Chamoli village of Garhwal Lesser Himalaya. The deformation, in each outcrop, is restricted to a single stratigraphic layer bounded by undeformed flat-lying layers, eliminating the influence of slope failure. The structures are multiple liquefaction features like sand dikes, flame structures, pear-drop disturbance and downward warping of beds. The preferred interpretation is that the deformations resulted from earthquake-induced liquefaction and their existence adjacent to the Nandaprayag Fault can be related to episodic seismicity that occurred along this fault. However, more data and dating technique is needed to constrain the timing and distance to the causative seismic source. It is possible that more than one earthquake has effected the deformations.

Cores from the middle Eocene sediments of the Dongying Depression of the southern Bohai Bay Basin in east China yield various kinds of sedimentary deformation structures. They include microfolds, load casts, flame structures, ball-and-pillow structures, load-cast ripples, pinch-and-swell structures, boudinage structures, sand dikes, microfaults, and cataclastic breccias. Gravity flows, including turbidites and debris flows, also occur in the study area. The deformation layers can be divided into plastic deformation and brittle deformation types. These develop in a succession composed mainly of dark finely laminated and massive mudstone interbedded with thin sandstones and carbonate rocks that accumulated in a low-energy semi-deep to deep lacustrine environment in a tectonically active setting. Considering the facies attributes in the study area, intrinsically possible trigger mechanisms such as rapid sediment loading and storm currents are absent. Thus, the sedimentary deformation features should be induced by seismic activity, and the same with the gravity flows. These seismites are interpreted to have originated from earthquakes with magnitudes exceeding M 5.6. Basin-controlling faults in the north border of Dongying Depression give rise to the occurrence of seismites. The increasing occurrence frequency of seismites from Es4u to Es3l corresponds with the increase in the activity velocity of the basin-controlling faults. Compared with the seismites developed in other fault depressions in the Bohai Bay Basin, seismites developed in the Dongying Depression are relatively smaller scale and are dominated by microfault layers, relatively more cohesive sediments, and greater distance between seismites and active faults results in the occurrence of these features.

Quaternary sediments are preserved in disconnected patches along the middle and lower reaches of major river valleys like Damanganga, Par, Ratakhadi and Dongarkhadi in the Dadra and Nagar Haveli region of Konkan coastal belt, Western India. These deposits mainly consist of stratified sand, silt, clay and gravel beds. The study area has been earlier affected by moderate earthquakes. The identified soft-sediment deformation structures (SSDS) are mainly developed in the sand silt, sand gravel and clay beds; and includes intrusive sedimentary bodies (dykes and sills), slump structures, suspended clast blocks and convolute structures. The nature, shape and dimension of SSDS suggest that the trigger mechanism and driving forces for the origin of these structures were seismic shock waves. Sediment loading and storm events as a trigger for the SSDS are less likely the reason and the proximity of these structures to the faults support the inference that it may be of seismic origin. Deformation in the Quaternary sediments of Dadra and Nagar Haveli imply the presence of neotectonic activity and points to an earthquake of magnitude >5.5 that struck the study area after sediment deposition.

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.

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.

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.

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

Quantifying the magnitude of an earthquake is very important for long-term and medium-term earthquake prediction, post-earthquake emergency rescue and seismic hazard assessment. Paleoseismology is the investigation of past earthquakes in the geological record, in particular their location, timing and size. Uncertainties remain in the paleoearthquake magnitudes determined by traditional surface rupture parameters, especially because most seismic events do not result in surface ruptures. In order to address the problem of magnitude evaluation of earthquakes that did not reveal major dislocations, this paper deals with the methods used to determine the seismic shaking intensity based on the types and forms of soft-sediment deformation structures, including maximum liquefaction distance, thickness of disturbed layer, empirical formulae, and thickness of rapidly deposited sand layer. Then we discuss and analyze these methods in terms of their theoretical basis, advantages and disadvantages, accuracy, applicability and problems. We chose two case studies: first, a typical seismics-related deposit (liquefied layer and dsirupted layer) represented by a seismite in the late-Pleistocene Lake Lisan section near Masada in the Dead Sea Basin; and second, the liquefied diapir triggered by an earthquake in the late-Quaternary lacustrine sediments at Luobozhai in the upper reaches of the Minjiang River, east Tibet. The six methods listed above are employed to determine earthquake magnitudes associated with the seismics-related deposit and liquefied diapir, yielding magnitudes of 5.5-6.5 and 6-7, respectively. The combination of the six methods, provided a new and relatively convenient method for determining seismic shaking, especially in lacustrine sediments. This study can serves as a valid reference for comparing methods of calculating the magnitude of a paleoearthquake based on surface rupture parameters, and provides a better understanding of the long-term seismic activity and risk in tectonically active regions.

The deformation in the Late Quaternary sediments and development of Holocene tectonic landforms in the river basin are attributed to recent tectonic activities. The Geomorphic indices as tectonic indicators were used in the Luni-Sukri basin of south-western Rajasthan, traversed by faults and lineaments. Tectonically induced geomorphology and abnormal Relative Index of Tectonics (Iat) are present along the Marginal Fault (MF1), Neotectonic Faults (NeoF1 & NeoF2) and Minor Lineament 1 (ML1). The block tectonics in the basin is represented by Graben filled with more than 300m of Quaternary sediments bounded by Marginal Faults and Neotectonic Faults. The seismically deformed soft sediment deformation structures (SSDS) are present along faults separating horst and graben in the basin. From the optical ages of the sediments the seismic event is constrained between 1.44±0.2 ka and 0.12±0.03 ka which are possibly responsible for deformation and dislocation of sediments in the area.

This study was supported by Projects PID2019- 104625RB-I00 and PGC2018-098272-B-I00 (Secretaría de Estado de I+D+I, Spain), B-RNM-072-UGR18 (FEDER Andalucía), P18-RT-4074, and RNM-208 (Junta de Andalucía). Thanks to C. Sanz de Galdeano for his support in the field at the Alfarnate outcrop. We gratefully acknowledge the constructive comments of two anonymous reviewers., 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 sur faces, 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., Secretaría de Estado de I+D+I B-RNM-072-UGR18, European Regional Development Fund P18-RT-4074, RNM-208, Junta de Andalucía

Las sucesiones estratigráficas que constituyen el relleno de las cuencas neógenas de Las Minas de Hellín y Cenajo presentan numerosas evidencias de eventos derivados de inestabilidad tectónica. Son abundantes las estructuras de deformación sedimentaria a pequeña y mediana escala, como inyecciones de arena en filones, estructuras en champiñón, niveles de mezcla, laminación varvada disturbada y otras, que son interpretadas como respuesta a la actividad sísmica (sismitas). Aparte de estas estructuras, se reconocen depósitos resedimentados de gran escala, tales como macrobrechas y deslizamientos (slumps) de escala métrica a decamétrica, que también fueron debidos a movimientos sísmicos que afectaron a las cuencas durante su relleno. Otro aspecto considerado es la presencia de montículos carbonáticos parcialmente silicificados dentro de la sucesión estratigráfica de la Cuenca de Las Minas de Hellín, cuyo desarrollo estuvo estrechamente ligado a fallas a través de las cuales tuvo lugar la entrada de aguas termales.

Slump, breccias, and turbidite deposits interbedded with diatomaceous marlstone and limestone occur in the upper part of the Late Miocene lacustrine succession of the Cenajo and Las Minas Basins. The basins display half-graben geometries where the northern margins consist of a network of large and deep, listric normal faults. The largest single deformational unit, reaching up 40 m in thickness, crops out in the Cenajo Basin and consists of soft-sediment deformed slump deposits displaying a variety of fold styles and geometries. This represents possibly the largest slump body hitherto described in fossil lake systems. The amplitude of the folds varies from meters in major folds to centimeters in the intrafolial minor ones. Brittle deformation of the slump strata is also common and cross cuts the ductile fabrics. Measured major fold axial traces indicate preferential N-S to NW-SE slide movement. The predominant strain in the deformed deposits is simple shear. Outcrops in the Cenajo Basin allow observation of extensional structures at the head slide, large sheath, and recumbent folds in the intermediate zone and tight compression structures at the toe, where folds and thrusts overrun the slightly deformed down slope strata. In contrast, the slump deposits in the Las Minas Basin are seen to pass down-dip into breccia and turbidite beds, which is indicative of flow transformation and internal disaggregation of the folded beds with distance. A number of laterally linked turbidite facies are recognized in the uppermost resedimented unit of the Las Minas Basin. The occurrence of these deposits points to marked instability in the lake basins. This period was preceded and followed by pelagic sedimentation of varve-like laminated, diatom-rich deposits. Most probably, basin instability was related to earthquake shocks, perhaps coeval to the extrusion of volcanic lamproite rocks in the region during the late Tortonian.

This study discusses the composition and distribution of paleo-liquefaction structures, their triggering mechanisms, probable source and the dynamics of source faults expressed in the Kashmir basin (KB), NW Himalaya. Stratigraphic evidences of deformational structures along concomitant fault zones are highly preserved throughout the basin. The KB was frequently confronted with recurrent seismic activities along intra basinal active faults and adjacent active faults during differential uplift of Himalaya, which resulted in various deformation structures during and after the evolution of the KB. Past earthquake events released a significant part of the slip deficit along intra basinal active faults and vertically offset quaternary deposits by 1–3[Formula: see text]m and originated different and extensively deformation structures. In this context, stratigraphic sections and paleo-surface ruptures have been meticulously mapped to determine the seismic nature and the source of resultant causative earthquakes. The results of this study suggest that besides southern thrust systems, intrabasinal active faults are the main probable seismogenic sources responsible for development of these structures and play an important role in releasing the accumulated stresses in this region.

Intrastratal flow is a process that is still poorly understood, rarely described and difficult to interpret in ancient rocks. Sediments in the Cretaceous lacustrine Gyeokpori Formation of southwestern South Korea contain some chaotically deformed sandstone layers with deformed mudstone clasts that are ascribed to this process. The interpretation is based on the fact that these layers cannot be explained as a result of subaqueous debris flows or mass transport, whereas the sedimentary context, including the presence of other soft-sediment deformation structures, indicates that intrastratal flow must have been physically possible. The sedimentary setting was a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity caused seismic shocks that affected the unstable lake margins resulting in the dominance of gravity-flow deposits, but also in a high sedimentation rate that facilitated soft-sediment deformation partly caused by intrastratal flow. This must have happened fairly frequently during a probably limited time-span, as several layers showing traces of intrastratal flow are present within a succession of only

Loading processes and the resulting load structures induced by processes related to periglacial conditions are compared to those induced by seismic shocks. The load structures themselves are relatively easily recognizable but the responsible trigger mechanism is, though depending on the geological context, commonly difficult to establish. Load structures like load casts, pseudonodules, ball-and-pillow structures and flame structures are commonly ascribed to instable density gradients within sediments and to differential loading, but their formation always requires liquefaction. In glacigenic sediments, deformation structures have most commonly been ascribed to periglacial processes (as a type of cryoturbations), but it becomes ever more clear that glacigenic sediments can, particularly during ice-front fluctuations, be affected by faulting-related earthquakes (due to glacio-isostatic adjustment), and the thus triggered seismic shocks may result in deformations, including – most commonly – load structures. We inventory the evidence that may help to distinguish, on the basis of textural and structural features, load structures with a seismic origin from those that result from periglacial processes, taking into account that truly diagnostic criteria do not exist.

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.

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.

The Neoproterozoic Kansuki Formation in the Katanga Supergroup (Katanga Copperbelt, Democratic Republic of the Congo) mainly consists of platform carbonates with pyroclastic beds and mafic layers. Lithological and sedimentological investigation in the central part of the Katanga Copperbelt (Tenke Fungurume Mining District) evidenced peritidal facies for the carbonate. It also evidenced the presence of Soft Sediment Deformation Structures (SSDS). Small-scale load structures, multiple successions of load cast and flame structures are attributed to discrete sedimentary processes such as overloading and rapid deposition. Tepee-like structures are indicative of a subaerial exposure of the carbonate that was deposited in relatively shallow water. Major SSDS such as boudinage within water escape structures, load cast with attached pseudonodules, tepee-like structures with sheet cracks, small-scale mass displacement, and brecciation are interpreted as triggered by seismicity and indicative of active tectonics during sedimentation in the Katanga basin. This is consistent with the presence of pyroclastic beds and mafic layers within the Kansuki Formation, pointing to carbonate platform deposition in a paleorift.

The Lower Cretaceous Sao Sebastiao Formation of Jatoba Basin consists of continental strata accumulated in an arid environment dominated by aeolian deposits. The best outcrops are located in the county of Ibimirim, in the Pernambuco State. Through the description of several stratigraphic sections, three aeolian and two fluvial facies associations characterize this formation. The aeolian facies represent (a) aeolian crescentic dunes, (b) aeolian sand sheets, and (c) blowouts; the fluvial facies record (d) sheet floods and (e) channelized ephemeral rivers. These facies associations are organized into three genetic units that are bounded by supersurfaces. The unit 1 is formed by the intercalation of sheet flood, aeolian dry sand sheets, and aeolian dunes facies associations, often with soft sediment structures. The cross-bedded strata ascribed to aeolian dunes become larger and more frequent towards the top of the unit, as the soft sediment deformation structures become scarcer. The Unit 2 comprises aeolian sand sheets facies scoured by fluvial channels, with erosive concave bases, and by blowouts, which are subsequently filled by aeolian dunes deposits. Unit 3 consists of cross-bedded strata related to medium-to-large, either simple or compound aeolian dunes (draas). Supersurfaces bound the genetic units recording depositional gaps, thus defining different episodes of accumulation.

During the last years many studies focused on soft-sediment deformation structures (SSDS) to identify past seismic events. However, in regions that were affected by glaciations and periglacial processes like northern and central Europe, the use of SSDS as paleo-earthquake indicator is challenging. Interpretations require great care. Earthquakes are only one possible trigger mechanism of many that can cause liquefaction and/or fluidization of sediments, which leads to the formation of e.g. sand volcanoes, clastic dykes, flame structures, or ball-and-pillow structures.SSDS triggered by seismic shaking are so-called seismites. Originally the term ‘seismites’ was used by Sailacher (1969) and only referred to sediment beds that were deformed by earthquake-related shaking. Pleistocene seismites are described from former glaciated areas in Germany, Denmark, Sweden, Poland, Latvia, and Lithuania.However, ice-sheet loading, glaciotectonism as well as freeze and thaw processes in periglacial environments are also potential trigger mechanisms causing the formation of similar looking types of SSDS, which can be easily mistaken for seismites. Therefore, it is important to use a set of clear criteria to recognize seismites in the field.Extensive studies of Pleistocene sediments in northern Germany have shown that deformation bands are a suitable indicator for paleo-fault activity. Deformation bands that are developed close to the tip line of a fault in combination with e.g. sand volcanoes, clastic dykes, flame structures, or ball-and-pillow structures is the most robust indicator for paleo-earthquakes. References Seilacher, A. (1969). Fault-graded beds interpreted as seismites. Sedimentology, 13, 155-159.

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.

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.

During and shortly after the 2017 Pohang Earthquake (Mw 5.4), sand blows were observed around the epicenter for the first time since the beginning of instrumental seismic recording in South Korea. We carried out field surveys plus satellite and drone imagery analyses, resulting in observation of approximately 600 sand blows on Quaternary sediment cover in this area. Most were observed within 3 km of the epicenter, with the farthest being 15 km away. In order to investigate the ground’s susceptibility to liquefaction, we conducted a trench study of a 30 m-long sand blow in a rice field 1 km from the earthquake epicenter. The physical characteristics of the liquified sediments (grain size, impermeable barriers, saturation, and low overburden pressure) closely matched the optimum ground conditions for liquefaction. Additionally, we found a series of soft sediment deformation structures (SSDSs) within the trench walls, such as load structures and water-escaped structures. The latter were vertically connected to sand blows on the surface, reflecting seismogenic liquefaction involving subsurface deformation during sand blow formation. This genetic linkage suggests that SSDS research would be useful for identifying prehistoric damage-inducing earthquakes (Mw > 5.0) in South Korea because SSDSs have a lower formation threshold and higher preservational potential than geomorphic markers formed by surface ruptures. Thus, future combined studies of Quaternary surface faults and SSDSs are required to provide reliable paleoseismological information in Korea.

It is hitherto commonly thought that earthquakes triggered by geologically rapid changes in the pressure caused by the fluctuating extent of thick land-ice masses occur exclusively during ice retreat. Our study of deformed sediment layers within an undeformed glaciolacustrine and glaciofluvial succession exposed in a coastal cliff on Rugen Island, south-western Baltic Sea, challenges this widespread idea. Based on their structural and deformational features, the layers under investigation are interpreted as seismites which formed as a result of seismically-induced liquefaction. The stratigraphic context aided by optically stimulated luminescence (OSL) dating indicate that the documented seismites must have formed shortly before the front of the Pleistocene Scandinavian Ice Sheet reached the study area during the Last Glacial Maximum, thus during a stage of ice advance. This implies that the flexural isostatic response of the Earth's crust as a consequence of the ice load during ice advance was accompanied by earthquakes probably due to local re-activation of pre-existing faults. The crustal response to an increasing ice load was consequently less gradual than previous studies about glaciation-related tectonics suggest.

Earthquakes-related soft-sediment deformations (seismites) are relevant structures to help reconstructing the palaeoseismicity in a region. Nevertheless, although seismites have been described for a large variety of palaeo-environments and stratigraphic settings, they are rare and, in some cases, ambiguous structures. In this paper, we document, for the first time, impressive seismites affecting a latest Quaternary travertine deposit located in southern Tuscany (Serre di Rapolano, Italy). These structures are extremely relevant, as seismites have been never described for this kind of terrestrial deposits. The seismites developed within a 2.5 m thick stratigraphic succession made of alternating terrigenous and carbonate sediments, embedded within the travertine deposits. Earthquake produced liquefaction and fluidization of some terrigenous levels and the injection of fluidized silty sediments (dykes and sills) into carbonate and terrigenous levels; slumped levels and associated decollement surfaces produced highly non-cylindrical folds, overall induced by the loss of brittle shear strength along the basin slopes. The occurrence of these soft-sediment deformations implies an important seismic event that took place in a time spam encompassed between 84 ± 8 and 48.92 ± 5.08 ka, in an area characterized by low seismicity and scarce knowledge of its seismotectonic setting. Their spectacular exposition and preservation in saw-cuts of an abandoned quarry (Cava Oliviera quarry) highlights their relevance and importance.

Recent uplift in the NW Himalaya has exposed more than 1000 m of the Plio-Pleistocene so-called Karewa deposits in Kashmir. These deposits mostly consist of horizontal-stratified sand, silt, clay, conglomerates, and lignite beds. The sedimentary succession belongs to the Kashmir basin that is located in a seismically active zone. The area was previously affected by large earthquakes. The observed soft-sediment deformation structures (SSDS) are predominantly developed in the sand, silt and clay beds; and include load and water escape structures, intrusive sedimentary bodies, convolute bedding, disturbed laminites, and slump structures. Deformation mechanism and driving forces of the SSDS were seismic shock waves. Sediment loading and storm events as driver for the SSDS are less likely and the proximity of the SSDS to faults underlines the seismic origin of these structures. Syn-and post-depositional faults and deformation bands developed in the Karewa deposits support the interpretation of neotectonic activity and point to an earthquake of magnitude >5.5 that struck the Kashmir basin in the Plio-Pleistocene.

An exposure of the Paleoproterozoic Gordon Lake Formation in the Bruce Mines area, Ontario, Canada, contains abundant soft-sediment deformation structures (SSDS), including load casts, convolute bedding, pseudonodules, ball-and-pillow structures, flame structures and one dewatering pipe. These features are developed in siltstone to fine-grained sandstone beds and are between 1 and 120 cm in width and 3–78 cm high. The primary trigger mechanism is interpreted to be storm or tsunami activity, however seismic shock, overloading brought about by density inversions, or a combination of these processes, may have influenced the formation of SSDS to a lesser degree. Several beds also contain flat to wavy carbonaceous laminae, locally with a botryoidal texture and concentrations of heavy minerals, which are interpreted as relicts of microbial mats. Microbial mats may have played a minor role in the formation of SSDS, but do not appear to have been a prominent driving mechanism. Soft-sediment deformation structures observed in the Baie Fine, Flack Lake, and Cobalt plains regions of Ontario, are smaller and not as abundant as in the study area, suggesting that the deposits in the study area were either affected by local events or different magnitudes of sedimentary processes. In contrast to the tidal flat paleoenvironment interpreted for the Gordon Lake Formation in the Flack Lake area, the stratigraphically lower beds at the studied outcrop more closely resemble shallow shelf deposits.

The Sorgenfrei-Tornquist Zone (STZ) is the northwestern segment of the Tornquist Zone and extends from Bornholm across the Baltic Sea and northern Denmark into the North Sea. It represents a major lithospheric structure with a significant increase in lithosphere thickness from south to north. A series of meter-scale normal faults and soft-sediment deformation structures (SSDS) are developed in Lateglacial marine and lacustrine sediments, which are exposed along the Lønstrup Klint cliff at the North Sea coast of northern Denmark. These deformed deposits occur in the local Nørre Lyngby basin that forms part of the STZ. Most of the SSDS are postdepositional, implying major tectonic activity between the Allerød and Younger Dryas (∼14 ka to 12 ka). The occurrence of some syn- and metadepositional SSDS point to an onset of tectonic activity at around 14.5 ka. The formation of normal faults is probably the effect of neotectonic movements along the Børglum fault, which represents the northern boundary fault of the STZ in the study area. The narrow and elongated Nørre Lyngby basin can be interpreted as a strike-slip basin that developed due to right-lateral movements at the Børglum fault. As indicated by the SSDS, these movements were most likely accompanied by earthquake(s). Based on the association of SSDS these earthquake(s) had magnitudes of at least Ms ≥ 4.2 or even up to magnitude ∼ 7 as indicated by a fault with 3 m displacement. The outcrop data are supported by a topographic analysis of the terrain that points to a strong impact from the fault activity on the topography, characterized by a highly regular erosional pattern, the evolution of fault-parallel sag ponds and a potential fault scarp with a height of 1–2 m. With finite-element simulations, we test the impact of Late Pleistocene (Weichselian) glaciation-induced Coulomb stress change on the reactivation potential of the Børglum fault. The numerical simulations of deglaciation-related lithospheric stress build-up additionally support that this neotectonic activity occurred between ∼14.5 and 12 ka and was controlled by stress changes that were induced by the decay of the Scandinavian ice sheet. In the Holocene, the stress field in the study area thus changed from GIA-controlled to a stress field that is determined by plate tectonic forces. Comparable observations were described from the central STZ in the Kattegat area and the southeastern end of the STZ near Bornholm. We therefore interpret the entire STZ as a structure where glacially induced faulting very likely occurred in Lateglacial times. The fault reactivation was associated with the formation of small fault-bound basins that provided accommodation space for Lateglacial to Holocene marine and freshwater sediments. © 2018 The Authors

We investigate episodic soft-sediment deformation structures cross-cut by normal faults preserved in unlithified finely laminated calcite rich sediments in the Hirlatz cave in the Northern Calcareous Alps (Austria). These sediments comprise varve-like alternations of brighter carbonate/quartz rich layers, and darker clay mineral rich layers. The deformed sediments contain abundant millimeter to centimeter-scale soft-sediment structures (load casts, ball-and-pillow structures), sheet slumps (thrust faults and folds), erosive channels filled with slides and chaotic slumps. After deposition and soft-sediment deformation normal faults developed within the entire sedimentary succession, an event that probably correlates with an offset of c. 10 cm of the passage wall above the outcrop. Our major conclusions are: (i) The sediments have a glacial origin and were deposited in the Hirlatz cave under phreatic fluvio-lacustrine conditions. The deposition and the soft-sediment deformation occurred most likely during the last glaciation (i.e. around 25 ka ago); (ii) The liquefaction and formation of the soft-sediment structures in water-saturated stratified layers was triggered by episodic seismic events; (iii) The internally deformed sediments were later displaced by normal faults; (iv) A possible source for the seismic events is the active sinistral Salzach-Ennstal-Mariazeller-Puchberger (SEMP) strike-slip fault which is located about 10 km south of the outcrop and plays a major role in accommodating the extrusion of the Eastern Alps towards the Pannonian Basin. To our knowledge, the described structures are the first report of liquefaction and seismically induced soft-sediment deformations in Quaternary sediments in the Eastern Alps.

Cavities produced by migrating gas, mainly methane, emanating from the near subsurface are a rarely reported sedimentary structure from either modern or ancient clastic sediments. The delta of the Colorado River in Lake Powell, Glen Canyon National Recreation Area provides an excellent recently accessible locality for examining soft sediment deformation structures generated by escaping gases and fluids. Sub-meter-scale to tens-of-meter-scale structures, including craters, salses, and sand and mud volcanoes are present on the modern Lake Powell delta. Abundant sub-centimeter-scale cavities are found in excavations through crater sediments and exposed along cut-bank exposures of the Colorado River. In cross section the cavities are subvertical, irregular-to sigmoidal-to lenticular-shaped, 1–3 mm short axes, up to ∼3.0 cm long axes, and ∼1 cm intermediate axes. Cavities are developed in cm-scale, laminated silty clay and clay graded beds. The tops of the cavities are wider than their bases. The cavities observed in the Lake Powell delta are interpreted as mode 1 fractures and probably represent a clastic morphologic analog to ‘molar-tooth’ carbonate structures. The characteristics of the cavities, and the geometries and deformation of the surrounding delta-mud host, are consistent with bubbles and fracturing generated by gas migration experiments and theoretical calculations but vary because of inherent heterogeneity of the sediments. Fractures developed as gas migrated into pre-existing cavities causing overpressure in cavities and leading to subvertical mode 1 fracture propagation. Recent sudden decompression related to rapid lake level drops of Lake Powell may have enhanced the release of gas, primarily bacterially produced, leading to the development of these soft sediment deformation structures.

The Paso Córdoba fossiliferous site (Río Negro, Northern Patagonia) is one of the first Mesozoic fossiliferous localities studied in Argentina. There, turtle, crocodile and dinosaur remains as well as dinosaur and bird tracks have been recorded. Recently, a new locality with vertebrate tracks, the Cañadón del Desvío, has been discovered in Paso Córdoba. Six track-bearing layers were located in outcrops belonging to the Anacleto (lower to middle Campanian, Neuquén Group) and Allen (middle Campanian-lower Maastrichtian, Malargüe Group) formations. The Cañadón del Desvío locality reveals that vertebrate trace fossils are distributed in two distinct environments, floodplains of a meandering fluvial to shallow lacustrine system and a wet interdune deposit that is associated to an aeolian setting. Also, in the logged section several soft sediment deformation structures were found. In regard of this, a sedimentary facies analysis is provided in order to assess the palaeoenvironmental implications of this new record. The analysed tracks are preserved in cross-sections, on bedding-planes and as natural casts. When it is possible, the tracking surface, true tracks, undertracks and overtracks/natural casts have been identified and the track preservation and the formation history of the tracksite are discussed. Only two tracks preserve enough anatomical details to relate them with their trackmakers, in this case hadrosaurid dinosaurs. The stratigraphical, facial and palaeoenvironmental data of this study support the idea of a transitional passage between the Anacleto and Allen Formation in Paso Córdoba. The presence of hadrosaurid dinosaur tracks suggests that the upper part of the log, where this kind of tracks were found, likely belong to Allen Formation due to this dinosaurs appear in the Southern Hemisphere in this epoch. The sum of osteological and ichnological remains improve the Paso Córdoba palaeofaunistic knowledge. The presence of six different levels in which the trackmakers walked reflects the abundance of vertebrates in the transition between Anacleto and Allen formations. Fil: Díaz Martínez, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Cónsole Gonella, Carlos Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina Fil: de Valais, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Salgado, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro; Argentina

The study documents soft-sediment deformation structures (SSDSs) in the lacustrine Dongying Depression, a Paleogene synrift basin located in the southeastern corner of the Bohai Bay Basin, East China. The focus of this study is the lower part of the upper 4th member of the Eocene Shahejie Formation (Es4U), characterized by littoral to sublittoral deposits in the southwestern Dongying Depression. Nine lithofacies are grouped into the upper shoreface facies associations (FA1-1), lower shoreface facies associations (FA1-2), and sublittoral facies associations (FA2). Fine-grained calcareous sandstone was mainly deposited in FA1-1, with thinly alternating calcareous mudstone and siltstone or sandstone in FA1-2, while deposition in FA2 was dominated by mudstone, containing sediment gravity flow deposits. The SSDSs widely encountered in the lower Es4U can be classified into seven categories: (1) load structures, (2) water-escape structures, (3) folds and convolute lamination, (4) sediment-injection structures, (5) microfaults, (6) autoclastic breccias, and (7) slumps. Detailed observations of SSDSs from cores indicate liquefaction and fluidization as the main deformation mechanisms in the sands and muds. Moreover, rupturing of cohesive deposits also contributes to the soft-sediment deformation. The types and morphologies of the SSDSs are closely related to the rheologies of the sediments (e.g., the sand content), influenced by the facies that determine the lithologies and stratigraphic stacking patterns. Except for some deformation structures related to subaqueous sediment gravity flows (e.g., muddy debrite flows and slumps), most SSDSs are ascribed to rift-related seismicity due to the activity of the adjacent synsedimentary faults when the Dongying Depression underwent quick subsidence during the Eocene.

Soft-sediment deformation structure crops out in the Upper Triassic carbonate succession of Messaoudi Formation in the north eastern of Tataouine basin (south eastern Tunisia). The deformed interval is about 10 m thick and tack place between shallow-water limestone and stromatolitic bed. Soft-sediment deformation structures (slump), supareted by undeformed beds include boudins, pinch-and-swell structure, and normal faults and folded structures. Observations and measurements of the deformed structure and bed thickness of hinges and limbs indicate that all the deformed structures are related to slump structure, which affects unconsolidated sediment in the local paleo-slope. The internal mechanisms are ruled out due to the absence of features (high sediment rate, traction feature, chemical process). The slump was triggered by external mechanisms; tectonic effects related to the reactivation of EW faults during the opening movements of the paleotethys. These tectonic events generat a moderat seismic activity wich affected unconsolidated sediment.

Turbidites of the Early Cretaceous Lingshandao Formation on Lingshan Island, eastern China, show numerous soft-sediment deformation structures. The turbidites accumulated in a rift basin plain on the distal part of a low-energy fan, together with autochthonous fine-grained sediments that settled from suspension. Occasionally, sets of both types of sediments slumped down the basin slope. The turbidites were studied in two sections. Paleocurrent directions, measured from sole marks at the base of the sandy turbidites, indicate a slope from SE to NW; this is consistent with the dip direction of the axial planes of the major slump folds. Among the numerous types of soft-sediment deformation structures that are present, two types are of special interest because of their specific genesis, viz. rip-up clasts and dome structures. It appears that rapid sedimentation must be considered as the main trigger behind these deformations: the rapid accumulation of particularly the sandy turbidites resulted in overloading of the underlying beds and then consequently in an increase in their pore-water pressure that induced liquefaction and fluidization, which triggered the formation of the rip-up clasts and dome structures. The downslope movement of freshly deposited turbidites after slope failure over the inclined sedimentary surface induced shear stresses, which resulted in the complication of the rip-up clasts and the preferred orientation of some dome structures. Both the dip directions of the axial planes of some of the dome structures and microfolds within the rip-up clasts are consistent with the paleocurrent direction indicated by the sole marks and the slump folds.

Soft sediment deformation structures (SSDS) are preserved in a homogenous dolomudstone lithology of crinkly laminated and heterolithic facies of the Paleoproterozoic Vempalle Formation in the Cuddapah Basin. This basin was formed on the eroded basement rocks of the Eastern Dharwar Craton, India. Deformation structures preserved in this succession include combination of breccia and folds, intrastratal faults, cracks, and dikes belonging mostly to a brittle deformation regime associated with ductile imprints. Based on the observed SSDS, their lateral homogeneity and traceability, draping by undeformed strata, proximity of faults as well as apparent lack of storm signatures and gravity induced mass movement, these fine-grained deformed beds can be tentatively ascribed to a large to intermediate depth earthquake with Richter magnitude scale 4 and above, generated during reactivation of basement faults owing to plume related mantle activity. The occurrence of SSDS in the Vempalle Formation emphasizes the role of downwarping along pre-existing planes of weakness in the Archean basement in the evolution of the Cuddapah Basin, analogous to subsidence in present-day continental margin.

Made available in DSpace on 2022-05-01T07:58:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras The Lower Cretaceous Araripina Formation records deposition in a distributive fluvial system that is a part of the post-rift sequence of the Araripe Basin, NE Brazil. Following the opening of the Brazilian Equatorial Margin, the reactivation of regional faults of the Paleoproterozoic basement resulted in tectonic subsidence and formation of a regional-scale DFS. The Araripina Formation is an up to 40-m-thick succession of rhythmically interbedded sandstone and mudstone, organized in two depositional sequences separated by a regional disconformity. We recognized and grouped nine sedimentary facies into six facies associations that we interpreted as deposits of meandering channels, ribbon channels, minor channels, floodplain, lateral and terminal splays, and distal floodplain. The lower sequence facies associations suggest deposition in the medial to distal part of a distributive fluvial system in a tectonically active, interior basin subjected to episodic flooding. The periodic inundations were responsible for activating ephemeral channels and producing sheetfloods, followed by deposition of lateral and terminal splays in distal flooded areas. Syn-sedimentary deformation structures are present in rhythmite facies (truncating surfaces, load structures, injectite and convoluted folds) in the upper part of the lower sequence. The upper sequence was formed after a period of intense tectonic activity in a large distal floodbasin dominated by suspension. The deposition culminates in an interval with pedogenetic deposits cross-cut by a regional disconformity with the upper Exu Formation. Paleocurrent data from both depositional sequences indicate paleodepositional slope towards southeast and east with source-areas located to the northwest and west. This pattern is similar to that observed in the lower Santana Group and opposite to the westward direction of sedimentary transport in the overlying Exu Formation implying significant change of source region, basin topography and continental paleodrainage in the Araripe Basin after the Albian. Department of Geology IGCE São Paulo State University, Avenida 24A, 1515 Department of Geology School of Mines Federal University of Ouro Preto, Morro do Cruzeiro CECS Federal University of ABC, Avenida dos Estados, 5001 Geography Institute Federal University of Uberlândia, Rodovia LMG-746 Km 01 Department of Geology IGCE São Paulo State University, Avenida 24A, 1515

At a Pliocene methane seep site in Taiwan characterized by numerous tubular carbonate bodies and bivalves, a half meter-long dolomitic concretion containing a lucinid bivalve Anodontia goliath reveals the impact of chemosymbiotic bivalves on fluid migration through shallow sediments. The concretion consists of a cortex encasing a central channel filled with sparite and varying amounts of brecciated material derived from the channel walls. The studied bivalve is preserved with the hinge upward. When restored to life position, the central channel is connected to the anterior side of the bivalve. In the lower longer segment, the channel is connected to the posterior sector of the bivalve. The channels are interpreted as the anterior tube for supply of respiration water and the posterior tube for mining sulphide generated in the sulfate-methane transition zone of the sediment. The dolomitic cortex surrounding the central channel is characterized by δ13C values as low as −29‰ VPDB, indicating that the rate of anaerobic oxidation of methane was enhanced around the conduit. At the base of the central channel, upward soft sediment deformation structures likely resulted from the dragging effect when fluid migrated out of the sediment and entered the channel. Brecciation of the channel walls indicates pulsating seepage during the incipient stages of cementation. The burrow, thus, acted as a highly permeable conduit channeling upstreaming methane-charged fluid for a substantial period of time. Therefore, burrows can be efficient in pre-determining the formation of fluid conduits at seep sites, having potentially a large impact on fluid mixing and diagenetic reaction rates in sediments, and ultimately the amount of methane released. The reported bivalve with its conserved burrow fossilized as seep carbonate concertion provides direct evidence that fluid conduits form along animal burrows.

Soft-sediment deformation structures are present within the deep-marine fan of the West Crocker Formation, Sabah Basin, NW Borneo. Focus of this study is to highlight the impact of seismic and aseismic activities on the development of these structures and their distribution in deep-marine fan. Twenty-nine types of deformation structures were identified during the study of twelve exposed sections. These structures were grouped into five categories: i) water-escape structures, ii) sole marks, iii) clastic intrusions, iv) deformed laminations, and v) syn-depositional brittle and ductile deformation structures. The sediment deformation is interpreted to be caused either by aseismic processes like slope failure, gravity collapse, sediment overloading, density gradient, seismic induced mechanisms such as earthquakes, tectonic uplift, or combined effect of seismic and aseismic events. These structures are classified based on type of features developed during semi-consolidated phase of rock deposition. The seismite structures i.e., clastic intrusions, deformed laminations, and syn-depositional structures are correlated with active collisional tectonics during the Late Paleogene times in the Sabah Basin. In the present work, a generalized conceptual model has also been proposed for the development of soft-sediment deformation structures in a submarine fan environment. Dewatering structurers and rapid sedimentation features are associated with inner fan, load and flame structures are present within middle fan, while contorted layers, slumps and mass-transport deposits are linked with distal fan settings.

The geomorphic, tectonic and seismic aspects of the Ganga plain have been studied by several workers in the recent decades. However, the northern part of this tectonically active plain has been the prime focus in most of the studies. The region to the south of the Ganga River requires necessary attention, especially, regarding the seismic activities. The region lying immediately south of the Outer Himalayas (i.e. the Ganga plain) responds to the stress regime of the Himalayan Frontal Thrust Zone by movement along the existing basement faults (extending from the Indian Peninsula) and creating new surface faults within the sediment cover as well. As a result, several earthquakes have been recorded along these basement faults, such as the great earthquakes of 1934 and 1988 associated with the East Patna Fault. Large zones of ground failure and liquefaction in north Bihar (close to the Himalayan front), have been recorded associated with these earthquakes. The present study reports the soft sediment deformation structures from the south Bihar associated with the prehistoric earthquakes near the East Patna Fault for the first time. The seismites have been observed in the riverine sand bed of the Dardha River close to the East Patna Fault. Several types of liquefaction-induced deformation structures such as pillar and pocket structure, thixotropic wedge, liquefaction cusps and other water escape structures have been identified. The location of the observed seismites within the deformed zone of the East Patna Fault clearly indicates their formation due to activities along this fault. However, the distance of the liquefaction site from the recorded epicenters suggests its dissociation with the recorded earthquakes so far and hence possibly relates to any prehistoric seismic event. The occurrence of the earthquakes of a magnitude capable of forming liquefaction structure in the southern Ganga plain indicates the transfer of stress regime far from the Himalayan front into the peninsular region through these basement faults. Northward extension of the East Patna Fault coincides with the region of the Himalayan front, which corresponds to a less slip potential. Therefore, an association of frequent earthquakes in this region indicates strain release along the East Patna Fault.

Fine-grained sediments from the Late Triassic Yanchang Fm. in the Ordos Basin (central China) were studied by core analysis and geophysical logging. Part of the mudstones in this formation are stratified, part of them are unstratified; the various mudstones can be subdivided into eight types on the basis of their structures and textures. They represent a variety of environments, ranging from delta fronts and subaqueous fans to deep-water environments. Part of the sediments were reworked and became eventually deposited from subaqueous gravity flows, such as mud flows, turbidity currents and hyperpycnal flows that easily developed on the clay-rich deltaic slopes. The sediments deposited by such gravity flows show abundant soft-sediment deformation structures. Understanding of such structures and recognition of fine-grained sediments as gravity-flow deposits is significant for the exploration of potential hydrocarbon occurrences. Because fine-grained deposits become increasingly important for hydrocarbon exploration, and because the sediments in the lacustrine Yanchang Formation were deposited by exactly the same processes that play a role in the accumulation of deltaic and prodeltaic fine-grained sediments, the sedimentological analysis provided here is not only important for the understanding of deep lacustrine sediments like the Yanchang Formation, but also for a better insight into the accumulation of fine-grained prodeltaic deep-marine sediments and their potential as hydrocarbon source rocks and reservoir rocks.