The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help recon...The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.展开更多
Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist ...Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time: large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.展开更多
The unequivocal identification of soft-sediment deformation structures(SSDS)is a significant attribute to constrain the effect of transient geological events in the spatio-temporal evolution of ancient sedimentary bas...The unequivocal identification of soft-sediment deformation structures(SSDS)is a significant attribute to constrain the effect of transient geological events in the spatio-temporal evolution of ancient sedimentary basins.This paper reports and discusses,for the first time,the occurrence of several cm-to dm-scale SSDS within sandstone successions of the Mesoproterozoic Kaimur Group(Vindhyan Supergroup),exposed at the Hanumandhara Hill of Chitrakoot-Satna border region,Madhya Pradesh State,India.The SSDS are confined to a deformed interval comprising seven individual sedimentary units of variable composition and texture,which are sandwiched between nearly horizontally undeformed sandstone beds.The SSDS consist of load structures(load casts,flame structures,pseudonodules and ball-and-pillow structures),contorted lamination,convolute lamination,boudins and pinch-and-swell structures,deformed cross-stratification,slump structures,clastic injections,fluid escape structures,and syn-sedimentary fractures/faults.The pre-sent study suggests that the formation of these SSDS is essentially related to a combination of processes(gravitational instability,liquefaction,fluidization,and fluid escape)predominantly induced by seismic shocks.In addition,the restricted occurrence of fractures/faults in these deformed layers emphasizes the passage of seismically-induced Rayleigh waves.Considering the observed types of SSDS,their lateral homo-geneity and geographic distribution along with the geodynamic framework of the Vindhyan Basin,the whole area can be tentatively attributed to having experienced moderate-to high-magnitude(M≥5)seismicity.The present study combined with earlier reports of seismically-induced SSDS,from other regionally disposed formations belonging to the Lower(e.g.,Kajrahat Limestone,Chopan Porcellanite,Koldaha Shale,Rohtas Limestone,and Glauconitic Sandstone of the Semri Group)and Upper(e.g.,Bhander Limestone of the Bhander Group)Vindhyan Supergroup,respectively,provides evidence for the constant regional-scale seismo-tectonic activity within the Paleo-Mesoproterozoic Vindhyan Basin.Importantly,this observation further suggests that the intracratonic basins can be active tectonically contrary to the earlier propositions.展开更多
The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal envir...The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal environment that was ideal for recording earthquakes in the form of soft-sediment deformation structures (SSDS). Numerous examples occur in the upper part of the Wumishan Formation, along the Yongding River Valley. In addition, brittle structures include intrastratal fault and seismically cracked breccias. The soft-sediment deformation structures include liquefied features (diapirs, clastic dykes, convolute bedding), compressional deformation features (accordion folds, plate-spine breccias, mound-and-sag structures), and extensional plastic features (loop-bedding). Based on the regional geological setting and previous research, movements along the main axial fault of the Yan-Liao aulacogen are considered as the triggers for earthquakes since the Early Mesoproterozoic. The number and distribution of the SSDS suggest the major earthquake frequency in the Wumishan Formation of 20 to 32 thousand years.展开更多
The Nihewan Basin is a rift basin at the junction of northern Shanxi Province and northwestern Hebei Province in north China.The basin is known for its rich paleontological fossils and ancient human remains.There are ...The Nihewan Basin is a rift basin at the junction of northern Shanxi Province and northwestern Hebei Province in north China.The basin is known for its rich paleontological fossils and ancient human remains.There are also abundant soft-sediment deformation structures(SSDS)in the thick lacustrine sediments.Previously,most SSDS have been interpreted as ice-edge features or ignored entirely.Recently,the authors have carried out several field surveys in the Nihewan Basin and found that many SSDS are sandwiched between normal lacustrine strata at multiple sections.In the excavation pit at the 10th Locality of Maliang Site(ML10),10 horizontal SSDS layers and two vertically developed geological features have been identified.Based on genesis analysis and related criteria,these features are divided into two categories:cryoturbation-triggered SSDS and earthquake-triggered SSDS.Among them,a special type of ancient ice-wedge pseudomorph(SSDS-8)of ML10 is recognized in the basin for the first time.The other 9 horizontal SSDS are mainly caused by earthquake-triggered liquefaction and slumping.They can be further divided into 14 seismic event layers.These findings indicate that the tectonic activity in the Nihewan Basin is very strong and frequent,and there were cold periods in the geological history of the basin.At the same time,the SSDS with distinct morphological characteristics and stable horizontal distribution in the basin can be used as an important indicator of stratigraphic correlation.展开更多
The salt beds of the Middle-Lower Cambrian are widespread in the middle-west parts of the Central Uplift and adjacent areas, the Tarim Basin. This paper presents the results of seismic interpretation and drilling data...The salt beds of the Middle-Lower Cambrian are widespread in the middle-west parts of the Central Uplift and adjacent areas, the Tarim Basin. This paper presents the results of seismic interpretation and drilling data analysis, which discovered that the salt beds were formed in an old geologic age, deeply buried, with relatively small scaled flowing and gathering and uneven distribution. As the regional detachment layers, the salt sequences considerably control the structural deformation of the up-salt Paleozoic, forming a series of hydrocarbon traps. In due course, the salt beds of the Middle-Lower Cambrian provide excellent cap rocks and trap conditions; thus the value of exploring hydrocabon reservoir in the target strata of the sub-salt Sinian- Cambrian is greatly increased. Research has shown that the salt-related structures of the Middle-Lower Cambrian in the area mainly exist in the form of salt pillow, salt roller, up-salt anticline, salt diapir, assemblage of the salt arch and up-salt fault-block, assemblage of basement fault and salt anticline, assemblage of the basement fault-block and salt dome, assemblage of salt detachment and fault-related fold, and assemblage of basement fault-block, salt arch and up-salt imbricated thrusts. The evolution and deformation mechanisms of the salt-related structures are controlled largely by basement faulting, compressional shortening, plastic flowing and gathering, superstratum gravitation, and up-salt faulting and detaching. They are distributed in rows or belts along basement faults or fault block belts.展开更多
An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersec...An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault,Second Songhua River Fault and Fuyu North Fault which lies northwest of TanchengLujiang Fault(Tan-Lu Fault).The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter,caused serious disasters to the local surroundings.The visible liquefied structures include sand volcanoes,liquefied sand mounds,sand dikes and sand sills.Sand volcanoes can be divided into sand volcano with a crater,sand volcano without a crater and water volcano(no sand).Other soft-sediment deformation structures(SSDS)induced by the earthquake include deformation lamination,load and flame structures,deformation folds,dish structures,convolute bedding and water-escape structures.The formation process of the sand volcanoes comprises three stages:(1)building up excess pore-fluid pressure in the liquefied layer,(2)cracking of the low-permeable overlying layer,and(3)mixture of sand-water venting out of the ground surface.During the upward movement,the liquefied sand is injected into the low-permeable layer to form sand veins,sand sills and various types of deformation structures.Vertical distribution of seismic liquefaction structure can be divided into four zones:the thoroughly liquefied zone,the lower liquefied zone with SSDS,the upper liquefied zone with SSDS,and the ground surface liquefied zone.The liquefaction occurred at a burial depth of 2–5 m,and the thickness of liquefied sand is 2 m.NE-SW(35°–215°)trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault(Fuyu/Songyuan-Zhaodong Fault)to reactivate.The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disasterprone areas.Meanwhile it provides abundant basic material for studying earthquake-induced SSDS in both ancient and modern sediments.The research is obviously of great significance to reveal that the northern Tan-Lu Fault has entered a stage of active seismic activity since the twenty-first century.展开更多
In capturing a snapshot of 150 years(1872-2022)of research on deep-water processes,deposits,settings,triggers,and deformation,the following 22 topics are selected:(1)H.M.S.Challenger expedition(1872-1876):The discover...In capturing a snapshot of 150 years(1872-2022)of research on deep-water processes,deposits,settings,triggers,and deformation,the following 22 topics are selected:(1)H.M.S.Challenger expedition(1872-1876):The discovering of the“Challenger Deep”by the H.M.S.Challenger in the Mariana Trench has been the single most important achievement in deep-water research.(2)Five pioneers amid 50 notable contributors:R.A.Bagnold,J.E.Sanders,G.D.Klein,F.P.Shepard,and C.D.Hollister.(3)Mass transport:Mass-transport deposits(MTD)are the most important deep-water facies in terms of volume,geohazards,and petroleum reservoirs.(4)Gravity flows:There are six basic types,namely(a)hyperpycnal flows,(b)turbidity currents,(c)debris flows,(d)liquefied/fluidized flows,(e)grain flows,and(f)thermohaline contour currents.Sandy debrites are the most important petroleum reservoir facies.Despite their popularity,turbidites are not an important reservoir facies.(5)Kelvin-Helmholtz(KH)waves:Turbidites,related to KH waves,with internal hiatus are not qualified to function as predictive facies models;nor are they fit for stratigraphic correlations.(6)High-density turbidity currents(HDTC):Misclassification of density-stratified gravity flows with laminar debris flows and turbulent turbidity currents as HDTC is flawed.Experimental generation of density-stratified gravity flows in flume studies has debunked the concept of HDTC.(7)Classification of turbidites:Contrary to the popular groupthink,turbidites are exclusive deposits of turbidity currents.(8)Bottom currents:The four basic types of deep-marine bottom currents are:(a)thermohaline-induced geotropic contour currents,(b)wind-driven bottom currents,(c)tide-driven bottom currents(mostly in submarine canyons),and(d)internal wave/tide-driven baroclinic currents.(9)Classification of contourites:Contrary to the popular groupthink,contourites are the exclusive deposits of thermohaline-induced geotropic contour currents.(10)Tidal currents in submarine canyons:Their velocity measurements have been the single most important achievement in deep-water process sedimentology.(11)Modern and ancient systems:There is a dichotomy between rare observations of turbidity currents in modern settings and overwhelming cases of interpretations of ancient turbidites in outcrops and cores.The reason is that turbidity currents are truly rare in nature,but the omnipotent presence of turbidites in the ancient rock record is the manifestation of groupthink induced by the turbidite facies model(i.e.,the Bouma Sequence).(12)Internal waves and tides:Despite their ubiquitous documentation in modern oceans,their ancient counterparts in outcrops are extremely rare.This is another dichotomy.(13)Hybrid flows:They are commonly developed by intersecting of down-slope gravity flows with along-slope contour currents.However,they are often misapplied to down-slope flow transformation of gravity flows.(14)Density(sediment)plumes:Deflected sediment plumes by wind forcing are common.Despite their importance in provenance studies,they are not adequately studied.(15)Hyperpycnal flows:They occur near the shoreline,next to the plunge point;but are of no relevance in deep-water environments.However,their importance in deep-marine settings is overhyped in recent literature.(16)Omission of erosional contact and internal hiatus:In order to promote genetic facies models that must not contain internal hiatuses,some researchers selectively omit internal hiatuses observed by the original authors.(17)Triggers of sediment failures:There are 22 types,but short-term triggers,such as earthquakes and meteorite impacts are more important than the conventional long-term trigger known as Eustasy.(18)Tsunami waves:Despite their sedimentologic importance,there are no reliable criteria for recognizing tsunami deposits in the ancient rock record.(19)Soft-Sediment Deformation Structures(SSDS):Although most SSDS are routinely interpreted as seismites,not all SSDS are caused by earthquakes.There are 10 other mechanisms,such as sediment loading,which can trigger liquefaction that can develop SSDS.(20)The Jackfork Group,Pennsylvanian,Ouachita Mountains,USA:Our reinterpretation of this classic North American flysch turbidites as MTD and bottomcurrent reworked sands has resulted in the longest academic debate with 42 printed pages in the AAPG Bulletin history since its founding in 1917.(21)Basin-floor fan model,Tertiary,North Sea:Our examination of nearly 12,000 ft(3658 m)of conventional core from Paleogene and Cretaceous deep-water sandstone reservoirs cored in 50 wells in 10 different areas or fields in the North Sea and Norwegian Sea reveals that these reservoirs are predominantly composed of MTDs,mainly sandy slumps and sandy debrites,and bottom-current reworked sands.Our core-seismic calibration debunked the conventional wisdom(groupthink)that basin-floor fans are composed of sandy turbidites in a sequence-stratigraphic framework.(22)Turbidite groupthink:A case study in illustrating how turbidite groupthink functions,without sound scientific methods,on the basis of published information on modern turbidity currents in Bute Inlet(fjord and estuary),British Columbia,Canada.This compendium is hybrid in composition between an atlas(with 108 figures)and a review article(with 348 references).The author admonishes scientists against deep-sea groupthink and provides a roadmap for future researchers by identifying potential topics for research involving density plumes,internal waves,tidal currents,tsunami waves,sediment deformation,and lowstand braid deltas.展开更多
Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restr...Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restricted to instrumental and historical data; the recognition of prehistoric earthquakes requires criteria to recognize seismites in the geological record.The areal distribution of seismites can sometimes be related to active faults since distances to the epicenter(for a given magnitude) tend to be related to the liquefaction effects of seismic shocks.The use of soft-sediment deformation structures for palaeoseismic studies has limitations,however.Hardly anything is known,for instance,about the effects that modern seismic events have on the sediments in most environments.Moreover,criteria for the recognition of seismites are still under discussion.The following characteristics seem,particularly in combination,the most reliable:(1) Soft-sediment deformation structures should occur in laterally continuous,preferably recurring horizons,separated by undeformed beds;(2) These deformation structures should be comparable with structures known to have been triggered by modern seismic activity;(3) The sedimentary basin should have experienced tectonic activity at the time when the deformations were formed; and(4) The intensity or abundance of the soft-sediment deformation structures in a presumed seismite should change laterally,depending on the distance to the epicenter.It turns out that all of these four criteria have important exceptions.(1) Soft-sediment deformation structures occurring over large lateral distances in a specific layer can be triggered also by other processes.Moreover,in environments with a low sedimentation rate,the time between successive earthquakes is often too short to allow accumulation of beds that remain undisturbed.Furthermore,total liquefaction of a sandy bed may result in the absence of deformation features.(2) No truly diagnostic soft-sediment deformation structures exist to prove seismic activity.Moreover,the final configuration of a soft-sediment deformation structure is independent of the type of trigger.(3) Seismites occur frequently in areas where seismic activity is low today.(4) The lateral changes in the intensity of soft-sediment deformation structures in seismites as a factor presumed to depend on the distances to the epicenter,pose a complicated problem.The 2012 Emilia earthquakes,for instance,affected sandy fluvial channels but not the fine-grained floodplains.It must thus be deduced that specific soft-sediment deformation structures cannot be used without additional evidence to identify seismites.In particular,the magnitude of seismic shocks and the recurrence time of main events(the most important features that allow recognition of seismites) seem to be sedimentological in nature:facies changes in space and time seem theparameters that most strongly control the occurrence,morphology,lateral extent and the vertical repetition of seismites.展开更多
A clastic dike containing unusually large clasts occurs in the Quaternary deposits that unconformably cover the Mesoproterozoic sediments in the Fangshan District,Beijing area,China.The material into which the dike in...A clastic dike containing unusually large clasts occurs in the Quaternary deposits that unconformably cover the Mesoproterozoic sediments in the Fangshan District,Beijing area,China.The material into which the dike intruded is also uncommon because it consists mainly of loess-type silts that were deposited by braided rivers.The intrusion of the dike is explained as the result of the expulsion of pore water into the coarse,gravel-containing layers of a braided river system.The large size of the clasts in the dike is explained by an exceptionally strong upwards directed flow which owed its high energy to a high hydrostatic pressure that had been built up because pore water could not gradually seep through the impermeable silt-sized material during ongoing burial.This uncommon dike is compared with a second example,in similar Quaternary sediments covering the Mesozoic rocks in the Huairou District.展开更多
基金the National Institute of Natural Hazards,Ministry of Emergency Management of China(ZDJ2019-21)the National Natural Science Foundation of China(Nos.41872227 and 41602221).
文摘The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.
基金granted by the doctor foundation of Henan Polytechnic University(NO:B2013-076)the National Nature Science Foundation of China(NO:4147208341440016)
文摘Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time: large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.
基金the Council of Scientific and Industrial Research, New Delhi, Government of India, for awarding him Shyama Prasad Mukherjee Fellowship [SPM-09/001(0328)/2020-EMRI]the Department of Science and Technology, Government of India, for the INSPIRE Fellowship [IF170168]
文摘The unequivocal identification of soft-sediment deformation structures(SSDS)is a significant attribute to constrain the effect of transient geological events in the spatio-temporal evolution of ancient sedimentary basins.This paper reports and discusses,for the first time,the occurrence of several cm-to dm-scale SSDS within sandstone successions of the Mesoproterozoic Kaimur Group(Vindhyan Supergroup),exposed at the Hanumandhara Hill of Chitrakoot-Satna border region,Madhya Pradesh State,India.The SSDS are confined to a deformed interval comprising seven individual sedimentary units of variable composition and texture,which are sandwiched between nearly horizontally undeformed sandstone beds.The SSDS consist of load structures(load casts,flame structures,pseudonodules and ball-and-pillow structures),contorted lamination,convolute lamination,boudins and pinch-and-swell structures,deformed cross-stratification,slump structures,clastic injections,fluid escape structures,and syn-sedimentary fractures/faults.The pre-sent study suggests that the formation of these SSDS is essentially related to a combination of processes(gravitational instability,liquefaction,fluidization,and fluid escape)predominantly induced by seismic shocks.In addition,the restricted occurrence of fractures/faults in these deformed layers emphasizes the passage of seismically-induced Rayleigh waves.Considering the observed types of SSDS,their lateral homo-geneity and geographic distribution along with the geodynamic framework of the Vindhyan Basin,the whole area can be tentatively attributed to having experienced moderate-to high-magnitude(M≥5)seismicity.The present study combined with earlier reports of seismically-induced SSDS,from other regionally disposed formations belonging to the Lower(e.g.,Kajrahat Limestone,Chopan Porcellanite,Koldaha Shale,Rohtas Limestone,and Glauconitic Sandstone of the Semri Group)and Upper(e.g.,Bhander Limestone of the Bhander Group)Vindhyan Supergroup,respectively,provides evidence for the constant regional-scale seismo-tectonic activity within the Paleo-Mesoproterozoic Vindhyan Basin.Importantly,this observation further suggests that the intracratonic basins can be active tectonically contrary to the earlier propositions.
文摘The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal environment that was ideal for recording earthquakes in the form of soft-sediment deformation structures (SSDS). Numerous examples occur in the upper part of the Wumishan Formation, along the Yongding River Valley. In addition, brittle structures include intrastratal fault and seismically cracked breccias. The soft-sediment deformation structures include liquefied features (diapirs, clastic dykes, convolute bedding), compressional deformation features (accordion folds, plate-spine breccias, mound-and-sag structures), and extensional plastic features (loop-bedding). Based on the regional geological setting and previous research, movements along the main axial fault of the Yan-Liao aulacogen are considered as the triggers for earthquakes since the Early Mesoproterozoic. The number and distribution of the SSDS suggest the major earthquake frequency in the Wumishan Formation of 20 to 32 thousand years.
基金financially supported by the National Natural Science Foundation of China(41772116)。
文摘The Nihewan Basin is a rift basin at the junction of northern Shanxi Province and northwestern Hebei Province in north China.The basin is known for its rich paleontological fossils and ancient human remains.There are also abundant soft-sediment deformation structures(SSDS)in the thick lacustrine sediments.Previously,most SSDS have been interpreted as ice-edge features or ignored entirely.Recently,the authors have carried out several field surveys in the Nihewan Basin and found that many SSDS are sandwiched between normal lacustrine strata at multiple sections.In the excavation pit at the 10th Locality of Maliang Site(ML10),10 horizontal SSDS layers and two vertically developed geological features have been identified.Based on genesis analysis and related criteria,these features are divided into two categories:cryoturbation-triggered SSDS and earthquake-triggered SSDS.Among them,a special type of ancient ice-wedge pseudomorph(SSDS-8)of ML10 is recognized in the basin for the first time.The other 9 horizontal SSDS are mainly caused by earthquake-triggered liquefaction and slumping.They can be further divided into 14 seismic event layers.These findings indicate that the tectonic activity in the Nihewan Basin is very strong and frequent,and there were cold periods in the geological history of the basin.At the same time,the SSDS with distinct morphological characteristics and stable horizontal distribution in the basin can be used as an important indicator of stratigraphic correlation.
基金supported by National Natural Science Foundation of China (Grant Nos. 41172125, 40972090, 40802030, 40672143 and 40472107)National Basic Research Program of China (Grant Nos. 2012CB214804,2005CB422107 and G1999043305)+3 种基金Investigation and Evaluation on Strategic Region of National Oil and Gas Resource (Grant No. 2009GYXQ0205)Doctoral Fund of Ministry of Education of China (Grant No.200804250001)National Key Scientific Project (Grant No.2011ZX05002-003-001HZ)Northwest Oilfield Company of SINOPEC has given full support with fundamental geologic data
文摘The salt beds of the Middle-Lower Cambrian are widespread in the middle-west parts of the Central Uplift and adjacent areas, the Tarim Basin. This paper presents the results of seismic interpretation and drilling data analysis, which discovered that the salt beds were formed in an old geologic age, deeply buried, with relatively small scaled flowing and gathering and uneven distribution. As the regional detachment layers, the salt sequences considerably control the structural deformation of the up-salt Paleozoic, forming a series of hydrocarbon traps. In due course, the salt beds of the Middle-Lower Cambrian provide excellent cap rocks and trap conditions; thus the value of exploring hydrocabon reservoir in the target strata of the sub-salt Sinian- Cambrian is greatly increased. Research has shown that the salt-related structures of the Middle-Lower Cambrian in the area mainly exist in the form of salt pillow, salt roller, up-salt anticline, salt diapir, assemblage of the salt arch and up-salt fault-block, assemblage of basement fault and salt anticline, assemblage of the basement fault-block and salt dome, assemblage of salt detachment and fault-related fold, and assemblage of basement fault-block, salt arch and up-salt imbricated thrusts. The evolution and deformation mechanisms of the salt-related structures are controlled largely by basement faulting, compressional shortening, plastic flowing and gathering, superstratum gravitation, and up-salt faulting and detaching. They are distributed in rows or belts along basement faults or fault block belts.
基金supported by the“Natural Science Foundation of Heilongjiang Province(No.JJ2016ZR0573)”“Youth Foundation of Northeast Petroleum University(No.NEPUBS201503)”+2 种基金“Northeast Petroleum University Scientific Research Start-up Fund”“Shandong Provincial Key Laboratory of Depositional Mineralization and Mineral Foundation(No.DMSMZO17009)”“Natural Science Foundation of Shandong Province(No.ZR2016DB15)”.
文摘An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault,Second Songhua River Fault and Fuyu North Fault which lies northwest of TanchengLujiang Fault(Tan-Lu Fault).The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter,caused serious disasters to the local surroundings.The visible liquefied structures include sand volcanoes,liquefied sand mounds,sand dikes and sand sills.Sand volcanoes can be divided into sand volcano with a crater,sand volcano without a crater and water volcano(no sand).Other soft-sediment deformation structures(SSDS)induced by the earthquake include deformation lamination,load and flame structures,deformation folds,dish structures,convolute bedding and water-escape structures.The formation process of the sand volcanoes comprises three stages:(1)building up excess pore-fluid pressure in the liquefied layer,(2)cracking of the low-permeable overlying layer,and(3)mixture of sand-water venting out of the ground surface.During the upward movement,the liquefied sand is injected into the low-permeable layer to form sand veins,sand sills and various types of deformation structures.Vertical distribution of seismic liquefaction structure can be divided into four zones:the thoroughly liquefied zone,the lower liquefied zone with SSDS,the upper liquefied zone with SSDS,and the ground surface liquefied zone.The liquefaction occurred at a burial depth of 2–5 m,and the thickness of liquefied sand is 2 m.NE-SW(35°–215°)trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault(Fuyu/Songyuan-Zhaodong Fault)to reactivate.The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disasterprone areas.Meanwhile it provides abundant basic material for studying earthquake-induced SSDS in both ancient and modern sediments.The research is obviously of great significance to reveal that the northern Tan-Lu Fault has entered a stage of active seismic activity since the twenty-first century.
文摘In capturing a snapshot of 150 years(1872-2022)of research on deep-water processes,deposits,settings,triggers,and deformation,the following 22 topics are selected:(1)H.M.S.Challenger expedition(1872-1876):The discovering of the“Challenger Deep”by the H.M.S.Challenger in the Mariana Trench has been the single most important achievement in deep-water research.(2)Five pioneers amid 50 notable contributors:R.A.Bagnold,J.E.Sanders,G.D.Klein,F.P.Shepard,and C.D.Hollister.(3)Mass transport:Mass-transport deposits(MTD)are the most important deep-water facies in terms of volume,geohazards,and petroleum reservoirs.(4)Gravity flows:There are six basic types,namely(a)hyperpycnal flows,(b)turbidity currents,(c)debris flows,(d)liquefied/fluidized flows,(e)grain flows,and(f)thermohaline contour currents.Sandy debrites are the most important petroleum reservoir facies.Despite their popularity,turbidites are not an important reservoir facies.(5)Kelvin-Helmholtz(KH)waves:Turbidites,related to KH waves,with internal hiatus are not qualified to function as predictive facies models;nor are they fit for stratigraphic correlations.(6)High-density turbidity currents(HDTC):Misclassification of density-stratified gravity flows with laminar debris flows and turbulent turbidity currents as HDTC is flawed.Experimental generation of density-stratified gravity flows in flume studies has debunked the concept of HDTC.(7)Classification of turbidites:Contrary to the popular groupthink,turbidites are exclusive deposits of turbidity currents.(8)Bottom currents:The four basic types of deep-marine bottom currents are:(a)thermohaline-induced geotropic contour currents,(b)wind-driven bottom currents,(c)tide-driven bottom currents(mostly in submarine canyons),and(d)internal wave/tide-driven baroclinic currents.(9)Classification of contourites:Contrary to the popular groupthink,contourites are the exclusive deposits of thermohaline-induced geotropic contour currents.(10)Tidal currents in submarine canyons:Their velocity measurements have been the single most important achievement in deep-water process sedimentology.(11)Modern and ancient systems:There is a dichotomy between rare observations of turbidity currents in modern settings and overwhelming cases of interpretations of ancient turbidites in outcrops and cores.The reason is that turbidity currents are truly rare in nature,but the omnipotent presence of turbidites in the ancient rock record is the manifestation of groupthink induced by the turbidite facies model(i.e.,the Bouma Sequence).(12)Internal waves and tides:Despite their ubiquitous documentation in modern oceans,their ancient counterparts in outcrops are extremely rare.This is another dichotomy.(13)Hybrid flows:They are commonly developed by intersecting of down-slope gravity flows with along-slope contour currents.However,they are often misapplied to down-slope flow transformation of gravity flows.(14)Density(sediment)plumes:Deflected sediment plumes by wind forcing are common.Despite their importance in provenance studies,they are not adequately studied.(15)Hyperpycnal flows:They occur near the shoreline,next to the plunge point;but are of no relevance in deep-water environments.However,their importance in deep-marine settings is overhyped in recent literature.(16)Omission of erosional contact and internal hiatus:In order to promote genetic facies models that must not contain internal hiatuses,some researchers selectively omit internal hiatuses observed by the original authors.(17)Triggers of sediment failures:There are 22 types,but short-term triggers,such as earthquakes and meteorite impacts are more important than the conventional long-term trigger known as Eustasy.(18)Tsunami waves:Despite their sedimentologic importance,there are no reliable criteria for recognizing tsunami deposits in the ancient rock record.(19)Soft-Sediment Deformation Structures(SSDS):Although most SSDS are routinely interpreted as seismites,not all SSDS are caused by earthquakes.There are 10 other mechanisms,such as sediment loading,which can trigger liquefaction that can develop SSDS.(20)The Jackfork Group,Pennsylvanian,Ouachita Mountains,USA:Our reinterpretation of this classic North American flysch turbidites as MTD and bottomcurrent reworked sands has resulted in the longest academic debate with 42 printed pages in the AAPG Bulletin history since its founding in 1917.(21)Basin-floor fan model,Tertiary,North Sea:Our examination of nearly 12,000 ft(3658 m)of conventional core from Paleogene and Cretaceous deep-water sandstone reservoirs cored in 50 wells in 10 different areas or fields in the North Sea and Norwegian Sea reveals that these reservoirs are predominantly composed of MTDs,mainly sandy slumps and sandy debrites,and bottom-current reworked sands.Our core-seismic calibration debunked the conventional wisdom(groupthink)that basin-floor fans are composed of sandy turbidites in a sequence-stratigraphic framework.(22)Turbidite groupthink:A case study in illustrating how turbidite groupthink functions,without sound scientific methods,on the basis of published information on modern turbidity currents in Bute Inlet(fjord and estuary),British Columbia,Canada.This compendium is hybrid in composition between an atlas(with 108 figures)and a review article(with 348 references).The author admonishes scientists against deep-sea groupthink and provides a roadmap for future researchers by identifying potential topics for research involving density plumes,internal waves,tidal currents,tsunami waves,sediment deformation,and lowstand braid deltas.
文摘Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restricted to instrumental and historical data; the recognition of prehistoric earthquakes requires criteria to recognize seismites in the geological record.The areal distribution of seismites can sometimes be related to active faults since distances to the epicenter(for a given magnitude) tend to be related to the liquefaction effects of seismic shocks.The use of soft-sediment deformation structures for palaeoseismic studies has limitations,however.Hardly anything is known,for instance,about the effects that modern seismic events have on the sediments in most environments.Moreover,criteria for the recognition of seismites are still under discussion.The following characteristics seem,particularly in combination,the most reliable:(1) Soft-sediment deformation structures should occur in laterally continuous,preferably recurring horizons,separated by undeformed beds;(2) These deformation structures should be comparable with structures known to have been triggered by modern seismic activity;(3) The sedimentary basin should have experienced tectonic activity at the time when the deformations were formed; and(4) The intensity or abundance of the soft-sediment deformation structures in a presumed seismite should change laterally,depending on the distance to the epicenter.It turns out that all of these four criteria have important exceptions.(1) Soft-sediment deformation structures occurring over large lateral distances in a specific layer can be triggered also by other processes.Moreover,in environments with a low sedimentation rate,the time between successive earthquakes is often too short to allow accumulation of beds that remain undisturbed.Furthermore,total liquefaction of a sandy bed may result in the absence of deformation features.(2) No truly diagnostic soft-sediment deformation structures exist to prove seismic activity.Moreover,the final configuration of a soft-sediment deformation structure is independent of the type of trigger.(3) Seismites occur frequently in areas where seismic activity is low today.(4) The lateral changes in the intensity of soft-sediment deformation structures in seismites as a factor presumed to depend on the distances to the epicenter,pose a complicated problem.The 2012 Emilia earthquakes,for instance,affected sandy fluvial channels but not the fine-grained floodplains.It must thus be deduced that specific soft-sediment deformation structures cannot be used without additional evidence to identify seismites.In particular,the magnitude of seismic shocks and the recurrence time of main events(the most important features that allow recognition of seismites) seem to be sedimentological in nature:facies changes in space and time seem theparameters that most strongly control the occurrence,morphology,lateral extent and the vertical repetition of seismites.
文摘A clastic dike containing unusually large clasts occurs in the Quaternary deposits that unconformably cover the Mesoproterozoic sediments in the Fangshan District,Beijing area,China.The material into which the dike intruded is also uncommon because it consists mainly of loess-type silts that were deposited by braided rivers.The intrusion of the dike is explained as the result of the expulsion of pore water into the coarse,gravel-containing layers of a braided river system.The large size of the clasts in the dike is explained by an exceptionally strong upwards directed flow which owed its high energy to a high hydrostatic pressure that had been built up because pore water could not gradually seep through the impermeable silt-sized material during ongoing burial.This uncommon dike is compared with a second example,in similar Quaternary sediments covering the Mesozoic rocks in the Huairou District.