Fluvial deposits from the Middle Triassic Youfangzhuang Formation in Henan Province, China contain a low-diversity trace fossils. Vertical dwelling burrows of opportunists dominate in active channel, whereas horizonta...Fluvial deposits from the Middle Triassic Youfangzhuang Formation in Henan Province, China contain a low-diversity trace fossils. Vertical dwelling burrows of opportunists dominate in active channel, whereas horizontal deposit-feeding, grazing, and vertical dwelling burrows occur in overbank deposits. Seven recurrent ichnofabrics were distingushed. The Palaeophycus tubularis ichnofabric pre- serves below scour interface between two fluvial cycles. The Skolithos linearis ichnofabric forms in middle to high-energy, soft substrates in the middle and upper parts of active channel deposits under semi-arid climate. The Skolithos linearis-Planolites montanus ichnofabric occurs in the sediments just a little above the Skolithos linearis ichnofabric and is formed in middle-energy, soft substrates in the up- per part of active channel deposits. The Planolites montanus ichnofabric is mostly preserved in associa- tion with medium- to thick-bedded brown-red silty mudstones or siltstones in low-energy, perennial muddy bottom ponds in overbank settings. The Taenidium barretti ichnofabric is interpreted as peri- odically exposed ephemeral ponds or low-energy distal floodplain. The Skolithos isp. ichnofabric com- monly occurs in middle to high-energy firm ground of proximal foodplain or crevasse-splay deposits. The root trace iehnofabric occurs in the crevasse splay deposits. The presence of thin palaeosols and the abundance of calcretization in mudstones indicate a seasonal climate ranging from humid to semi-arid, with high temperature, rainfall, and well-defined dry and wet seasons.展开更多
The Chhasra Formation(CF)of Kutch Basin exemplifies a typical mixed siliciclastic-carbonate system with alternations of biostromal carbonate and fine-grained siliciclastic beds.The CF is subdivided into two members:th...The Chhasra Formation(CF)of Kutch Basin exemplifies a typical mixed siliciclastic-carbonate system with alternations of biostromal carbonate and fine-grained siliciclastic beds.The CF is subdivided into two members:the lower Claystone(CM)and the upper Siltstone(SM)member.Three CM outcrops(P1-P3)comprising buried palaeosols that formed under a specific environmental set-up involving imperfectly to poorly drained conditions,are exposed along the Berwali River.The biostromal carbonate beds,alternating with the palaeosols,contain invertebrate bioclasts(bivalves,gastropods,echinoids,etc.)and are characterized by a paucispecific firmground Thalassinoides ichnofabric.At section P1,below the contact between the underlying palaeosol and overlying carbonate,Thalassinoides transforms into firmground Gyrolithes inside the palaeosol forming a compound ichnotaxon.The palaeosol intervals of sections P1 and P2 consist of a Vondrichnus-Termitichnus-root trace ichnofabric defining the Termitichnus ichnofacies.At section P3,lenses of fully bioturbated siltstones with a monospecific firmground Thalassinoides ichnofabric can be observed within an overall silty palaeosol horizon,thereby,locally cross-cutting the pedogenic features.The ichnofabrics of section P3 indicate polyphase pedogenesis with three stages:(1)initial stage:pedogenesis in siltstone of undefined depositional affinity which was obscured by pedogenic processes,(2)transient stage:recurring marine incursions and colonization by crustaceans within the lens-shaped palaeotopographic depressions overprinting the palaeosol,and(3)final stage:subaerial exposure and another preserved phase of pedogenesis.The CM shows an apparent low-order T-R(transgressive-regressive)cyclicity within a 3rd-order TST(transgressive systems tract)that is supported by pedogenic intensity,ichnofabrics,and reciprocal sedimentation near the Miocene basin margin,though the cyclicity can be the result of both autogenic and/or lowerorder allogenic changes.展开更多
Integrating the ichnologic,taphonomic,and sedimentologic data enhances the accuracy of palaeoenvironmental interpretations.The integrated analysis of the Chattian-age Coral Limestone Member within the Maniyara Fort Fo...Integrating the ichnologic,taphonomic,and sedimentologic data enhances the accuracy of palaeoenvironmental interpretations.The integrated analysis of the Chattian-age Coral Limestone Member within the Maniyara Fort Formation in Kutch Basin focuses on understanding the palaeogeographic architecture of microfacies association and the influencing factors determining the same on a typical Late Oligocene carbonate ramp.Through distinct petrographic examination,six distinct microfacies representing outer ramp(MF1 and MF2),middle ramp(MF3,MF4,and MF5),and inner ramp(MF6)depositional settings were identified.The Member,characterised primarily by multiple carbonate coquina intervals,was further classified based on taphonomical and ichnological characteristics.Four taphofacies(TF1,TF2,TF3,and TF4)and five ichnofabrics were identified.The outer ramp exhibits massive-appearing intensely to completely bioturbated(BI 5-6)marly mudstone-wackestone lithofacies with erosional contacts.The middle ramp displays oligotrophic conditions characterised by swaley cross-stratified bioclastic packstone-rudstone beds showing an upward intensifying moderate to intense bioturbation(BI 3-5).The storm-influenced inner ramp features the crudely swaley cross-stratified rudstone shell beds and patchy coral reefs with intense bioturbation(BI 5).Intermittent non-depositional and bioerosional short-duration episodes were observed at the top of skeletal concentrations.The integrated findings mentioned above exhibit coherence and offer valuable insights into the development of carbonate ramps.Our study offers insight into the aggrading and prograding shoal deposits within the carbonate ramp settings of a Chattian tropical sea.It highlights the complex interaction of environmental factors during this period within a high-resolution sequence-stratigraphic framework,extending up to the 5th-order,reported for the first time.This study deepens our comprehension of Oligocene carbonate buildups on a global scale—a research that has received lesser recognition compared to Eocene or Miocene carbonates.展开更多
In the Bay of Bengal,the Andaman and Nicobar Islands represent part of the Burma-Sunda-Java subduction complex.The Islands are composed of sediments ranging in age from Jurassic to Recent,represented by ophiolites,fly...In the Bay of Bengal,the Andaman and Nicobar Islands represent part of the Burma-Sunda-Java subduction complex.The Islands are composed of sediments ranging in age from Jurassic to Recent,represented by ophiolites,flysch sediments,along with deep marine sediments scraped off from the subducting plate.The stratigraphic succession that overlies meta-sedimentary and ophiolite suites consists of turbidite and non-turbidite sequences,along with thick-bedded nannofossil chalks.The present study describes ichnofabrics of chalks from the Inglis Formation(Early to Middle Miocene).These chalks are highly to moderately bioturbated and comprise several levels of ferruginised layers as weak discontinuity surfaces.The studied section shows the recurring occurrence of ichnotaxa belonging to Asterosoma,Chondrites,Cladichnus,Ophiomorpha,Palaeophycus,Planolites,Taenidium,Thalassinoides,and Zoophycus.Sediments are represented by Bioturbation indices varying between BI-2 to BI-5,represented by(a)light coloured trace fossils in dark sediment(LID ichnofabric)and(b)dark coloured trace fossils in light sediment(DIL ichnofabric).Ichnofabric analysis suggests multiple colonization,complex tiering,and multilayer tiering.The LID ichnofabric exposed at Kalapathar reveals three tiers,a diverse shallow tier and a moderately low diverse middle and deep tiers.At the Lacam Point Section,in contrast,the LID ichnofabric is represented by condensation of the tiers and the absence of shallow tiers.The DIL ichnofabric at the Kalapathar Section seems to be more expanded and is represented by four tiers with extensive bioturbation.Ichnofabric analysis supports deposition of the chalk sediments in a lower bathyal paleoenvironment and suggests that organic matter,pore water,and bottom-water oxygenation were the main controlling factors.Thus,the ichnofabric analysis of the EarlyMiddle Miocene Inglis Formation gives first-hand information regarding the poorly known chalk facies of the Andaman and Nicobar Islands pre-Bengal fan stage of the Indian plate.展开更多
The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come fr...The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.展开更多
The 14^（th） International Ichnofabric Workshop was held successfully in Taipei, China from April 29 thto May 2^（nd）. From the oral presentations, posters, intra-and post-workshop field trips, and workshop discussi...The 14^（th） International Ichnofabric Workshop was held successfully in Taipei, China from April 29 thto May 2^（nd）. From the oral presentations, posters, intra-and post-workshop field trips, and workshop discussions, a few promising aspects of ichnological study can be outlined：（1） Ichnotaxonomy is, and will be the major endeavour of ichnologists, supplying important behavioural information for palaeontological studies, and also providing reasonable, objective, and convenient taxonomical framework for further sedimentological and palaeoecological studies;（2） Ichnofabric analysis is widely applied to in-depth sedimentological, palaeoclimatical, and petroleum exploration studies, offering a wealth of biological information that cannot be properly obtained from traditional sedimentological and geochemical analyses;（3） Study of trace fossils in the context of evolutionary palaeoecology sheds light on some intriguing issues of the biological responses during certain critical periods in Earth＇s history;（4）Work on combining geomicrobiology and ichnology is under way;（5） Quantitative morphological characterization has become increasingly useful in grasping the finer ingredients of functional morphology.展开更多
基金supported by the National Natural Science Foundation of China (No. 41072003)the Fostering Foundation of Henan Polytechnic University for the Excellent Ph. D Dissertation (No. 2011011001)
文摘Fluvial deposits from the Middle Triassic Youfangzhuang Formation in Henan Province, China contain a low-diversity trace fossils. Vertical dwelling burrows of opportunists dominate in active channel, whereas horizontal deposit-feeding, grazing, and vertical dwelling burrows occur in overbank deposits. Seven recurrent ichnofabrics were distingushed. The Palaeophycus tubularis ichnofabric pre- serves below scour interface between two fluvial cycles. The Skolithos linearis ichnofabric forms in middle to high-energy, soft substrates in the middle and upper parts of active channel deposits under semi-arid climate. The Skolithos linearis-Planolites montanus ichnofabric occurs in the sediments just a little above the Skolithos linearis ichnofabric and is formed in middle-energy, soft substrates in the up- per part of active channel deposits. The Planolites montanus ichnofabric is mostly preserved in associa- tion with medium- to thick-bedded brown-red silty mudstones or siltstones in low-energy, perennial muddy bottom ponds in overbank settings. The Taenidium barretti ichnofabric is interpreted as peri- odically exposed ephemeral ponds or low-energy distal floodplain. The Skolithos isp. ichnofabric com- monly occurs in middle to high-energy firm ground of proximal foodplain or crevasse-splay deposits. The root trace iehnofabric occurs in the crevasse splay deposits. The presence of thin palaeosols and the abundance of calcretization in mudstones indicate a seasonal climate ranging from humid to semi-arid, with high temperature, rainfall, and well-defined dry and wet seasons.
基金the following funding agencies for the research grants:Science and Engineering Research Board (SERB)Government ofIndia (grant#CRG/2018/000259 to SDG)+2 种基金Industrial Research and Consultancy Centre (IRCC)IIT Bombay (seed grant#RD/0517-IRCCSH0-035 to SDG)Council of Scientific&Industrial Research (CSIR) (doctoral scholarship for AS)。
文摘The Chhasra Formation(CF)of Kutch Basin exemplifies a typical mixed siliciclastic-carbonate system with alternations of biostromal carbonate and fine-grained siliciclastic beds.The CF is subdivided into two members:the lower Claystone(CM)and the upper Siltstone(SM)member.Three CM outcrops(P1-P3)comprising buried palaeosols that formed under a specific environmental set-up involving imperfectly to poorly drained conditions,are exposed along the Berwali River.The biostromal carbonate beds,alternating with the palaeosols,contain invertebrate bioclasts(bivalves,gastropods,echinoids,etc.)and are characterized by a paucispecific firmground Thalassinoides ichnofabric.At section P1,below the contact between the underlying palaeosol and overlying carbonate,Thalassinoides transforms into firmground Gyrolithes inside the palaeosol forming a compound ichnotaxon.The palaeosol intervals of sections P1 and P2 consist of a Vondrichnus-Termitichnus-root trace ichnofabric defining the Termitichnus ichnofacies.At section P3,lenses of fully bioturbated siltstones with a monospecific firmground Thalassinoides ichnofabric can be observed within an overall silty palaeosol horizon,thereby,locally cross-cutting the pedogenic features.The ichnofabrics of section P3 indicate polyphase pedogenesis with three stages:(1)initial stage:pedogenesis in siltstone of undefined depositional affinity which was obscured by pedogenic processes,(2)transient stage:recurring marine incursions and colonization by crustaceans within the lens-shaped palaeotopographic depressions overprinting the palaeosol,and(3)final stage:subaerial exposure and another preserved phase of pedogenesis.The CM shows an apparent low-order T-R(transgressive-regressive)cyclicity within a 3rd-order TST(transgressive systems tract)that is supported by pedogenic intensity,ichnofabrics,and reciprocal sedimentation near the Miocene basin margin,though the cyclicity can be the result of both autogenic and/or lowerorder allogenic changes.
基金supported by the Science and Engineering Research Board(SERB)Government of India(Grant No.CRG/2018/000259 to SDG)+3 种基金Industrial Research and Consultancy Centre(IRCC)IIT Bombay(Seed Grant No.RD/0517-IRCCSH0-035 to SDG)Council of Scientific and Industrial Research(CSIR)(Dr.SP Mukherjee Fellowship No.SPM09/0087(13946)/2022-EMR-I to KPDoctoral Fellowship No.09/0087(0993)/2019-EMR-I to RD)。
文摘Integrating the ichnologic,taphonomic,and sedimentologic data enhances the accuracy of palaeoenvironmental interpretations.The integrated analysis of the Chattian-age Coral Limestone Member within the Maniyara Fort Formation in Kutch Basin focuses on understanding the palaeogeographic architecture of microfacies association and the influencing factors determining the same on a typical Late Oligocene carbonate ramp.Through distinct petrographic examination,six distinct microfacies representing outer ramp(MF1 and MF2),middle ramp(MF3,MF4,and MF5),and inner ramp(MF6)depositional settings were identified.The Member,characterised primarily by multiple carbonate coquina intervals,was further classified based on taphonomical and ichnological characteristics.Four taphofacies(TF1,TF2,TF3,and TF4)and five ichnofabrics were identified.The outer ramp exhibits massive-appearing intensely to completely bioturbated(BI 5-6)marly mudstone-wackestone lithofacies with erosional contacts.The middle ramp displays oligotrophic conditions characterised by swaley cross-stratified bioclastic packstone-rudstone beds showing an upward intensifying moderate to intense bioturbation(BI 3-5).The storm-influenced inner ramp features the crudely swaley cross-stratified rudstone shell beds and patchy coral reefs with intense bioturbation(BI 5).Intermittent non-depositional and bioerosional short-duration episodes were observed at the top of skeletal concentrations.The integrated findings mentioned above exhibit coherence and offer valuable insights into the development of carbonate ramps.Our study offers insight into the aggrading and prograding shoal deposits within the carbonate ramp settings of a Chattian tropical sea.It highlights the complex interaction of environmental factors during this period within a high-resolution sequence-stratigraphic framework,extending up to the 5th-order,reported for the first time.This study deepens our comprehension of Oligocene carbonate buildups on a global scale—a research that has received lesser recognition compared to Eocene or Miocene carbonates.
文摘In the Bay of Bengal,the Andaman and Nicobar Islands represent part of the Burma-Sunda-Java subduction complex.The Islands are composed of sediments ranging in age from Jurassic to Recent,represented by ophiolites,flysch sediments,along with deep marine sediments scraped off from the subducting plate.The stratigraphic succession that overlies meta-sedimentary and ophiolite suites consists of turbidite and non-turbidite sequences,along with thick-bedded nannofossil chalks.The present study describes ichnofabrics of chalks from the Inglis Formation(Early to Middle Miocene).These chalks are highly to moderately bioturbated and comprise several levels of ferruginised layers as weak discontinuity surfaces.The studied section shows the recurring occurrence of ichnotaxa belonging to Asterosoma,Chondrites,Cladichnus,Ophiomorpha,Palaeophycus,Planolites,Taenidium,Thalassinoides,and Zoophycus.Sediments are represented by Bioturbation indices varying between BI-2 to BI-5,represented by(a)light coloured trace fossils in dark sediment(LID ichnofabric)and(b)dark coloured trace fossils in light sediment(DIL ichnofabric).Ichnofabric analysis suggests multiple colonization,complex tiering,and multilayer tiering.The LID ichnofabric exposed at Kalapathar reveals three tiers,a diverse shallow tier and a moderately low diverse middle and deep tiers.At the Lacam Point Section,in contrast,the LID ichnofabric is represented by condensation of the tiers and the absence of shallow tiers.The DIL ichnofabric at the Kalapathar Section seems to be more expanded and is represented by four tiers with extensive bioturbation.Ichnofabric analysis supports deposition of the chalk sediments in a lower bathyal paleoenvironment and suggests that organic matter,pore water,and bottom-water oxygenation were the main controlling factors.Thus,the ichnofabric analysis of the EarlyMiddle Miocene Inglis Formation gives first-hand information regarding the poorly known chalk facies of the Andaman and Nicobar Islands pre-Bengal fan stage of the Indian plate.
基金the Sao Paulo Research Foundation(FAPESP)for supporting and funding this work(grant 2015/17632-5)The Brazilian National Council for Scientific and Technological Development(CNPq)is also thanked for the Ph.D.grant provided to DLN(140807/2017-9)+3 种基金the post-doctoral fellowship grant to DS(159548/2018-7)the research grants to AB(310734/2020-7)RGN(310377/2019-6)FSBL(307951/2018-9,303977/2021-3).
文摘The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.
基金supported by the National Natural Science Foundation of China [grant numbers 41290260, 41472001]
文摘The 14^（th） International Ichnofabric Workshop was held successfully in Taipei, China from April 29 thto May 2^（nd）. From the oral presentations, posters, intra-and post-workshop field trips, and workshop discussions, a few promising aspects of ichnological study can be outlined：（1） Ichnotaxonomy is, and will be the major endeavour of ichnologists, supplying important behavioural information for palaeontological studies, and also providing reasonable, objective, and convenient taxonomical framework for further sedimentological and palaeoecological studies;（2） Ichnofabric analysis is widely applied to in-depth sedimentological, palaeoclimatical, and petroleum exploration studies, offering a wealth of biological information that cannot be properly obtained from traditional sedimentological and geochemical analyses;（3） Study of trace fossils in the context of evolutionary palaeoecology sheds light on some intriguing issues of the biological responses during certain critical periods in Earth＇s history;（4）Work on combining geomicrobiology and ichnology is under way;（5） Quantitative morphological characterization has become increasingly useful in grasping the finer ingredients of functional morphology.
