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
During an expedition to a seamount at Caroline Plate in the tropical Western Pacific,a new species of Tritonia was sampled from the upper bathyal zone at depth of 970-1262 m.This new species,Tritonia iocasica sp.nov.,...During an expedition to a seamount at Caroline Plate in the tropical Western Pacific,a new species of Tritonia was sampled from the upper bathyal zone at depth of 970-1262 m.This new species,Tritonia iocasica sp.nov.,represents the first tritoniid nudibranch known to feed on octocoral of the family Melithaeidae.The species is up to 120 mm in length,pinkish in color;with the rhinophoral sheath divided into several petaliform extensions;veil with,about 18 elongate digitiform processes;notal margin with17-19 pairs of secondary gills;anus located below the 5th and 6th secondary gills,and the genitalia below the 3rd secondary gill on the right side of the body.Based on these external features,T.iocasica sp.nov.can be dearly distinguished from all previously described members of the genus.Phylogenetic analyses of two mitochondrial(COI,16 S rRNA)and a nuclear(H3)genes using Bayesian inference,maximum likelihood,and species delimitation analysis also support the separation of T.iocasica sp.nov.from its congeners.展开更多
It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ...It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ichnogenera are mostly of typical deep-water ones and belong to the Nereites ichnofacies A detailed study of morphology and behaviour of the trace fossils indicates that the Shujiaba Formation was deposited in a bathyal-abyssal environment.展开更多
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 Science&Technology Basic Resources Investigation Program of China(No.2017FY100804)the Key Program of National Natural Science Foundation of China(No.41930533)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)the Major Program of National Natural Science Foundation of China(No.42090044)the Senior User Project of R/V Kexue(No.Kexue2020G02)。
文摘During an expedition to a seamount at Caroline Plate in the tropical Western Pacific,a new species of Tritonia was sampled from the upper bathyal zone at depth of 970-1262 m.This new species,Tritonia iocasica sp.nov.,represents the first tritoniid nudibranch known to feed on octocoral of the family Melithaeidae.The species is up to 120 mm in length,pinkish in color;with the rhinophoral sheath divided into several petaliform extensions;veil with,about 18 elongate digitiform processes;notal margin with17-19 pairs of secondary gills;anus located below the 5th and 6th secondary gills,and the genitalia below the 3rd secondary gill on the right side of the body.Based on these external features,T.iocasica sp.nov.can be dearly distinguished from all previously described members of the genus.Phylogenetic analyses of two mitochondrial(COI,16 S rRNA)and a nuclear(H3)genes using Bayesian inference,maximum likelihood,and species delimitation analysis also support the separation of T.iocasica sp.nov.from its congeners.
基金Project supported by the National Natural Science Foundation of China.
文摘It is beheved that the Shujiaba Formation belongs to a series of thick turbidites. 20 ichnogenera have been found in the formation, of which 14 genera were found in the Devonian System of China for the first time The ichnogenera are mostly of typical deep-water ones and belong to the Nereites ichnofacies A detailed study of morphology and behaviour of the trace fossils indicates that the Shujiaba Formation was deposited in a bathyal-abyssal environment.
