Late Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya

Bulletin of geosciences

Steemans P¹  Paris F¹  LeHerisse A¹ 

关键词: northern Gondwana;    Chad;    Libya;    Ordovician-Silurian boundary;    acritarchs;    chitinozoans;    spores;    biostratigraphy;    palaeoenvironment;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

Wellpreservedassemblagesofcryptospores,chitinozoans,acritarchs,leiospheres,tasmanitids,coloniesofGloeocapsomorpha,scolecodontsandeurypteridfragmentsfrom23coresamplesoftheMoussegoudacoreholeintheErdiBasin,northernChad,andfromtwosamplesfromwellKW-2inKufraBasin,SouthEastLibyaareinvestigated.ThesepalynomorphswererecoveredfromthesouthernmostNorthAfricanmarinedepositsofLateOrdovicianandpossiblyearlySilurianage.ThepalaeoenvironmentevolvesfromlateHirnantianglacio-marinediamictitestosilt-dominatedsequencessuggestingamarginalmarineenvironmentofpossiblylatestHirnantiantoearliestRhuddanianage(post-elongata-pre-fragilischitinozoanassemblages).TherecoveredpalynomorphassemblagesarecomparedandcorrelatedwithcontemporaneousassemblagesrecordedinothernorthernGondwanalocalities(Mauritania,MoroccoAlgeria,Libya,Africa,SaudiArabia,Jordan),andinSouthAfrica,inordertoevaluatepossibleeffectsoftheicecapmeltingonpalynomorphassemblagesandsedimentation.OurgoalisalsotoimprovetheregionalbiostratigraphyacrosstheOrdovician-Silurianboundary.Thecompositionoftherecoveredpalynomorphassemblages,withmixedterrestrialandmarinemicroflora,suggeststhatthetopmostOrdovicianorearliestSilurianinnorthernChadandsoutheasternLibya,reflectsnearshoreconditions,withobviousfreshwaterinfluences.ThelackofblackshaleorgreyshaleintheuppermostOrdovicianandof“hotshale”inthelowerSilurianintheseareas,andtheirreplacementbysiltstones,areprobablyrelatedtoanisostaticreadjustmentthatrapidlystarvedthemarinesedimentationintheareaspreviouslyoverlainbyathickicecoverduringtheclimaxoftheHirnantianglaciation.TasmanitestzadiensisLeHerissesp.nov.andEuconochitinamoussegoudaensisParissp.nov.,twonewpalynomorphsofbiostratigraphicalinterestaredescribedandillustrated.

【 授权许可】

Unknown