Castle Conglomerate Unit of the Upper Silesian Basin (Czech Republic and Poland): a record of the onset of Late Mississippian C2 glaciation?

Bulletin of geosciences

Jirásek J¹  Sedláčková L¹  Sivek M¹  Martínek K¹  Jureczka J¹ 

关键词: Ostrava Formation;    Upper Silesian Basin;    Mississippian;    Carboniferous;    sedimentology;    glaciation;    paleovalley;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

TheCastleConglomerateUnitinthePorubaMember(EarlyNamurian,Mississippian)isalithosomecomposedofcoarse-grainedsandstonesandconglomerates.Itsthickness,lithologyandextensiveareamakeituniqueintheparalicsequenceoftheOstravaFormationoftheUpperSilesianBasin.Theunitwasstudiedonthebasisofinformationfromexploratoryboreholes,minesanditsoutcropatthetypelocalityintheLučinaValleyinSilesianOstrava.Locally,theunitattainsathicknessofupto115m(average24.4m).Itspresent-dayareaisapproximately992km2.Theaxisoftheconglomeratefacies(withcharacterofinterbeds)intheunithasaNNE-SSWalignmentandcoincideswiththeaxisofthebasin’smaximumsubsidenceduringthesedimentationofthePorubaMember.Themaximumaggregatethicknessoftheconglomeratefaciesis60m;theirpresent-dayareaofoccurrenceisapproximately480km2.TheCastleConglomerateUnitrepresentsdepositsofalow-sinuosityriversystem.Theupperpartofthemultistoreychannelfillischaracterisedbychannelsfilledwithsandbedformsandoccasionalbars.Palaeocurrentsshowalowspreadofvectors,primarilytotheNNW.Thelowerpartdoesnotcropout;itisknown,therefore,onlyfromboreholes.Thepresenceoftheunit’scoarse-grainedclasticsinsidethebasinfilling,whichisdominatedbysiltstoneandmedium-grainedsandstone,indicatesamajordropinthebaselevel,whichisinterpretedhereasadropinthesealevel.Wecorrelatethiseventwiththemajorglacio-eustaticsealeveldropat323MathatcanbeconnectedwiththeonsetofglaciationintervalC2oftheLatePaleozoicIceAge.Becausetheresolutionofavailablestratigraphicandgeochronologicdataisnotcurrentlysufficient,analternativeexplanationofthetectonicorigincannotberuledoutofthediscussionandmayalsobevalidinregardtotheactiveVariscanforeland.

【 授权许可】

Unknown