Sedimentological, palynological and geochemical studies of the terrestrial Triassic–Jurassic boundary in northwestern Poland

摘要: The Kamien Pomorski IG-1 borehole (Pomerania, NW Poland) yields a profile through the Triassic–Jurassic (T–J) transition in continental deposits. An integrated study of sedimentology, sequence stratigraphy, palynology, biostratigraphy and geochemistry these deposits has been carried out on boundary interval, which represents time major environmental change. Two lithological units within transitional section are distinguished: Lower–Middle Rhaetian Wielichowo Beds alluvial plain facies, shows evidence semi-arid climate, Upper to Lower Hettangian Zagaje Formation, lying above marked erosional boundary, composed mudstone-claystone sandstone deposited fluvial-lacustrine environment. Carbon isotope values obtained from palynomaceral separates, thus reflecting isotopic changes atmospheric CO 2 , show significant fluctuations Rhaetian; most conspicuous negative δ 13 C org excursion is correlated with ‘initial’ two sub-peaks, pointing short-term carbon-cycle disturbances lesser magnitude. Above excursion, there positive followed again by more values, representing subordinate fluctuation T–J boundary. Seventy-two miospore taxa have determined studied section. palynological assemblages lower one, typically Rhaetian, named Cingulizonates rhaeticus – Limbosporites lundblandii association, corresponds Rhaetipollis Ricciisporites (= ) Zone; upper Hettangian, Conbaculatisporites mesozoicus– Dictyophyllidites mortoni Cerebropollenites thiergartii association (with age-diagnostic pollen . ), Pinuspollenites–Trachysporites ( = Trachysporites–Heliosporites Zone. palynofloral turnover occurred humid period then observed Greenland, Tethyan domain or other parts NE Europe. osmium system herein for first similar those measured marine attributed volcanic fallout. correlation coeval increase polycyclic aromatic hydrocarbon (PAH) content darkening miospores confirm that eruptions Central Atlantic Magmatic Province (CAMP) contributed perturbances climate crisis terrestrial biosphere. A series periodical loading CH 4 alternatively SO sulphate aerosols toxic compounds inferred caused rapid climatic reversals, directly influencing ecosystem causing Triassic floral crisis. commenced at onset CAMP volcanism. Obtained initial 187 Os/ 186 Os between 2.905 4.873 very low iridium (about 5 ppt) lend no support role an extraterrestrial impact event. position carbon about 12 m below boundaries (emergence surfaces) excursions allow reliable profiles, including St Audrie9s Bay (UK), Csovar (Hungary) GSSP Kuhjoch (Austria).