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

Abstract

The Kamień Pomorski IG-1 borehole (Pomerania, NW Poland) yields a profile through the Triassic-Jurassic (T-J) transition in continental deposits. An integrated study of the sedimentology, sequence stratigraphy, palynology, biostratigraphy and geochemistry of these deposits has been carried out on the boundary interval, which represents a time of major environmental change. Two lithological units within the transitional section are distinguished: the Lower-Middle Rhaetian Wielichowo Beds of alluvial plain facies, which shows evidence of a semi-arid climate, and the Upper Rhaetian to Lower Hettangian Zagaje Formation, lying above a marked erosional sequence boundary, composed of mudstone-claystone and sandstone deposited in a fluvial-lacustrine environment. Carbon isotope values obtained from palynomaceral separates, and thus reflecting isotopic changes in atmospheric CO 2 , show significant fluctuations through the Rhaetian; the most conspicuous negative δ 13 C org excursion is correlated with the Rhaetian 'initial' excursion and shows two sub-peaks, pointing to short-term carbon-cycle disturbances of lesser magnitude. Above the 'initial' negative excursion, there is a positive excursion followed again by more negative values, representing subordinate fluctuation within a positive excursion and is correlated with the T-J boundary. Seventy-two miospore taxa have been determined from the studied T-J transitional section. Two major palynological assemblages have been distinguished: the lower one, typically Rhaetian, named the Cingulizonates rhaeticus-Limbosporites lundblandii association, which corresponds to the Rhaetipollis-Ricciisporites (= Rhaetipollis-Limbosporites) Zone; and the upper one, typically Hettangian, named the Conbaculatisporites mesozoicus-Dictyophyllidites mortoni-Cerebropollenites thiergartii association (with the age-diagnostic pollen C. thiergartii), which corresponds to the Pinuspollenites-Trachysporites (= Trachysporites-Heliosporites) Zone. The T-J palynofloral turnover occurred in a humid period and is more conspicuous then palynofloral changes observed in Greenland, the Tethyan domain or other parts of NE Europe. The osmium isotope system is studied herein for the first time from T-J continental deposits and shows marked disturbances similar to those measured in marine deposits and attributed to volcanic fallout. Carbon and osmium isotope correlation and coeval increase in polycyclic aromatic hydrocarbon (PAH) content and darkening of miospores confirm that eruptions of the Central Atlantic Magmatic Province (CAMP) contributed to the perturbances in climate and crisis in the terrestrial biosphere. A series of periodical atmospheric loading by CO 2 , CH 4 or alternatively by SO 2 , sulphate aerosols and toxic compounds is inferred to have caused a series of rapid climatic reversals, directly influencing the ecosystem and causing the Triassic floral crisis. A floral turnover period commenced at the 'initial' δ 13 C excursion, with the onset of CAMP volcanism. Obtained values of initial 187 Os...

Climatic disaster at the Triassic-Jurassic boundary - a clay minerals and major elements record from the Polish Basin

“…In Gen er al ized car bon-iso tope curve and palaeoclimatic changes are mod i fied and com piled from Hesselbo et al (2002), Korte et al (2009), Ruhl et al (2009 and Pieñkowski et al (2012). Tri as sic-Ju ras sic bound ary lo ca tion is adapted from Korte et al (2009), andPieñkowski et al (2012), FAD of Psiloceras speleae and Cerebropollenites thiergartii from Hillebrandt et al (2007), and age of "ini tial" neg a tive CIE from White side et al (2010), and Ruhl et al (2010); black strip -the old est CAMP ba salt flow in the Argana Ba sin, Mo rocco (Marzoli et al, 2004;White side et al, 2010), dark grey strip -the old est CAMP ba salt flow in the New ark and Hart ford bas ins, North ern Amer ica (Olsen et al, 2002;White side et al, 2010), light grey strip -the suc ceed ing ba salt flow in the Argana Basin, Mo rocco (Marzoli et al, 2004;White side et al, 2010) Late Rhaetian-Early Hettangian times the dis tance from the near est CAMP vol ca nic erup tions to the Pol ish Ba sin did not exceed 1500 km (Pieñkowski et al, 2014). The Rhaetian was a tectoni cally quiet time, but at the be gin ning of the Hettangian there was a dis tinct fault-re lated tec tonic event (Hakenberg and OEwidrowska, 1997;Poprawa, 1997;Pieñkowski, 2004).…”

“…More over, it was found that at mo spheric CO 2 con cen tra tions had increased ear lier in the Rhaetian (Cleve land et al, 2008;. The ear lier Rhaetian neg a tive car bon iso tope ex cursions clearly pre ceded the Late Rhaetian "ini tial" neg a tive CIE Suan et al, 2011;Lindström et al, 2012;Pieñkowski et al, 2012Pieñkowski et al, , 2014Fig. 1).…”

“…Char ac ter is tic fea tures of this time were profound per tur ba tions in the global biogeochemical cy cle, an increase in at mo spheric CO 2 con tent, global green house warming, and mass ex tinc tion. The Tri as sic-Ju ras sic bound ary (TJB) is char ac ter ized by pro nounced neg a tive ex cur sions in ma rine and ter res trial car bon iso tope re cords (e.g., Pálfy et al, 2001;Hesselbo et al, 2002;Guex et al, 2004;Ward et al, 2004;Galli et al, 2005;Williford et al, 2007;Ruhl et al, 2009;Deenen et al, 2010;White side et al, 2010;Pieñkowski et al, 2012) as well as per tur ba tions to other iso to pic sys tems (Co hen andCoe, 2002, 2007;Kuroda et al, 2010;Callegaro et al, 2012;Pieñkowski et al, 2012) . A ma jor Late Rhaetian "ini tial" neg a tive C iso tope ex cur sion (ini tial CIE) is usu ally sep a rated from a sub se quent long-term Hettangian "main" neg a tive C isotope ex cur sion (main CIE) by a dis tinct pos i tive shift in d 13 C values (Hesselbo et al, 2002(Hesselbo et al, , 2007Schootbrugge et al, 2008;Korte et al, 2009;Pieñkowski et al, 2012;Fig.…”

“…Some au thors, though, have re cently chal lenged the causal link be tween end-Tri as sic meth ane re lease and ter res trial eco sys tem cri sis . In deed, the green house ef fect as a single cause of ter res trial ex tinc tions is chal lenged by many authors, who em pha size en vi ron men tal stress caused by emission of volcanogenic toxic com pounds, soil acid i fi ca tion and suc ces sive rapid cli ma tic re ver sals (Self et al, 2006;Ganino and Arndt, 2009;Schootbrugge et al, 2009;Racki, 2010;Pieñkowski et al, 2012Pieñkowski et al, , 2014Schaller et al, 2012). More over, it was found that at mo spheric CO 2 con cen tra tions had increased ear lier in the Rhaetian (Cleve land et al, 2008;.…”

“…The Sr-iso tope and Os-iso tope re cords in di cate that ero sion and weath er ing of CAMP rocks started in the Hettangian, soon af ter their emplace ment (Co hen andCoe, 2002, 2007). Re cently some authors in di cate two sig nif i cant shifts of the Os-iso tope curve (Kuroda et al, 2010;Pieñkowski et al, 2012) dur ing the Rhaetian that may be at trib uted to a rapid em place ment of the CAMP, fol lowed by a rapid in crease in con ti nen tal weath er ing.…”