Paleoenvironments during the Rhaetian transgression and the colonization history of marine biota in the Fatric Unit (Western Carpathians)

Abstract

Abstract:Terminal Triassic environmental changes are characterized by an integrated study of lithology, litho-and cyclostratigraphy, paleontology, mineralogy, geochemistry and rock magnetism in the Tatra Mts. The Carpathian Keuper sequence was deposited in an arid environment with only seasonal rivers, temporal lakes and swamps with scarce vegetation. Combination of a wide range of 18 O values (-0.7 to + 2.7) with negative 13 C values documents dolomite precipitation either from brackish or hypersaline lake water, or its derivation from pore water comparably to the Recent Coorong B-dolostone. Negative 13 C values indicate microbial C productivity. Rhaetian transgressive deposits with restricted Rhaetavicula fauna accumulated in nearshore swamps and lagoons. Associations of foraminifers, bivalves and sharks in the Zliechov Basin were controlled by physical factors. Bivalve mollusc biostromes were repetitively destroyed by storms, and temporary firm bottoms were colonized by oysters and burrowers. Subsequent black shale deposition recorded input of eolian dust. Bottom colonization by pachyodont bivalves, brachiopod and corals started much later, during highstand conditions. Facies evolution also revealed by geochemical data, C and O isotope curves reflect eustatic and climatic changes and help reconstruct the evolution of Rhaetian marine carbonate ramp. The Fatra Formation consists of 100 kyr eccentricity and 40 kyr obliquity cycles; much finer rhythmicity may record monsoonlike climatic fluctuations. Fluvial and eolian events were indicated by analysis of grain size and content of clastic quartz, concentrations of foraminiferal (Agathammina) tests in thin laminae indicates marine ingression events. Magnetic susceptibility (MS) variations reflect the distribution of authigenic and detrital constituents in the sequence. Increasing trend of MS correlates with the regressive Carpathian Keuper sequence and culminates within the bottom part of the Fatra Formation. Decreasing trend of MS is observed upwards the transgressive deposits of the Fatra Formation.

Latest Triassic climate humidification and kaolinite formation (Western Carpathians, Tatric Unit of the Tatra Mts)

“…Cal car e ous sand stones are depleted in REE but de tailed N-PAAS pat terns (Fig. 15A, C) did not re cover the REE trend typ i cal of ma rine car bon ate where MREE ac cu mu late (in phos phates) or are en riched by diagenesis (Shields and Webb, 2004;Haley et al, 2004;Ounis et al, 2008;Michalík et al, 2013). The REE-pat tern of beds 37 to 44 can be re garded as a sign of re cy cled sil i cates only (Fig.…”

“…The d 13 C org val ues of beds 46-55 are more neg a tive (-27 to -28‰; Fig. 11), be ing com pa ra ble e.g., with val ues of or ganic mat ter ana lysed from shal low-ma rine car bon ate and sil i cate rocks across the Tri as sic-Ju ras sic bound ary se quence doc umented in the Zliechov Ba sin of the Fatric Unit (Michalík et al, 2011(Michalík et al, , 2013 and else where (Pálfy et al, 2001;Hesselbo et al, 2002;Kuerschner et al, 2007). How ever, any spec u la tion on the sig nif i cance of the rel a tive shift of d 13 C org is lim ited by our abil ity to prove the strati graphic con ti nu ity of the Tomanová Fm.…”

“…Szulc (in Feist-Burkhard et al, 2008) pro posed a mid-Rhaetian trans gres sion in the German Ba sin. The lithostratigraphy of top Tri as sic se quence of Alpine-Carpathian shelf does not sup port this age de ter mi na tion due to the lack (or rar ity) of in dex fos sils: the ma rine Koessen Forma tion over lies the Plattenkalk in the Al pine Bajuvaric Zone, the Fatra For ma tion fol lows the Carpathian Keuper in the Fatric Zone (Michalík et al, 2013). The Hybe and Norovica for ma tions oc cur on top of the Dachstein Lime stone in the Hronic Zone of the Western Carpathians.…”

“…Carpathian Keuper strata were de pos ited in a dry and hot cli mate on an emer gent Mid dle Tri as sic car bon ate ramp (Al-Juboury and Ïuroviè, 1992;Jaglarz and Szulc, 2003;Jaglarz, 2010). A var ie gated claystone suc ces sion of Carpathian Keuper is de vel oped in two fa cies: a more prox i mal red-bed fa cies con tains siliciclastic in ter ca la tions, while a more dis tal vi o let suc ces sion is in ter ca lated by dolostone lay ers in dicat ing short-lived ma rine in gres sions (Michalík, 1994;Rychliñski, 2008;Michalík et al, 2013). The Keuper strata are mostly de void of in dex fos sils and so their age de ter mi na tion is dif fi cult.…”

Application of magnetic susceptibility as a paleoclimatic proxy on Paleozoic sedimentary rocks and characterization of the magnetic signal – IGCP-580 projects and events

“…The magnetic susceptibility evolution of different marine sediment sections was compared with the sedimentological evolution and it was showed in different cases that MS is strongly influenced by sea level variations and that it can be used for correlations between different sections, mostly in the same basin (Babek et al, 2013;Bertola et al, 2013;Da Silva et al, 2013;Grabowski et al, 2013;Michalik et al, 2013;Pas et al, 2013). A close link between MS and Al, Zr, Ti and other lithogenic elements was also observed on different sedimentary successions, implying that MS can be interpreted as a proxy for detrital inputs (Da Silva et al, 2013;Grabowski et al, 2013;Pas et al, 2013).…”