Cyclicity of the Lower Buntsandstein in the eastern part of the Central European Basin:implications for Early Triassic palaeogeography and for geochronological calibration  

作　　者：Anna Becker 

机构地区：[1]Polish Geological Institute-National Research Institute,4 Rakowiecka str.,00-975 Warsaw,Poland

出　　处：《Journal of Palaeogeography》2024年第2期252-292,共41页古地理学报（英文版）

基　　金：financed from the statutory funds of the Polish Geological Institute-National Research Institute(projects No. 61.2201.0605.00.0 and No.62.9012.2034.00.0)。

摘　　要：Lower Buntsandstein small—scale cycles recognized in the Central European Basin(CEB) are readily used for astrochronological calibration of the Early Triassic time scales,although they are not well studied sedimentologically.Three borehole sections from the eastern part of the CEB,forming a south-north transect perpendicular to the basin axis,were studied in terms to better understand the depositional history of the Lower Buntsandstein developed as the Baltic Formation in the studied Polish part of the basin.Eleven sedimentary facies were recognized,based on lithological and sedimentological investigations of 655.7 m of drill cores from the Otyń IG 1,Gorzów Wielkopolski IG 1 and Kamień Pomorski IG 1 boreholes.The facies can be grouped according to a lithological criterion into facies of predominantly siliciclastic lithology(including 9facies types) and facies of predominantly carbonate lithology(including 2 facies types).Facies analysis allowed to distinguish 8 facies associations of:1) alluvial fan,2) playa,3) sandy-muddy coastal plain,4)embayment and distal delta,5) lagoon,6) sand bars or shoals,7) ooidal shoals or bars,and 8) offshore.Deepening-upward(DC) and shallowing-upward(SC) sedimentary cycles were recognized in parts of the Baltic Formation,with DCs dominating in the southernmost located Otyń IG 1,and SCs dominating in Gorz ow Wielkopolski IG 1,located in the axial part of the basin.Symmetrical cycles are very rare.The statistical significance of the sedimentary cycles is relatively low according to Markov-chain analysis conducted with the phpSedistat software of Stanova et al.(2009).Analysis of small—scale cycles performed on well logs of investigated boreholes and additional boreholes in the vicinity of Otyń IG 1,implementing the earlier study of Becker(2005),showed that the correlation of well-log cycles(GR cycles) and sedimentary cycles is not obvious.GR cycles can be roughly correlated with lithological carbonate—siliciclastic cycles(c-s cycles),reflecting alternations of facies groups o

关 键 词：TRIASSIC Lower Buntsandstein CYCLICITY Central European Basin 

分 类 号：P534.51[天文地球—古生物学与地层学]