Sequence stratigraphy, palynology and biostratigraphy across the Ordovician-Silurian boundary in the Röstånga-1 core, southern Sweden

摘要: A multiproxy study on sedimentary rocks spanning the Ordovician-Silurian boundary has been performed material from Rostanga-1 core, with aims to improve biostratigraphical and sedimentological framework interpret depositional environment during this interval in Earth’s history. The succession core is developed Scanian Lithofacies Belt considered an excellent upper Middle Ordovician-Lower Silurian reference section for southernmost Sweden. studied includes Sularp Shale, Skagen Limestone (early middle Katian), Mossen-Fjacka formations, Lindegard Mudstone Kallholn Formation. results study, which sedimentological, palynological stratigraphical investigations, add knowledge climatic changes across boundary. During time covered drill intense Ordovician volcanism was climaxed by a short-lived glacial pulse turn led eustatic regression. evidenced several K-bentonite beds core. This event left its signature as development of sequence solution structures at top Limestone. regressive phase rapidly succeeded return deeper-water conditions evident within succession, implying that rate glacio-eustatic regression greater than subsidence Scania. deglaciation phase, anoxic black shale coincides flooding surface base Fjacka Shale. possibly signifies high palaeo-productivity preservation. Following marks sea-level highstand stable environment. Based results, subdivided into three informal local palynozones. Palynozone I late Katian (pre-Hirnantian Ashgill) age characterized occurrence following acritach taxa: Baltisphaeridium, Buedingiisphaeridium balticum Orthosphaeridium inflatum. cryptospores palynozone provides oldest evidence early land plants Baltica. Through part palynozone, diagnostic Early-Middle reworked acritarchs such Striatotheca, Coryphidium Acanthodiacrodium spp. indicates detrital Avalonian input front Caledonian Deformation foreland-type sedimentation. II ranges Hirnantian-latest Hirnantian long-ranging tolerant acritarch taxa Veryhachium Micrhystridium major micro-phytoplankton turnover recognized appearance affinity, including Ammonidium spp., Diexallophasis denticulate first Baltic record Tylotopalla caelamenicutis. cryptospore assemblage, through II, comprises have reported coeval assemblages globally, indicating homogeneous plant assemblages. palynofacies reveal relatively abundance diversity scolecodonts coupled decrease relative chitinozoans reflecting regional similarity previous results. III latest Hirnantian-early Llandovery (Rhuddanian) graptolites sphaeromorph acritarchs. Formation, comprising rests maximum sea level rise related deglaciation, marking new show lowest abundance, corresponding general feature start Silurian, might be “crisis”. are brownish black, Thermal Alteration Index (TAI) 4 post-mature regard oil generation. There many controls burial magmatic heating had effect thermal maturity organic matter basin.