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标题：Organic-walled dinoflagellate cysts from the Bathonian ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland – a palaeoenvironmental approach
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作者：Przemysław Gedl
期刊名称：Acta geologica Polonica
印刷版ISSN：0001-5709
出版年度：2012
卷号：62
期号：3
页码：439-461
语种：English
出版社：Institute of Geology, University of Warsaw
摘要：A succession of Middle–Upper Bathonian (Subcontractus–Retrocostatum zones) ore-bearing clays exposed at Gnaszyn has been investigated for the presence of dinoflagellate cysts. The assemblages are dominated by Ctenidodinium. However, analysis of diversity shows some subtle differences throughout the succession, possibly related to the palaeoenvironmental conditions in the photic zone. Impoverished assemblages, dominated by Ctenidodinium, occur mainly in monotonous muddy intervals. More diverse assemblages, albeit also dominated by Ctenidodinium, occur in intervals which contain siderite concretion levels. The taxonomic composition of the former assemblage seems to reflect slightly restricted conditions in the photic zone, possibly related to a minor reduction in salinity and/or increase in nutrient availability. More diverse dinoflagellate cyst assemblages reflect periods of less intense terrigenous influx and relatively higher, possibly normal, salinity. These changes were possibly caused by variable intensity of freshwater influx into the basin, controlled by sea-level fluctuations. Sea-level changes may be related to migrations of Tethyan water masses, which were probably partly responsible for the composition of the dinoflagellate cyst assemblages.
关键词：Dinoflagellate cysts;Bathonian;Middle Jurassic;Palaeoenvironment;Orebearing clays;Kraków-Silesia Homocline;Poland