Origin of the lithological variation in the sequence of the Sub-Menilite Globigerina Marl at Znamirowice (Eocene-Oligocene transition, Polish Outer Carpathians)
Abstract
Geneza zmienności osadów podmenilitowych margli globigerinowych w Znamirowicach (pogranicze eocenu i oligocenu, Polskie Karpaty Zewnętrzne)
Sediment features, including foraminifera and nannoplankton diversity, δ18O and δ13C signals, total organic carbon content, and type of kerogen show that the combined influence of periodically changing productivity of calcareous material and the intermittent supply of material from land and shelf during one 414 ky eccentricity cycle are the main factors responsible for the pattern of the Sub-Menilite Globigerina Marl sequence at Znamirowice. The vertical fluctuations from calcareous green shale and light-coloured marl to noncalcareous green shale, in the lower part of the sequence, are shown to result primarily from temporary changes in calcareous nannoplankton and planktonic foraminifera productivity. Climate and water circulation changes forced by the 90 ky fluctuation of the Earth’s orbit eccentricity, are presumed to be the chief cause of the productivity variation. Minor fluctuations in carbonate content as well as the distribution of dark-gray to black shale and marl layers are regarded as resulting from changing supply of terrigenous material and mass resedimentation events. Intermittent and regionally changing tectonic activity, together with expansion and lateral shifting of deltaic lobes accompanied by more regular climate changes, are considered as responsible for the supply of terrigenous material.
Sediment features, including foraminifera and nannoplankton diversity, δ18O and δ13C signals, total organic carbon content, and type of kerogen show that the combined influence of periodically changing productivity of calcareous material and the intermittent supply of material from land and shelf during one 414 ky eccentricity cycle are the main factors responsible for the pattern of the Sub-Menilite Globigerina Marl sequence at Znamirowice. The vertical fluctuations from calcareous green shale and light-coloured marl to noncalcareous green shale, in the lower part of the sequence, are shown to result primarily from temporary changes in calcareous nannoplankton and planktonic foraminifera productivity. Climate and water circulation changes forced by the 90 ky fluctuation of the Earth’s orbit eccentricity, are presumed to be the chief cause of the productivity variation. Minor fluctuations in carbonate content as well as the distribution of dark-gray to black shale and marl layers are regarded as resulting from changing supply of terrigenous material and mass resedimentation events. Intermittent and regionally changing tectonic activity, together with expansion and lateral shifting of deltaic lobes accompanied by more regular climate changes, are considered as responsible for the supply of terrigenous material.