Origin of the Sub-Menilite Globigerina Marl (Eocene-Oligocene transition) in the Polish Outer Carpathians

Stanisław Leszczyński


Geneza utworów sekwencji podmenilitowych margli globigerinowych (przełomu eocenu i oligocenu) Karpat Polskich

Sediment features, including foraminifera and nannoplankton content. δ18O, δ13C and δ34S signals, TOC and kerogen type, together with sequence patterns, were analysed to interpret the origin of the Sub-Menilite globigerina marl sequence (SMGMS) in the Polish Carpathians. Hemipelagites and fine-grained turbidites are shown to represent the dominant deposits of the SMGMS. The entire unit is interpreted to have originated primarily from increased calcareous nannoplankton and foraminifera production and consequently lowered calcite compensation depth (CCD) due to climate evolution within one long eccentrcity cycle (414 ky). Climatic changes forced by the obliquity (41 ky) and the short eccentricity cycles (ca. 100 ky) are suggested to be of the primary responsibility for the distinctive vertical fluctuation of the CaCO3 content in the fine-grained deposits of the SMGMS. Lateral changes in the fluctuation patterns are interpreted as due to the highly contrasted morphology of the seafloor relative to the CCD. This factor, together with the regionally varying supply of terrigenous material, were responsible for the lateral sequence changes. The clastic supply was controlled by the orbitally forced climate changes and varied tectonic activity in the area. The SMGMS was not formed in areas typified by high terrigenous input.

Enhanced resedimentalion of organic and siliciclastic material and oceanographic changes that lowered carbonate production, were the main factors responsible for the retreat of the SMGM facies and the onset of the Menilite beds.

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