Gravity flow origin of glaciolacustrine sediments in a tectonically active basin (Pleistocen central Poland)

Beata Gruszka, Tomasz Zieliński


Grawitacyjnie redeponowane osady glacilimniczne rowu Kleszczowa (pleistocen centralna Polska)

Pleistocene glaciolacustrine sediments of the Kleszczów Graben near Bełchatów - silts and clays with numerous sand intercalations - record the development and decay a glacial lake in a subsiding basin. The sediments were classified in eight genetic facies. These facies present a wide scope sediments subaqueous redeposition and deposition in the basin - from dense mass flows debris-flow type, through liquefied flows and turbidity currents, to low-energy bottom currents. The facies make the ground for identification of subenvironments and environments in the Pleistocene glacial lake. The individual complexes correspond to various environments within the lake: inclined lake bottom dominated by dense mass flows and fluidal flows, open lake with fine-grained parapelagic deposition, deepened axial part the basin with weak bottom currents, marginal part the lake with distal turbidity currents generated by liver supply. Markov chain statistical analysis was used to determine the succession of sedimentary processes in the different lake environments. Vertical sequences of facies proved that the dense mass flows gradually evolved to more diluted Newtonian flows. The sequences typical turbidites were noted as well as those weak underflows generated by river inflows. The frequency and nature the coarse-grained lake sediments formed by mass flows and turbidity currents testify to tectonically controlled style of sedimentation. Processes of violent redeposition were caused mainly by seismic tremors in the active Kleszczów Graben.

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