Crevasse splays within a lignite seam at the Tomisławice opencast mine near Konin, central Poland: architecture, sedimentology and depositional model
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Date
2020-04
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Instytut Geologii UAM
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Abstract
The present article focuses predominantly on sandy deposits that occur within the Middle Miocene lignite seam at the
Tomisławice opencast mine, owned by the Konin Lignite Mine. As a result of mining activity, these siliciclastics were
available for direct observation in 2015–2016. They are situated between two lignite benches over a distance of ~500
m in the lower part and ~200 m in the higher part of the exploitation levels. The maximum thickness of these sandy
sediments, of a lenticular structure in a S–N cross section, is up to 1.8 m. With the exception of a thin lignite intercalation,
these siliciclastics comprise mainly by fine-grained and well-sorted sands, and only their basal and top layers are
enriched with silt particles and organic matter. Based on a detailed analysis of the sediments studied (i.e., their architecture
and textural-structural features), I present a discussion of their genesis and then propose a model of their formation.
These siliciclastics most likely formed during at least two flood events in the overbank area of a Middle Miocene
meandering or anastomosing river. Following breaching of the natural river levee, the sandy particles (derived mainly
from the main river channel and levees) were deposited on the mire (backswamp) surface in the form of crevasse splays.
After each flooding event, vegetation developed on the top of these siliciclastics; hence, two crevasse-splay bodies (here
referred to as the older and younger) came into existence. As a result, the first Mid-Polish lignite seam at the Tomisławice
opencast mine is currently divided in two by relatively thick siliciclastics, which prevents a significant portion of this
seam from being used for industrial purposes.
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backswamp area, facies analysis, siliciclastic deposition, Neogene
Citation
Geologos 26, 1 (2020): 25–37