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Crevasse splays within a lignite seam at the Tomisławice opencast mine near Konin, central Poland: architecture, sedimentology and depositional model

Authors
  • Chomiak, Lilianna1
  • 1 Adam Mickiewicz University, Poland , (Poland)
Type
Published Article
Journal
Geologos
Publisher
Sciendo
Publication Date
Apr 01, 2020
Volume
26
Issue
1
Pages
25–37
Identifiers
DOI: 10.2478/logos-2020-0002
Source
De Gruyter
Keywords
License
Green

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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