ASGP (2024), vol. 94: 1–18

FOUR IN ONE: A NEW CREVASSE-SPLAY COMPLEX IN THE MIDDLE MIOCENE OF CENTRAL POLAND

Marek WIDERA (1*), Mariusz DZIAMARA (2), Jakub KLĘSK (1) & Robert WACHOCKI (2)

1) Institute of Geology, Adam Mickiewicz University, Krygowskiego 12, 61-680 Poznań, Poland; e-mails: widera@amu.edu.pl, jnklesk@gmail.com
2) Konin Lignite Mine, 600-lecia 9, 62-540 Kleczew, Poland; e-mails: dziamara.mariusz@kwbkonin.pl, robert.wachocki@vp.pl
*) Corresponding author

Widera, M., Dziamara, M., Klęsk, J. & Wachocki, R., 2024. Four in one: a new crevasse-splay complex in the middle Miocene of central Poland. Annales Societatis Geologorum Poloniae, 94: 1–18.

Abstract: This article focuses on a newly identified set of crevasse splays in the lignite-bearing Miocene of Poland. The sand bodies studied are situated within the First Mid-Polish Lignite Seam (MPLS-1) in the Tomisławice opencast mine, located near Konin in central Poland. The sand bodies form an alluvial complex of four superposed crevasse splays, separated by lignite layers, 0.1–0.8 m thick. They are considered to be overbank lateral splays, emplaced laterally by a fluvial channel, rather than its terminal splays. Their combined thickness reaches ~5 m, their length is <0.6 km and width <0.4 km, and their total area is ~0.1 km2. Nearly half of the sediments examined are subaerial deposits, while the rest are typical of crevasse-splay microdeltas, accumulated in a floodplain subaqueous environment. The sand bodies with local clay lenses are both underlain and overlain by, as well as interbedded with a range of lignite lithotypes, representing various sub-environments of a mid-Miocene mire (backswamp) realm. The estimated time span for the formation of the entire crevasse-splay complex, recording four short-term floods, is at least 48 kyr. The crevasse-splay complex is one of the best developed in lignite/coal successions worldwide. However, it poses a major technical obstacle to mining activity in the Konin Lignite Mine.

Manuscript received 26 September 2022, accepted 15 November 2023