Sieniawa Lignite Mine – extraordinary history, geology and mining achievements during the last decade

This time period covers the years 1853–1945. Mining in the Sieniawa area began in 1853, when the Imperial Prussian Mining Office granted a licence for lignite exploitation in the ‘Emiliensglück’ mine. In actual fact, lignite mining did not commence until 1872 (Zdanowicz, 2010). The Sieniawa mine, operating under the name of ‘Vereinigte Emiliensglück’ from 1898 onwards, was initially owned by the von Bockelberg family and later, from 1918 onwards, it belonged to the ‘Anhaltische Kohlenwerke AG’ of Halle in present-day eastern Germany. In those days, mining was conducted underground in saddles I–IV (see Fig. 1C). Prior to 1939, maximum lignite production occasionally reached 0.08 Mt per annum, but, during World War II, the Sieniawa mine was almost completely destroyed (Gontaszewska, 2015; Greinert, 2015).

The Polish history of the Sieniawa mine did not began until 1950, when it was rebuilt after having suffered war damage (Ciuk, 1994; Bik, 2006, 2014). Lignite exploitation commenced in the same year, and has continued uninterrupted to this day. In the years 1950–1997, underground mining was still carried out. Lignite excavation, loading and underground transportation were initially carried out entirely by hand (Greinert, 2015). Later, until 1960, horses were used to pull carts, to be followed by electric locomotives. Lignite from the shaft was transported by cable car to the sorting and loading facility in Sieniawa, where it was finally loaded onto railway wagons and trucks. The cable car was decommissioned in 1986 (Zdanowicz, 2010). Fortunately, some traces of the old mining technology have been preserved to this day (Fig. 2). In the years 1979–1997, simultaneous with underground mining, SLM exploited lignite using the opencast (surface) method, and later become an entirely opencast operation.

Fig. 2.

Preserved traces of old mining technology in the village of Sieniawa. A – Lignite loading/sorting facility and cable car used until 1986 (see https://klimatylagowskie.pl/index.php?pg=start17); B – Same view as in Figure 2A in October 2025; C, D – Renovated cable car and underground train located in front of the SLM management in Sieniawa, September 2015 (photographs 2B–D by authors).

In June 2002, SLM turned private, as a limited liability company, abbreviated SLM Ltd. The opencast exploitation of lignite began on saddle IX – west (no. 15 in Fig. 1B; Zdanowicz, 2010; Galiniak et al., 2011, 2015), followed by saddle VIII – east (no. 17 in Fig. 1B). In these two opencast mines, lignite from the Sieniawa 1 deposit (Kozula, 2002) was exploited. In 2018, lignite mining from the Sieniawa 2 lignite deposit (Gruszecki, 2010) started, i.e. on saddles XI–XIII (nos. 18–20 in Fig. 1B). The production volume and directions of use of the lignite from SLM is discussed below (Subsection 3.4).

Based on the physical and geographical division of Poland outlined by Kondracki (2009), the SLM territory belongs to the Lubusz Lakeland macroregion and the Łagów Lakeland mesoregion. The latter is a strongly glaciotectonically disturbed hilly moraine plateau. Most of the land surface lies above 120 m a.s.l. and the highest hill is known as Bukowiec, which reaches an elevation of 225.4 m a.s.l. Otherwise, relative heights of the terrain range from a few metres to over 100 m (e.g., Studencki, 2000; Winnicki, 2004).

General information. In the study area, the sub-Cenozoic basement is composed primarily of Cretaceous-aged marls and limestones. These rocks are found at average levels of 180–160 m b.s.l., with the possible occurrence of grabens and horsts (Studencki, 2000). Thus, the surroundings of Sieniawa belong to the Szczecin Segment of the Szczecin– Miechów Synclinorium (Żelaźniewicz et al., 2011). In sharp contrast to most Polish lignite deposits, the Sieniawa deposit was completely deformed by the Scandinavian ice sheets during the Pleistocene. Therefore, the lignite beds studied are genetically classified as glaciotectonic types, and fold and thrust/sliced subtypes (Ciuk, 1968; Kasiński & Piwocki, 2002; Widera, 2016).

Comparable to most Polish Lowlands, the Cenozoic depositional history in this area is characterised by relatively marked stratigraphical gaps, i.e. in the Paleocene–Eocene, upper Oligocene and Lower Pliocene–Lower Pleistocene. Hence, the oldest Cenozoic strata are mainly marine glauconitic sands, with terrestrial coaly muds and thin lenses of lignite of early Oligocene age. They form a continuous layer with a thickness of 40–80 m and are, generally, not glaciotectonically deformed (Studencki, 2000; Widera, 2021).

Due to glaciotectonics, and in sharp contrast to the Paleogene, Neogene sediments range in thickness between a few metres and > 300 m (Kozula, 2002; Winnicki, 2004). Their base is dominated by sandy sediments interbedded with gravels, muds and the 3^rd Ścinawa lignite seam. Higher in the succession, the sediment grains become finer and ‘coaly mud’ appears with the 2^nd Lusatian lignite seam (LLS-2; Piwocki & Ziembińska-Tworzydło, 1997; Kasiński et al., 2019; Widera, 2021), this being the subject of exploitation by SLM. The sediments are glaciotectonically arranged in folds and thrusts/nappes, the higher anticlinal parts of which are called saddles (compare Figs. 1 and 3). The depth of these deformations even exceeds 200–250 m (Ciuk, 1968; Winnicki, 2004; Gontaszewska-Piekarz, 2021).

Fig. 3.

Geological cross section A–B through the lignite saddles VIII–XIII (based on Winnicki, 2004; Kot & Widera, 2018; Kasiński et al., 2019). Note the deeply disturbed sediments including lignite seam; for location cross sectional line A–B see Figure 1B.

The Neogene is mainly capped by glaciogenic Quaternary, consisting of tills, gravels, sands and muds (Kozula, 2002; Gruszecki, 2010), all subjected to glaciotectonic deformation; hence their thickness is very diverse and ranges from 0 to ~200 m along the cross sectional line A–B (Fig. 3). For more data on macro- and mesoscale glaciotectonic deformation of both Quaternary and Neogene sediments at SLM outcrops, reference is made to Kot and Widera (2018).

Field research. Description: At the end of 2025, mining activities in SLM were carried out on saddle XIII (see Fig. 1B, 1C). The nearest geological cross section (C–D) is almost parallel to the lignite wall (Fig. 4). Thus, it quite accurately reflects what was seen in the field, i.e., in the opencast mine and its surroundings. It should be noted that SLM only exploits lignite to groundwater level (Fig. 5). Therefore, part of the fold exposed in the field approximately corresponds to what is shown between boreholes 180/74 and 182/74, down to a depth of 120 m a.s.l. (compare Figs. 4 and 5).

Fig. 4.

Geological cross section C–D through the lignite saddles XIII (based on SLM data). For location cross sectional line C–D see Figure 1C and for explanations see Figure 3.

Fig. 5.

Lignite wall and accompanying siliciclastics exposed in October 2025. A – Broad westward view of lignite opencast mine; B – Corresponding line-drawing of what is seen in Figure 5A. Note the complex internal structure of the lignite fold (anticline) and the location of the section examined in detail in Figure 6; for location of lignite wall see Figure 1C and for explanations see Figure 3.

Interpretation: The visible part of the lignite seam represents a standing, and slightly asymmetrical, fold on a macroscale. In contrast, at mesoscale, it is characterised by a very strongly disturbed internal structure, which allows it to be classified as a disharmonic fold (Fig. 5; Davis et al., 2011).

Description: The sedimentary section which was examined in detail is 8 m in length and includes both underlying lignite and overlying lignite deposits, as well as the main lignite seam, i.e. LLS-2. The underburden and overburden consists mainly of coaly mud with an ash yield in the range 64–90 wt%. In contrast, the lignite seam mentioned (with a thickness of 5.6 m) is characterised by ash yield in the range 4–18 wt% and an average of approximately 11.5 wt%. Attention should be paid to the low values of this parameter in samples S18 and S19 (A^d= 4–5 wt%), as well as the significantly higher value in sample S12 (A^d= ~15 wt%) (Fig. 6).

Fig. 6.

Sedimentological log, ash yield, siliciclastic facies and lignite lithotypes with palaeoenvironmental interpretation along the section studied in detail. Note the folded structure of all sediments, as well as the presence of xylites and fusitic fragments within the lignite seam; for location of examined section see Figure 5B; for explanations of facies and lithotype codes see Table 1.

Interpretation: In the samples analysed from LLS-2, there is a clear difference between lignite (samples S8–S40) and non-lignite sediments (samples 1–7 and S41–S43). In the case of this seam, samples S18 and S19 indicate an ombrotrophic mire (A^d<5 wt%), while the remaining ones document a rheotrophic mire (A^d>5 wt%) (e.g., Opluštil et al., 2024). On the other hand, the abrupt increase in ash yield in sample S12, in relation to the surrounding lignite samples, can be interpreted as a result of flooding in the mire area (e.g., Chomiak, 2020).

Description: In the lower part of the lignite seam (LLS-2), two lithotypes were distinguished. The first is a massive and folded detritic lignite (DLm(fo)), while the second is also massive and folded but a xylodetritic lignite (XDLm(fo)). The upper part of LLS-2 includes alternating detritic (black) and weathered detritic (light brown) lignites with an initially horizontal, folded structure (DLh(fo) and WDLh(fo), respectively). It should be emphasised that, in the more weathered layers (but not only those layers), there are lenses, occasionally laminae, and single particles of fusitic lignite, i.e. palaeocharcoal. The accompanying Neogene siliciclastics are mainly horizontally laminated and folded coaly (carbonaceous) muds (MCh(fo)). A thin layer of massive and folded clay (Ym(fo)), was also macroscopically distinguished in the field, reaching a thickness of up to 5 cm (Fig. 6).

Interpretation: Based on the composition of the lignite lithotype, it is possible to determine the initial mire type approximately. Thus, the dominant detritic lignite association (DL) formed in mire sub-environments related to a fen, open water (lake) or a treeless marsh (sea coast), by the following vegetation: aquatic plants, sedges and reeds (Kolcon & Sachsenhofer, 1999; Ticleanu et al., 1999; Widera, 2021; and references therein). According to these researchers, the xylodetritic lignite association (DXL) is attributed to the bush moor. This mire type is also referred to as the Myricaceae–Cyrillaceae swamp (Teichmüller, 1958, 1989). Obviously, the occurrence of the fusitic lignite in SLM is evidence of natural fires (i.e. wildfires) in the mire area and/or within the peat seam (Kwiecińska & Wagner, 1997; Markič & Sachsenhofer, 1997). Less (i.e. massive) or more (i.e. horizontal) stratified lignite structures either formed syn-depositionally or post-depositionally, as a result of hydrological changes in the Neogene mires. In contrast, the folded (and thrust/napped) structure certainly formed post-depositionally, as a result of Pleistocene deforming processes (Ciuk, 1968; Kasiński & Piwocki, 2002; Widera, 2016; Kot & Widera, 2018). The interpreted mineral and organic-mineral sediments from Ym to MCh (compare Table 1 and Fig. 6) were deposited in the lake at deeper (>>2m deep) to shallower zones (>2 m deep), respectively, i.e. outside the reach of reed/sedge-like vegetation (e.g., Kwiecińska & Wagner, 1997; Diessel et al., 2000; Zieliński, 2014; Widera, 2021; and references therein).