Wartanian glacial sediments: insights into deglaciation of Polish Lowlands and Highlands border for geotourism

The transition zone between the Polish Uplands and the North European Lowland Plain in Central Poland represents the marginal area of the Wartanian stadial of the Odranian glaciation (Turkowska 2006; Wachecka-Kotkowska 2015a, 2015b; Fig. 1). Moraines, kames, and outwash plains in the region offer valuable palaeogeographical insights into the last ice sheet’s transgression and recession dynamics. In the western study area, glacial lobes (Widawka and Rawka, Pilica and Luciąża) intersect, receiving material from NW and NE directions (Turkowska 2006; Wachecka-Kotkowska et al. 2012; Barczuk & Wachecka-Kotkowska 2015; Czubla 2015; Górska-Zabielska & Wachecka-Kotkowska 2015; Król & Wachecka-Kotkowska 2015; Wachecka-Kotkowska 2015a, 2015b). Petrographic analysis of Scandinavian gravels and erratic boulders in glacial and fluvioglacial deposits reflects transgression processes from source areas in Fennoscandia and glacial deposition in the study region. Sedimentological and petrographical studies, with distinct objectives, collectively contribute detailed knowledge of the study area.

Figure 1.

The quantitative petrographic study of gravel fraction, crucial for understanding the dynamics of the percentage of petrographic groups in glacial and glaciofluvial deposits, has been extensively explored (e.g. Górska-Zabielska 2008; Górska-Zabielska et al. 2021). While commonly employed for lithostratigraphic correlation in comparable strata (e.g. Lüttig 1991; Böse & Górska 1995; Woźniak et al. 2009, 2018; Czubla et al. 2019; Górska-Zabielska et al. 2021), petrographic analyses also contribute to regional lithostratigraphic correlation within a chronozone (e.g. Böse & Górska 1995; Zabielski 2006; Kucharska & Pochocka-Szwarc 2012).

Petrographic analysis, coupled with the recognition of Scandinavian indicator erratics, helps identify feeding areas and suggests possible routes during the Wartanian stadial of the Odranian glaciations on the border of the Central Polish Plain and Uplands. These analyses extend lithofacial studies, confirming diversification of lithostratigraphic levels known from the literature (e.g. Kozarski 1995; Czubla 2001; Pettersson 2002; Wysota 2002; Kasprzak 2003; Woźniak et al. 2009, 2018; Wachecka-Kotkowska 2015a, 2015b; Czubla et al. 2019; Górska-Zabielska et al. 2021).

In the study of erratic boulders, their various applications, geological heritage, and contribution to geodiversity are recognised (e.g. Alahuta et al. 2018; Moliner & Mampel 2019; Elmi et al. 2020; Meyer 1981, 2006, 2008; Cai 2021; Górska-Zabielska 2021, 2023). As evidence of geological processes during ground structure formation and glacial transport, erratic boulders archive ongoing geomorphological processes, forming a crucial part of the region’s geoheritage. Many other important benefits/services provided by erratic boulders – educational, ecological, geoconservational, pro-environmental, cultural, aesthetic, signposting, recreational – support the sustainable development of peripheral tourist areas, with geotourism being used as a tool. All these values justify the protection of this unique geological heritage (Motta & Motta 2007).

Considering the societal role of science, we highlight selected erratic rocks with significant geotouristic appeal that are used to target geotourists and nature enthusiasts familiar with geoconservation. Our study delves into the analysis of medium-grained (4–10 mm) gravels and erratic boulders in the five sites, which are located within the geomorphologic border zones of Central Poland, in the SE Łódź region. Various authors (e.g. Wentworth 1922; Schulz 2003; Górska-Zabielska 2010; Vinx 2015; Górska-Zabielska et al. 2020, 2022) suggest that the shortest axis of an erratic boulder should lie between 25 and 50 cm. These deposits, from the Wartanian stadial of the Odranian glaciations (MIS6a – Marine Isotope Stage), are situated along the Central Polish Lowlands and Uplands border, spanning from Radomsko (in the west) to Przedbórz (in the east), including a portion within the interlobal zone (Fig. 1B).

Our study of the geomorphological heritage enhances the dissemination of earth and environmental sciences, improves and stimulates environmental education, and provides geoecosystem services (e.g. Gordon & Barron 2013; Alahuta et al. 2018; Finzi et al. 2021; de Paula Silva et al. 2021; Wolniewicz 2021) for the sustainable economic development of the study area. This, in turn, serves to create a new tourism offer, which is linked to an improvement in the quality of life of local communities (Frey 2021; Drinia et al. 2022).

The present surface of the study region reflects the morphological processes of the last 24 million years. Elevated summits, including Chełmo Hill (323 m a.s.l.) to the south, and Bąkowa Hill (287 m a.s.l.) and Czartoryja (266 m a.s.l.) to the south-east, are intricately connected to the ancient substratum, with visible Paleogene–Neogene erosional history. These structures are situated on the Kodrąb Elevation, enclosing the Łódź Cretaceous Syncline to the south, and lie on the border of the Przedbórz-Małogoszcz Range, Radomsko Hills, and Piotrków Plain.

The current geomorphological landscape results from Odranian glaciation, detailed in studies by Wachecka-Kotkowska (2015a) and Szmidt & Wachecka-Kotkowska (2019). The developmental history unfolded in six stages, encompassing pre-Odranian, Odranian, and Wartanian periods. These stages included the ice sheet’s advance, stagnation, and retreat during the Wartanian stadial. Noteworthy events included the merging of the Widawka Lobe with the Rawka, Pilica, and Luciąża Lobe (Fig. 1A), followed by the ice sheet’s retreat and stagnation. Deglaciation concluded with the retreat of the Pilica and Luciąża eastern lobe, leading to postglacial and post-Wartanian phases. The final stage involved ongoing relief transformation during the Vistulian and Holocene periods.

The diverse lithological and petrographic characteristics of the studied sediments can be attributed to the testing of a multitude of different landforms that occur at the edge of the last ice sheet in the study area (Fig. 1B). Landforms include a terminal moraine hill in Masłowice, an undulating till plateau in Ochotnik, a sedimentary marginal ice-sheet zone in Stobiecko Szlacheckie, a kame hill in Miejskie Pola, and an outwash plain in Rzejowice (Fig. 1B).

The geological and geomorphological diversity categorises the study area as geodiverse (e.g. Gray 2013, 2018, 2019; Kubalíková et al. 2021; de Paula Silva et al. 2021), with significant potential for geotourism development in peripheral or indifferent areas (Smoleński 2012) as a tool for sustainable development (Chrobak et al. 2021; Frey 2021; Drinia et al. 2022). The article aligns with the geoconservation trend in local development strategy by integrating various methods (e.g. Gray 2013, 2018, 2019; Anderson et al. 2015), a crucial factor in preserving geodiversity.

The study focuses on the petrographic composition of Scandinavian glacial and fluvioglacial deposits, particularly medium-sized gravel fractions. These analyses, alongside structural and textural assessments, offer a detailed morphogenesis description of the study area. Tentative assumptions suggest potential differences in petrographic percentages within the marginal forms of the Widawka Lobe and the Rawka, Pilica and Luciąża Lobe (Fig. 1B), based on distinct geomorphological settings. The purpose of these analyses is to confirm or reject this initial hypothesis.

Comparing evidence for the Scandinavian origin of glacial deposits with fluvioglacial deposits from the Wartanian stadial is essential. The authors’ previous research discusses the significance of various lithological deposits for petrographic content (Górska-Zabielska & Wachecka-Kotkowska 2014, 2015).

The vicinity of Przedbórz (SE part of the study area) features numerous outcrops of Cretaceous, Jurassic, and a small Triassic formation (Fig. 1 in Górska-Zabielska et al. 2022). Some morphologically defined outcrops, influenced by lithological formation and structural conditions, contribute to cuesta or resistive relief (see Sala 2011). Petrographic research results are expected to help determine the ice sheet advance direction(s) (Fig. 1B), considering the importance of the bedrock’s configuration.

Petrographic research will also attempt to determine the age of the transgression, the subsequent stages of recession, and the time of development of the individual formations.

In this paper we would like to point out some unique erratic boulders that have the potential to promote geotourism in this peripheral tourist area (Smoleński 2012). By providing expert knowledge on some significant erratic boulders, which are not generally known, we demonstrate the importance of the geoheritage of the study area, and how this can drive the sustainable development of the region (e.g. Frey 2021).

The research was carried out at five study sites (Stobiecko Szlacheckie, Rzejowice, Ochotnik, Masłowice and Miejskie Pola; Fig. 1B), located in exploited gravel pits, sand pits, and old closed outcrops. In the context of the regionalisation of the study area, the locations of the sites and the number and type of samples are presented in Table 1.

A sedimentology analysis, according to Zieliński and Pisarska-Jamroży (2012), was made in the study area. The description of individual actions related to sampling and methods of separation and the petrographic identification of the medium-grain (4–10 mm) fraction has been presented in detail in numerous works (e.g. Górska 2000a, 2000b, 2006; Górska-Zabielska 2007, 2008, 2010; Górska-Zabielska & Zabielski 2010, 2011). The consequent laboratory analyses follow the principles of Cepek (1969), Rutkowski (1995) and Górska (2000a; Table 2.4, p. 31).

In the case of erratic boulders, information was collected in the field on their dimensions, petrographic type, source area, indicative value, and characteristic features. Detailed methodological descriptions are given in other papers (e.g. Lüttig 1991; Meyer & Lüttig 2007; Górska-Zabielska et al. 2020, 2022). The estimated volume and weight (Table 2) were calculated according to the formula proposed by Schulz (1964): 0.523 × length × width × height, assuming 1 m³ = 2.75 t.

Boulders were also examined in the field for the presence of microforms, which are characteristic of the subglacial environment, in which erratics at the base of ice sheets are transported and rubbed against harder material. The rounded edges of a boulder, which indicate transport in high-energy subglacial and inglacial conditions, and surface features typical of the periglacial environment (e.g. aeolian erosion, corrasion, and ridge lines) were documented. Field analysis also included contemporary processes affecting the boulder surface (e.g. exfoliation, corrasion, and colonisation by epilithic flora (e.g. Górska-Zabielska 2020; Górska-Zabielska et al. 2020).

The location of the erratic boulders analysed, as well as their basic characteristics, are given in Table 2. The Scandinavian source areas of the indicator erratics are shown in Figure 3. Photographs were taken by M. Górska-Zabielska in 2021.

The research carried out appears to indicate that in the area of the Przedbórz-Radogoszcz Range, on the border between the Łódź Cretaceous Syncline and the Kodrąb Elevation, marginal forms of the Wartanian ice sheet were formed during mixed deglaciation (Fig. 10). The ice sheet flowed in from the north (Ochotnik site; see Wachecka-Kotkowska 2015b). The dynamics of deglaciation varied and depended on the configuration of the Mesozoic bedrock (Szmidt & Wachecka-Kotkowska 2019). During the transgression, some peaks of the Mesozoic remnant hills above 250 m a.s.l. were nunataks (Wachecka-Kotkowska 2015a; Fig. 10). In the depressions of the Mesozoic subsurface, or between the remnant hills (Miejskie Pola), dead-ice patches were deposited for longer periods, resulting in the formation of kames-like forms. On the other hand, the elevations of the Mesozoic substrate forced the glacier masses to flow uphill, sometimes causing a local standstill of the ice sheet and rapid melting, as in the case of Stobiecko Szlacheckie, which shows a tafloid glacimarginal cone (in the sedimentary margin ice-sheet edge), built of gravelly-sandy sediments (Wachecka-Kotkowska 2015a).

Figure 9.

Figure 10.

The large but varied dynamics of deglaciation is recorded in the structural features of the sediments. Glacimarginal forms are characterised by lithofacies and lithogenetic differentiation. The presence of DSm, Dm diamictons and boulder beds indicates direct contact with the ice sheet during deglaciation. A meltwater diamicton is present in Masłowice, and the basal part of the ice sheet has been documented in Ochotnik. Lithofacies representing St, Sp trough sediments are almost absent at the studied sites, with the exception of sand deposits at Rzejowice. The dominant lithofacies are SGh, Sh, and Sr, indicating glacial sedimentation (Miejskie Pola). The SGh, Sh and Sr lithofacies point to weak flow or its expiration (Miejskie Pola). Most sediments were deposited out of channel and on the floodplain of the terminoglacial cone (Masłowice & Stobiecko Szlacheckie) or in shallow braided troughs on the proximal terminoglacial cone (Ochotnik). The presence of different types of sediment deformation confirms the deglaciation of the ice sheet, which varied in time and space (Wachecka-Kotkowska 2015a).

The studies carried out showed variability in the petrographic composition of medium-grained fluvioglacial and glacial gravels from the area of retreat of the Central Polish glaciations. The main petrographic types are crystalline rocks and limestones of the Lower Palaeozoic. Neither the geomorphological position of the sampled deposits, which is obviously related to the different lithology, nor the location in two different glacial lobes influenced the percentage content of petrographic type in the analysed gravels. The main factor that differentiates the petrographic composition of the sediments must be associated with separate advances of the ice sheet. Therefore, the thesis about the influence of weathering on the petrographic composition, which is often mentioned in the literature (e.g. Lisicki 1998, 2000, 2003; Czubla 2001; Woźniak 2004), must be rejected in the case of the analysed material. No such regularity was observed.

Due to the small number of petrographic samples (4–10 mm) analysed in this study, it is not possible to determine the direction in which the ice sheet moved. However, our previous studies (Górska-Zabielska & Wachecka-Kotkowska 2014, 2015) in medium and coarse gravel fractions confirmed the initial hypothesis that this is the zone where two ice-sheet lobes came into contact – namely Widawka Lobe and Rawka, Pilica and Luciąża Lobe. Thanks to the results of complex petrographic analysis, it is possible to determine the directions of advance of the ice masses from NE, NNW (the Widawka Lobe) and NE, NEE (the Rawka, Pilica and Luciąża Lobe).

Evidence of periglacial and contemporary morphogenetic processes is visible on the surface of some of the erratics. All these elements constitute the scientific values of erratic boulders; therefore, they should be considered as geosites (Reynard 2004; Migoń 2012).

Erratic boulders have cultural value; boulders 3, 5 and 7 have their own names, and boulders 3 and 8 have additional legends. Due to their size, the erratic boulders have an aesthetic value. With the exception of boulder 9, all are protected as monuments of inanimate nature. Only one boulder (no. 3) is registered as a geosite in the Central Register of Polish Geosites (https://cbdgportal.pgi.gov.pl/geostanowiska/).

The erratic boulders described above already provide geoecosystem services such as: cognitive, educational, pro-environmental, cultural, conservational, recreational, signposting, and aesthetic (see Finzi et al. 2021; da Silva et al. 2022; Lima & Pereira 2023). There seem to be no contraindications to continuing to perform these functions in the future. Above all, these important geosites should be protected – their in situ conservation is an important task, as it provides present and future generations of researchers with the opportunity to understand the Earth’s history, past environmental changes, and geological phenomena (e.g. Urban et al. 2022; Rodrigues et al. 2023).

Erratic boulders (even monuments of abiotic nature) are being lost for different reasons from the environment due to a lack of knowledge in the community (e.g. Piotrowski 2008; Chrząszczewski 2009). Therefore, there is a need for continuous education to raise the awareness of the local population who have inherited the geological assets of the region (e.g. Urban et al. 2022; Rodrigues et al. 2023). The importance of geoeducation in the promotion of the local geological heritage is highlighted in a recent article published by Górska-Zabielska (2023). Landscapes deprived of erratic rocks lose their geodiversity.

Our ability to apply this knowledge of erratic rocks in the environment is important for the sustainable development of the region. Erratic boulders and, more generally, rock specimens that are typical of the immediate environment have considerable potential for the development of local geotourism. In the literature, there are numerous examples of the use of such objects in educational, sightseeing, and nature tourism (e.g. Górska-Zabielska & Dobracki 2015; Moliner & Mampel 2019; Elmi et al. 2020; Cai 2021; Górska-Zabielska 2021). Erratic boulders may also be used in geowatching (Garofano 2015). Knowledge transfer raises the awareness of the recipients (e.g. tourists, visitors, holidaymakers, Green Schools), so that familiar erratics speak to recipients who are already able to appreciate the geological heritage of their own country. As communication is a tool for protection (Garofano 2015; Urban et al. 2022; Rodrigues et al. 2023), it is only a small step to care for the protection of an erratic – a witness of the glacial age.

In this way, boulders can be a driving force for the sustainable development of local communities. They bring economic benefits to all those involved in the exhibition and geo-interpretation of erratic rocks, including the initiators of the idea, landscape architects, transport and crane operators, designers and producers of information boards and labels, as well as geo-interpreters, maintenance service workers, who take care of the objects’ protection (volunteer eco-patrol, cleaning the surface of the rock from graffiti and lichen), and ensure the safety of geotourists. It should not be forgotten that an effective geo-interpreter and/or a clear set of information panels are needed to share the knowledge.

Key findings are detailed in this chapter. The focus is on the diversity of glacial sediments in different geomorphological settings and their geoecosystem services. Special attention is paid to geotourism. This is a successful driver for sustainable development in a peripheral region.