© Author(s) 2024. CC Atribution 4.0 License Petrology dataset of Pliocene-Pleistocene sediments in northeastern Slovenia Podatki o petrologiji pliocensko-pleistocenskih sedimentov severovzhodne Slovenije Eva MENCIN GALE1*, Polona KRALJ1, Mirka TRAJANOVA1, Luka GALE1, 2 & Dragomir SKABERNE1 1 Geološki zavod Slovenije, Dimičeva ulica 14, SI–1000 Ljubljana, Slovenija 2 Oddelek za geologijo, Naravoslovnotehniška fakulteta, Aškerčeva 12, 1000 Ljubljana, Slovenija *corresponding author: eva.mencin-gale@geo-zs.si Prejeto / Received 21. 5. 2024; Sprejeto / Accepted 6. 6. 2024; Objavljeno na spletu / Published online 11. 6. 2024 Key words: petrological analysis, clast lithological analysis, provenance of the clasts, Pliocene-Pleistocene sediments Ključne besede: petrografska analiza, litološka analiza klastov, provenienca klastov, pliocensko-pleistocenski sedimenti Abstract This is a dataset of petrological analysis of Pliocene-Pleistocene f luvial sediments from 14 gravely samples from the Slovenj Gradec, Nazarje, Celje and Drava-Ptuj Basin (northeastern Slovenia), collected for clast lithological analysis. The petrological analysis includes description of 155 thin sections of metamorphic, volcanic, volcaniclastic, clastic and carbonate rocks. This dataset provides grounds for determining the provenance of these gravel deposits, revealing possible resedimentation processes, and serves as a tool for drainage network interpretation in the Pliocene-Pleistocene. Izvleček V članku predstavljamo podatke o petrološki analizi rečnih pliocensko-pleistocenskih sedimentov iz 14 prodnatih vzorcev iz slovenjgraškega, nazarskega, celjskega in dravsko-ptujskega bazena (severovzhodna Slovenija), ki so bili vzorčeni za namen litološke analize klastov. Petrološka analiza obsega opise 155 zbruskov metamorfnih, vulkanskih, vulkanoklastičnih, klastičnih in karbonatnih kamnin. Ti podatki predstavljajo temelj za določitev provenience obravnavanih prodnatih sedimentov, razkrivajo morebitno resedimentacijo ter so pomembni za interpretacijo razvoja rečne mreže v pliocenu in pleistocenu. GEOLOGIJA 67/1, 157-160, Ljubljana 2024 https://doi.org/10.5474/geologija.2024.008 Background This dataset was collected to perform clast lith- ological analysis of Pliocene-Pleistocene f luvial sediments in the frame of research published in Mencin Gale (2021). The dataset present in this article contributes to understanding the prove- nance of gravelly sediments deposited in Slovenj Gradec, Nazarje, Celje and Drava-Ptuj Basins us- ing clast lithological analysis. This method pro- vides grounds for determining the source of grav- el. Moreover, it serves as a tool for determination of possible re-sedimentation (e.g. from Miocene conglomerates) and drainage evolution. Clast lithological analysis is traditionally per- formed at the macroscopic level (Bridgland et al., 2012), with efficacy and statistical validity being its primary strengths (Bridgland, 1986; Walden, 2004; Gale and Hoare, 2011). However, it has been discovered that conducting petrographic analysis on thin sections of selected clasts significantly en- hances the quality and spatial resolution of prov- enance analysis (Mencin Gale, 2021; Mencin Gale et al., 2019a, 2019b, 2024). This approach provides more accurate information about the composition and source formations of the studied sediments. Detailed results and interpretations of this methodology were already published in several publications: Mencin Gale (2021), Mencin Gale et al. (2019a, 2019b, 2024). Moreover, the selected sections frow where the samples were taken were in detail discussed in Mencin Gale et al., (2019a, 2019b, 2024). Data Article 158 Eva MENCIN GALE, Polona KRALJ, Mirka TRAJANOVA, Luka GALE & Dragomir SKABERNE Experimental design, materials, and methods a) Gravel sampling We selected 14 sections in Slovenj Gradec, Nazarje, Celje and Drava-Ptuj Basins for sedi- mentological analysis and sampling (Fig. 1). The sections were selected based on length and preser- vation of the clasts (avoiding weathered sections). The sections range from 1 to 14.3 m in length (Table 1). The most suitable outcrops were found on terrace risers or within areas incised by tribu- taries. Samples of gravel were collected from the sections, which were cleaned prior to sampling. Locations of the sections (x, y, z) were acquisited with hand-held GPS device Trimble and further managed in ArcGIS Pro (ESRI). b) Clast lithological analysis (CLA) Clast lithological analysis was adapted from guidelines by Walden (2004), Lindsey et al. (2007), and Gale and Hoare (2011). Sampling for gravel involved bulk sampling of the exposed surface to avoid biasing by selecting only the most obvious clasts. The Velunja section (VE; Velenje Basin) was logged and sampled with an abseiling technique and the rest of the sections were accessible from the ground. Dry-sieving was conducted in the f ield, with only a 1.5–6 cm fraction transported to the laboratory for further analysis. Clasts smaller than 1.5 cm are mostly too weathered to allow for reliable determination of lithology. Larger clasts also allow for better observation of the texture and bulk characteristics of the rock. Each sample comprised 48–346 clasts, with precise counts provided in Table 1. A smaller num- ber of counted clasts is due to the less available material for the analysis (e.g. smaller, conglomer- ated layers). Macroscopic examination and lithol- ogy-based grouping were followed by petrological analysis. In total 2.682 clasts were examined from which 155 were selected for detailed examination in thin sections: 14 clasts from the Slovenj Gra- dec Basin, 63 from the Nazarje Basin, 13 from the Celje Basin, 32 from the Drava-Ptuj Basin, and 33 from the Velenje Basin. Fig. 1. Overview of the studied region. A: Map of Slovenia with marked investigated area. B: Locations of the selected basins and sections comprising the dataset presented in this paper. Basemap: shaded relief of the DEM (digital elevation model, Ministry of Environment & Spatial Planning, 2015). 159Petrology dataset of Pliocene-Pleistocene sediments in northeastern Slovenia c) Microscopy for determination of source stratigraphic unit We used optical polarizing microscope Opton Zeiss for microscopy in transmitted light with lenses with magnifications of 2.5×, 5×, 10×, 20×, 25×, 50×. A digital camera is attached to the mi- croscope for production of microphotographs. Bi- otic components in carbonate and mixed carbon- ate-siliciclastic rocks, grain composition in clastic rocks, and mineral associations and mineral alter- ations in metamorphic, volcanic, and volcaniclas- tic rocks determined from thin sections crucial for the determination of source stratigraphic unit of each rock type. Data description All described and deposited data are analyzed data. They are represented in several figures, ta- bles and shapefile. Fig. 1 shows locality map of the sections. Fig. 2–5 show selected photographs of 35 thin sections in the Slovenj Gradec (5), Nazarje (10), Celje (8) and Drava-Ptuj Basin (12), respectively. Figure 1: Locations of the sections where sam- ples for clast lithological analysis were collected. Figure 2: Microfacies of clasts in the Plio- cene-Pleistocene sediments from the Slovenj Gra- dec Basin in cross-polarized light. Corresponding thin sections descriptions are presented in Table 2. Abbreviations: Qtz – quartz, Mc – microcline, Pl – plagioclase, Ep – epidote, Am – amphibole, Chl – chlorite, Bt – biotite, Ms – muscovite, Grt – garnet Figure 3: Microfacies of clasts in the Plio- cene-Pleistocene sediments from the Nazarje Basin in plain- (A, B, C, D, G, H, I, J, K, L) and cross-polarized light (E, F). Corresponding thin sections descriptions are presented in Table 3. Ab- breviations: H – hyaloclasts, Lmt – laumontite, Chl – chlorite, Sme – smectite, Zeo – zeolite, Pl – plagioclase, PmL – pumice lapilli, VRF – volcanic rock fragment, Fsp – feldspar, Aug – augite, Qtz – quartz, Bt – biotite, Hbl – hornblende, M – glassy groundmass, Px – pyroxene, RF – rock fragment. Figure 4: Microfacies of clasts in the Plio- cene-Pleistocene sediments in the Celje Basin in plain- (B, C, D, E, F, G, I) and cross-polarized light (A, H). Corresponding thin sections descriptions are presented in Table 4. Abbreviations: Qtz – quartz, Ms - muscovite, CG – crystal grains, y-GS – y-shaped glass shards, VRF – volcanic lithic fragment, Fsp – feldspar, M – tuffaceous matrix, Bt – biotite, g – glassy groundmass, RF – rock fragment, Tur – tour- maline, Tur(a) - authigenic tourmaline Figure 5: Microfacies of clasts in the Plio- cene-Pleistocene sediments in the Drava-Ptuj Ba- sin in cross- (A, B, D, G, H, I) and plain-polarized light (C, E, F, J, K, L, M, N, O). Corresponding thin sections descriptions are presented in Table 5. Ab- breviations: Qtz – quartz, Qtz(m) – microcrys- talline quartz, Hbl – hornblende, Ep – epidote, Grt – garnet, Ms – muscovite, Ser – sericite, Chl – chlorite, Chl(a) – altered chloride, Op – opaque mineral, WGS – welded glass shards, Cl – col- lapsed lapilli. Locality map of sections in Shapefile (Shape- f ile 1) contains following attribute: type of shape- file, section (full name), name of the section (ab- breviations), section type, reference, where the results and interpretation are published, author of the mapping and year of mapping. Shapefile con- tains 14 data points. Shapefile 1: Location map of sections Table 1 contain dataset with listed sections in each basin; section names after village name; sec- tions’ lengths in meters; CLA (clast lithological analysis) sample; depth of collected clast lithologi- cal samples; number of counted clasts per sample; number of thin sections per sampling area; coor- dinates of the sections in EPSG Coordinate Refer- ence System Code (code: 3794); cross-reference for petrographical data (Tables 2-5 and publications) and related research article in which results and discussions were presented. Tables 2‒5 contain petrographical dataset of analyzed thin sections from the Slovenj Gradec, Nazarje, Celje and Dra- va-Ptuj Basins, respectively, including lithogroup, lithotype, thin section descriptions and prove- nance attribution. Thin sections are marked with abbreviation of the section and a consecutive num- ber. Lithogroup marks general rock classification. Lithotype represents basic rock determination. Brief petrographic description contains informa- tion about rock structure, texture, mineralogical composition, alteration, weathering, cementation, microfossils, diagenesis and, where applicable, resemblance with a certain thin section. Prove- nance was determined according to petrographic descriptions and compared with published data and maps of the geological units (Mencin Gale et al., 2019a, 2019b, 2024; Mencin Gale, 2021, and references therein). Table 1: Sections dataset Table 2: Petrography Slovenj Gradec Basin Table 3: Petrography Nazarje Basin Table 4: Petrography Celje Basin Table 5: Petrography Drava-Ptuj Basin 160 Eva MENCIN GALE, Polona KRALJ, Mirka TRAJANOVA, Luka GALE & Dragomir SKABERNE Data format Figure 1–5: Raster image (.jpeg format) Shapefile 1: ESRI shapefile, point features (.shp format) Table 1–5: Microsoft Excel file (.xlsx format) Data accessibility The analyzed data and metadata are open ac- cess data and has been deposited in DiRROS re- pository. License: CC-BY 4.0. Data and metadata are accessible using the link: Repository name: DiRROS Direct URL to data: https://dirros.openscience. si/IzpisGradiva.php?id=19042&lang=slv Acknowledgment This work was co-funded by the Slovenian Research and Innovation Agency (ARIS) in the frame of the Young Researchers programme under grant no. 38184, the postdoctoral project under grant no. Z1-50029 (EvoQ the past) and the research programme Regional Geology under grant no. P1-0011 carried out at the Ge- ological Survey of Slovenia. We would like to thank dr. Petra Gostinčar and anonymous reviewer for the com- ments that significantly improved the earlier version of the manuscript. References Bridgland, D.R. 1986: Clast Lithological Analysis. Technical Guide, 3. Quaternary Research As- sociation, Cambridge: 207 p. 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