LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST POZNO PLEISTOCENSKI JEZERSKI SEDIMENTI IN NJIHOV A POVEZAV A Z RDEČIMI TLEMI NA SEVEROVZHODNEM ROBU DINARSKEGA KRASA Nadja ZUPAN HAJNA 1 *, Bojan OTONIČAR 1 , Petr PRUNER 1, 2 , Metka CULIBERG 3 , Jaroslav HLAV ÁČ 2, 5 , Oleg MANDIĆ 4 , Roman SKÁLA 2 & Pavel BOSÁK 1, 2 Abstract UDC 551.435.8:551.435.25(497.434)"628.62" Nadja Zupan Hajna, Bojan Otoničar, Petr Pruner, Metka Cu- liberg, Jaroslav Hlaváč, Oleg Mandić, Roman Skála & Pavel Bosák: Late Pleistocene lacustrine sediments and their rela- tion to red soils in the Northeastern margin of the Dinaric Karst A large karst doline at section Hrastje – Lešnica in the Dolenjs- ka region (SE Slovenia) was uncovered during the construction of Slovene highway No. A2. Its fill consists of brownish-yellow clay to silt with plant remains and ferrugineous coatings after root casts and gastropods (paleosol horizon) in the bottom, and overlying thick lacustrine laminated grey clayey sediments which were partly rubified. Brownish-yellow clay to silt con- tains quartz, chlorite, muscovite and feldspars transported as external clastic material from evolved karst and non-carbonate landscapes from surroundings into the site. The material is well weathered only in the area of the paleosol horizon. The strongly impoverished malacocoenosis indicates any Quater- nary warm phase characterized by light semi-open forest with patches of open ground habitats. Only the last paleomagnet- ic sample in the bottom of sediment sequence shows reverse polarity of magnetic field and represents the geomagnetic ex- cursion, i.e., the Blake excursion at ca 120–112 ka (MIS 5e), rather than Brunhes/Matuyama boundary at 0.78 Ma (MIS 19). Thick lacustrine laminated grey clayey sediments above Izvleček UDK 551.435.8:551.435.25(497.434)"628.62" Nadja Zupan Hajna, Bojan Otoničar, Petr Pruner, Metka Cu- liberg, Jaroslav Hlaváč, Oleg Mandić, Roman Skála & Pavel Bosák: Pozno pleistocenski jezerski sedimenti in njihova po- vezava z rdečimi tlemi na severovzhodnem robu Dinarskega krasa Na Dolenjskem krasu je bila med graditvijo trase A2 slovenskega avtocestnega križa na odseku Hrastje–Lešnica razgaljena večja vrtača. V spodnjem delu je bila povsem zapolnjena z rjavkasto- rumenim sedimentom glinene do meljaste frakcije, v zgornjem delu pa z debelim zaporedjem laminiranega sivega glinenega sedimenta, ki je bil ponekod rahlo rubificiran. Rjavkasto rumeni glineni do meljasti sediment na dnu vrtače, v katerem so posa- mezni rastlinski ostanki, s koreninami povezane ferigene skorje in gastropodi (paleotalni horizont), vsebuje kremen, klorit, mus- kovit in plagioklaze. Ti so bili preneseni v vrtačo kot klastični material z bližnjih območij razvijajočega se kraškega in nekar- bonatnega (fluvialnega) površja. Dobro preperel material je le v območju paleotalnega horizonta. Močno osiromašena malako- cenoza nakazuje eno od toplih faz kvartarja, ko so prevladovali svetli gozdovi z redkimi drevesi in jasami odprtih talnih habita- tov. Samo zadnji od paleomagnetnih vzorcev na dnu raziskanega sedimentnega zaporedja kaže reverzno polarnost magnetnega polja. Menimo, da ta reverzna polarnost kaže na t. i. Blakeovo geomagnetno ekskurzijo pred cca 120.000 in 112.000 leti (MIS 1 ZRC SAZU Karst Research Institute, Titov trg 2, 6230 Postojna, Slovenia; zupan@zrc-sazu.si; e-mail: otonicar@zrc-sazu.si 2 Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, 165 00 Praha 6, Czech Republic; e-mail: pruner@gli.cas; skala@gli.cas.cz; bosak@gli.cas.cz 3 ZRC SAZU Jovan Hadži Institute of Biology, Zagorica 20, 1292 Ig, Slovenia 4 Geological-Paleontological Department, Natural History Museum Vienna, Burgring 7, A-1010 Vienna, Austria; e-mail: oleg.mandic@NHM-WIEN.AC.AT 5 Department of Zoology, Museum of Natural History, National Museum, Václavské náměstí 68, 115 79 Praha 1, Czech Republic; e-mail: jaroslav.hlavac@nm.cz * Corresponding author: e-mail: zupan@zrc-sazu.si Received/Prejeto: 07.11.2018 DOI: https://doi.org/10.3986/ac.v48i2.7080 COBISS: 1.01 ACTA CARSOLOGICA 48/2, 153-171, POSTOJNA 2019 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK INTRODUCTION Thick red soils of the Dolenjska region (SE Slovenia; Fig. 1) are predominantly determined as relict soils (Grčman et al. 2015). Their origin and relationship to underlying carbonates and existing karst relief has been, and still is, the subject of discussion. Different opinions were related to the nature of parent material and origin of the red soils (terra rossa; Gregorič 1969; Gams & Vrišer 1998; Rejšek et al. 2012). Terra rossa-type red soils are composed of reddish clayey to silty material covering karst landscapes in hot/warm climates such as those in the Mediterranean part of Dinaric Karst. Terra rossa may have formed exclusively from the insoluble residue of carbonates in some isolated karst, but more often it comprises a variety of parent materials, especially aeolian siliciclastic and/or volcanic dust, vol- canic and/or clastic sedimentary rocks (e.g., Andrusov et al. 1958; Durn 2003). Most authors believe that terra rossa represents polygenetic relict soil formed during the Tertiary and/or warm and humid periods of Quaternary (see Fedoroff & Courty 2014). The low karst of Dolenjska (sensu Gams 1974 or Kranjc 1990; Fig. 1) is covered by Plio-Quaternary de- posits with variable lithologies (Grimšičar 1954; Buser 1974; Gams 1974; Pleničar et al. 1977; Habič 1992; Zupan Hajna 1992; Markič 2009). Thick layers of red deposits prevail (Gregorič 1969; Gams & Vrišer 1998). Although “reddish-brown soils” form a distinctive feature of the Dinaric karst landscapes, no integrated study has been performed in the Dolenjska region; their source has been still unknown as well. Based on few analyses, Gregorič (1969) and Rejšek et al. (2012) interpreted them as in situ or partly re-deposited weathering products cover- ing carbonate rocks. In addition, also relatively homog- enous yellowish sands laterally and vertically alternate with clayey material or fill irregularities of karst surface (mainly subcutaneous shafts and karren; e.g., Habič 1992; Zupan Hajna 1992; Knez & Slabe 2006) in the same re- gions (see Otoničar et al. 2006). Grey montmorillonitic (“bentonite”) clays are locally reported on karst relief and were interpreted as weathered residues of volcanoclas- 5e) in ne meje Brunhes/Matuyama pred 780.000 leti (MIS 19). Tudi v debelem zaporedju sivih laminiranih glinastih jezerskih sedimentov prevladujejo med minerali kremen, muskovit, klorit in glinenci. Glede na ohranjenost glinenih mineralov, muskovita in klorita sklepamo, da so ti sedimenti skoraj neprepereli; rahlo so rubificirani le na površju, v osrednjem delu profila in na stiku z zakraselo podlago vrtače. Mineraloška sestava sivih sedimen- tov je drugačna kot v spodaj ležečem talnem horizontu, kjer je manj kremena in klorita, razlikuje pa se tudi od nekarbonatnega preperinskega ostanka apnenčaste prikamnine. Kot tak torej siv sediment ni izvorni material na sosednjih območjih pogoste terre rosse (poligenetska rdeča tla, razvita v pleoklimatskih razmerah, podobnih današnjemu mediteranskemu podnebju). Laminirani sedimenti so se odložili v razmeroma hladnem obdobju. Do- kaj siromašen palinospekter lahko kaže po eni strani, da so bila pelodna zrna odstranjena iz depocentra s tekočo vodo, po drugi pa na visoko hitrost sedimentacije. V prid temu procesu pritrju- jejo tudi premalo centrirane paleosekularne variacije. Rastlinske združbe nakazujejo, da je bila bližnja okolica v glavnem porasla z obrežnimi gozdovi zmernega podnebnega pasu, kjer so se v humidnih obdobjih poplavljenih ravnic občasno pojavljala tudi mokrišča in manjše ojezeritve. Regionalne korelacije, ki temeljijo predvsem na veliki količini pelodov bukve (Fagus) kažejo, da so se sivi glinasti sedimenti odlagali v toplejšem obdobju na začetku zadnjega poledenitvenega cikla (Würm) med t. i. MIS 5c pred okoli 105.000 do 95.000 leti. Vsi paleomagnetni vzorci tega dela sedimentnega profila kažejo normalno magnetizacijo in zane- marljivo rotacijo 1,8° ± 4,7° v smeri urinega kazalca. Ključne besede: kraški sedimenti, mineralogija, polži, pal- inologija, paleomagnetizem, paleookolje, Dolenjska, Slovenija. are also dominated by quartz, muscovite, chlorite and feldspar. That overlying sediment was almost unweathered (content of feldspars, muscovite and chlorite); it was only slightly rubified on its surface, in middle part of the section and at the contact with the underlying karstified limestone slope of the depres- sion. The grey sediment has a different mineralogical compo- sition than underlying soils (e.g., lack of quartz, chlorite) and non-carbonate residue of the host limestone. Therefore, the grey sediments could not serve as a parent (source) material for terra rossa formation in the broader area (i.e., polygenetic red soils developed in paleoclimate related to current Mediter- ranean climatic conditions). Laminated grey sediment was de- posited in a rather cold climate. Relatively poor palynospectra may indicate transport of pollen grains out of the depocentre with flowing water and/or the rapid deposition. The latter is supported by insufficiently centered paleosecular variations. Plant assemblages indicate that the dominant cover of the sur- rounding landscape was temperate climatic zone riparian forest with some quite humid environment as wetlands and ponds on periodically flooded plain. The regional correlation, based es- pecially on an abundance of Fagus, indicates the deposition at the beginning of the last glacial cycle (Würmian) in its warmer substage – MIS 5c (ca 105–95 ka). All paleomagnetic samples from this part of the sediment section show normal magnetiza- tion and negligible clockwise rotation of 1.8° ± 4.7°. Key words: karst sediments, mineralogy, gastropods, palynol- ogy, paleomagnetism, paleoenvironment, Dolenjska region, Slovenia. ACTA CARSOLOGICA 48/2 – 2019 154 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST tic material (Grimšičar 1954; Pleničar et al. 1977). They had been excavated for the ceramic industry some 3 km from our studied site north of Novo mesto (Pleničar et al. 1977). Chert pebbles derived from different Mesozoic carbonate host rocks are relatively common in such clays or loams in places (Buser 1974; Pleničar et al., 1977; Zu- pan Hajna 1992; Otoničar et al. 2013). Grimšičar (1954) noted that bentonitic clays should be older than Pliocene fluvial sands of the Krško Basin. Mineralogical analyses of various quartz-contain- ing sediments from the cover of the Dolenjska karst indi- cate that at least two types of quartz occur in sediments: (i) weathered residue of dissolution of chert-containing carbonate rocks, and (ii) allogenic quartz sand weath- ered to a different degree (Zupan Hajna 1992). All of the above-mentioned sediments may represent potential source of red soils in the Dolenjska region. The construction of highway A2 Karavanke – Obrežje (Austria – Croatia) north of Novo mesto at sec- tion Hrastje – Lešnica (45°51´11.07˝N; 15°08´36.21˝E; Fig. 1) uncovered laminated sediments filling a large karst depression (a doline). The central part of the doline was filled with grey to locally greenish-grey laminated and thinly-bedded clayey deposits (Fig. 2). They clearly contrasted to thick reddish-brown homogenous soils that cover karstified Mesozoic carbonates in the nearby vicinity and in the wider region. Nevertheless, the grey sediments reveal a gradual lateral transition through brownish-grey and mottled horizon to reddish-brown clayey deposit at the contact with red soils and the weath- ered limestone slope of the depression (Fig. 2). Our working hypothesis was based on the assump- tion that the grey non-weathered laminated sediments might represent the source material for thick red soil – Fig. 1: Location of the studied karst sediments at Hrastje (red dot) in the Dolenjska region, which represents the NE part of Dinaric karst. Source of DEM data: Geodetski oddelek ARSO. Fig. 2: Construction of the highway north of Novo mesto has exposed laminated grey sediments, which were surrounded by red soils devel- oped on subcutaneous karst relief. ACTA CARSOLOGICA 48/2 – 2019 155 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK Fig. 3: Geological map of the studied area (upper; after Otoničar et al. 2006) and digital relief model of location area (lower; on both studied sequence Hrastje is marked by red dot. Source: Geology – OGK 1:100000 Novo mesto, Geološki Zavod Slovenije (Pleničar et al 1977); DEM data – Lidar data, Geodetski oddelek ARSO. Legend: 1 – Massive coarse-crystalline dolomite and limestone; Lower part of Upper Triassic; 2 – Thick bedded Main Dolomite; Upper Triassic; 3 – Micritic and oolitic limestone and bituminous dolomite; Lower Jurassic; 4 – Reef limestone with corals and stromatoporids; Lower part of Upper Jurassic; 5 – Oolitic and micritic limestone; upper part of Upper Jurassic; 6 – Red clayey limestone to marlstone; Upper Cretaceous; 7 – Alternation of marlstone, claystone and sandstone –flyschoid clastics; Upper Cretaceous; 8 – Brown clay, terra rossa and loam; Pliocene and Quaternary; 9 – Fluvial sediments (gravel, sand, silt and clay); Quaternary; 10 – Fault; 11 – Highway profile No. (HP). ACTA CARSOLOGICA 48/2 – 2019 156 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST of the terra rossa type. Our hypothesis was tested with mineralogical, pollen, malacofauna, and paleomagnetic analyses of the sediments. We were also interested in the age and paleoenvironmental conditions of the terra rossa origin and the grey laminated sediments’ deposition. GEOGRAPHY & GEOLOGICAL SETTING The Dolenjska region covers the area between the Lju- bljana and Krško Basins (Fig. 1). It belongs to the most northeastern margin of the Dinaric Karst and is rich in karst forms (karren fields, dry valleys, dolines and shal- low uvalas). Relatively smooth un-dissected slopes of elongated hills point to vertical underground drainage. Although horizontal caves are almost absent, open shafts in the bottom of depressions below relatively thick clayey soils (so-called hidden shafts: Klimchouk et al. 1996) may indicate significant subsurface karstification. Main- ly low-energy relief has been developed on tectonically highly deformed Mesozoic carbonate (predominantly Jurassic and Triassic) and clastic successions (mainly Up- per Cretaceous to Early Eocene “flyshoid” sequences); see Fig. 3. Miocene (not in the nearby area) or younger overlying formations are separated from Mesozoic rocks with disconformities. The distribution and thickness of Cenozoic formations varies substantially over the area. So-called Plio-Quaternary deposits of the Dolenjska region represent a mapping unit in different geological maps (i.e., sheet Novo mesto: Pleničar et al. 1977; Slovene soil map: Grčman et al. 2015). They commonly overlay Miocene and also localized Pliocene deposits of Ter- tiary Basins (Krško, Kočevje and Kanižarica) and their surroundings. Plio-Quaternary layers consist mostly of reddish and brownish (locally also greyish) fine-grained siliciclastics and red soils. They may directly cover dif- ferent Mesozoic formations in a non-uniform and up to 10 km wide lowland corridor between Ljubljana and Krško Basins (so-called covered karst of Dolenjska; Fig. 1). There, the Plio-Quaternary deposits have never been directly dated. Unclear stratigraphic interpretation is based only on the comparison with more or less simi- lar deposits overlying Miocene or Pliocene sequences in both above mentioned Tertiary Basins. The thickness of Neogene and Quaternary depos- its may exceed 2,000 m in the central part of the Krško Basin syncline (Poljak & Gosar 2001; Gosar et al. 2005). So-called Plio-Quaternary red and brown loam is only preserved in patches in other parts of the low karst of Dolenjska (Buser 1974; Markič 2009). While some re- searchers considered red clays to be a type of freshwater deposit (Buser 1974; Pleničar & Premru 1977), the others described them as in situ or partly re-deposited weather- ing products on carbonate rocks (Gregorič 1969; Gams 2004; Rejšek et al. 2012). The studied sediment section near Karteljevo village (Fig. 3) was located in a karst doline over a hundred meters wide and more than 10 m deep (Fig. 2). It was situated at 315–320 m a. s. l. on a wider elevated surface above the Bršljinski potok valley and some 160 m above the river Krka in the Krško Basin at highway profile No. 104. Hills above the levelled surface with elevations of about 500 m a. s. l. represent a catchment area of smaller perennial brooks flowing in the direction of the excavated doline. The doline was formed in the Late Jurassic massive coarse- grained bioclastic limestone (Otoničar et al. 2006). In the area, the Mesozoic carbonate successions are overlain by Upper Cretaceous to Early Eocene “flyshoid” sequences (Fig. 3). The area belongs to the easternmost part of ex- tended Hrušica Nape (Placer 1999a) and represents part of the post-Miocene Sava compressional wedge close to its southwestern margin defined by the Stična Fault zone, a part of the Idrija tectonic zone (Placer 1999b). HRASTJE SEDIMENT SECTION The excavated sediment section on highway profile No. 104 (HP 104) in the bottom part of the doline was sam- pled in a thickness of 383 cm (Figs. 4, 6). It was composed principally of two parts: brownish yellow and grey which was which was separated by rubified transitional zone (Fig. 4a). The upper part (Fig. 4c) consisted mostly of clays and silty clays with interbeds, bands and laminas of clay- ey silts and sands. Sediments were predominantly grey with transitions to greenish-grey, sometimes with brown and beige mottles and yellowish-brown laminas. Some laminas and bands were several millimetres to rarely ACTA CARSOLOGICA 48/2 – 2019 157 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK more than a centimetre thick and mostly yellowish- brown stained. The transitional zone between lower and upper grey sediments was rubified; that part of the sec- tion consisted of predominantly homogenous grey clay, with localizedreddish to brownish mottles and periodical intercalations of brownish-yellow silt and sandy silt (Fig. 4a, c). The sediments are not accessible anymore because the motorway road-cut is sealed with a concrete wall and a tunnel was built. MATERIAL AND METHODS Sediments were macroscopically described and sampled in the field. The methods for more detailed studies and analyses performed on the samples are listed methods below. Paleomagnetic properties of 34 in situ oriented samples were analysed in the Department of Paleomag- netism, Czech Acad Sci, Inst Geol in Průhonice. The natural remanent magnetization (NRM) of sediments was measured using a JR-5A spinner magnetometer and the magnetic susceptibility (MS) of specimens was deter- mined using a KLY-4 Kappabridge (Jelínek 1966, 1973). The alternating field demagnetization (AF) by LDA–3A demagnetizer gave consistently good results. All samples were subjected to detailed AF in 14 steps. Data were ex- amined using vector endpoint or Zijderveld plots and M/ M n versus laboratory AF demagnetization fields. Individ- ual components of magnetization were determined using principal component analysis (Kirschvink 1980) for each sample. The A-component is undoubtedly of viscous ori- gin and can be demagnetized in the AF field (0–5 up to 10 mT). The characteristic high-field component (Ch- HFC) is stable and can be demagnetized or isolated in the AF field (ca 10–80 up to100 mT). For detailed procedure descriptions see Zupan Hajna et al. (2008). Standard zoopaleontological procedures were used to determine gastropod shells from the lower part of the section. The nomenclature and systematics follows Rie- del (1983) and Welter-Schultes (2012). Paleoenviron- mental characteristics follow Ložek (1964, 2000) and Alexandrowicz (1987). Fig. 4: Hrastje section at HP 104 covered by anthropogenic material from highway construction. Photo of a – studied grey sediments; b – bottom part of the section (grey sediments overlie brownish-yellow sediments), with location of plastic cubes of paleomagnetic samples; c – upper part of the section (grey sediments with rubified part). The lower part of the section (Fig. 4b) consisted of brownish-yellow clay to silt. Laminas were continuous or discontinuous and may show gradation and scour marks of mil- limetre scale. A mottled horizon between samples HL32 and HL33 contained plant remains and gas- tropods. Ferruginous coatings after root casts occured only close to the bottom of the section. ACTA CARSOLOGICA 48/2 – 2019 158 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST The MS U-series dating of gastropod shells failed due to technical problems with the counter in the labora- tory at University of Bergen, Norway. Samples for pollen analyses were prepared accord- ing to standard laboratory procedures (Fægri & Iversen 1989). The mineralogical composition was determined by powder X-ray diffraction (XRD). All powder pat- terns were collected with a Philips X´Pert APD diffrac- tometer (Department of Analytical Methods, Czech Acad Sci, Inst Geol in Praha) by standard procedures for randomly-oriented material, oriented specimens, glyco- lated specimens and the oriented samples heated to 400 °C under ambient atmosphere. For all samples, a region involving 060 reflection of clayey and micaceous miner- als was scanned. All diffraction patterns were taken in the continuous scanning mode with scanning speed of 1°min -1 in the angular range 2–75° 2 Θ. RESULTS PALEOMAGNETIC AND PETROMAGNETIC RESULTS Sediments are characterized by the NRM intensi- ties between 2.9 and 27 mA.m -1 and the MS values from 101 to 494 x 10 -6 SI units. Only the bottom sample HL34 (reverse polarized) is characterized by high values for both of the NRM (1,973 mA.m -1 ) and MS (5,060 x 10 -6 SI units). The mean direction and associated dispersion parameters of the Ch-HFC components with N polarity were calculated using Fisher statistics (Fisher 1953). The stereographic projection of the Ch-HFC with N polar- ity from is shown on Fig. 5. The mean paleomagnetic directions of these components for the normal polarity are declination (D) = 4.4°, inclination (I) = 46.5° (Tab. 1). Samples HL01, HL02, HL09, HL31 to HL33 were not used for the multi-component analysis as MAD values were higher than 6 (i.e., than the recommended value). Paleomagnetic directions for the sample with reverse po- larity are: D = 212°, I = -40°. The systematic acquisition of paleomagnetic data allowed the construction of a de- tailed magnetostratigraphic section (Fig. 6). Tab. 1: Mean paleomagnetic directions of samples (recalculated from Zupan Hajna et al. 2008, p. 202). Explanations: N – normal polarity; D, I – declination and inclination of the remanent magnetization after dip correction; α 95 – semi-vertical angle of the cone of confidence calculated according to Fischer (1953) at the 95% probability level; k – precision parameter; n – number of analyzed samples. Polarity Mean paleomagnetic Directions α 95 [o] k n D [o] I [o] N 4.4 46.5 4.7 36.0 27 Fig. 5: Mean directions of the ChRM components with normal (full) and reverse (open) paleomagnetic polarity for the sample HL 34. Stereographic projection, full circles represent projection onto the lower hemisphere. The mean directions calculated according to Fisher (1953) are marked by a small cross across a circle; the confi- dence circle at the 95% probability level is circumscribed about the mean direction. ACTA CARSOLOGICA 48/2 – 2019 159 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK Fig. 6: Basic magnetic and paleomagnetic properties of Hrastje section (same as HP 104 on Fig. 3). Black – N polarity, white – reverse po- larity, MS – the MS of samples in natural state, NRM – the modulus of the NRM, D – declination, I – inclination (modified from Zupan Hajna et al. 2008, p. 203). ACTA CARSOLOGICA 48/2 – 2019 160 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST GASTROPODS Few gastropod shells were found between samples HL32 and HL33 (Fig. 7), i.e., from the lower part of the doline fill. Two shells were partly broken in apertural segments. Only 3 specimens were collected directly from the sec- tion by macroscopic separation. The determination confirmed the following taxa and species (Fig. 7): • Specimen 1 – Aegopinella cf. minor (Stabile 1864), family Zonitidae (Fig. 7/1–5), adult individual with typically developed compressed round shell of 4.5 whorls. Conchological features indicate species be- longing to Aegopinella minor. The species of genus Aegopinella can be very similar, especially species Ae- gopinella minor and A. nitens. Accurate determination also requires a genital autopsy, which was not possible in this case. Our individual of Aegopinella belongs to A. minor with very high probability. • Specimen 2 – Vallonia pulchella (O. F. Müller, 1774), family Vallonidae (Fig. 7/6–10), a subadult individ- ual without developed peristome, but typically com- pressed round shell of 3 whorls. • Specimen 3 – Hygromiidae gen. et sp. indet. (Fig. 7/11–15), a subadult individual with a fragmented Fig. 7: Gastropod photos from sam- ple HL32 and HL33in different po- sitions. 1–5 Aegopinella cf. minor (Stabile 1864), view: 1 – detailed apical, 2 – apical, 3 – umbilical, 4 – apertural, 5 – abapertural; 6–10 Vallonia pulchella (O. F. Müller, 1774), view: 6 – detailed apical, 7 – apical, 8 – umbilical, 9 – apertural, 10 – abapertural; 11–15 Hygromii- dae gen. et sp. indet., view: 11 – de- tailed apical, 12 – apical, 13 – um- bilical, 14 – lateral, 15 – apertural (Photo: Oleg Mandić). Scale bars: 0.1 mm = 1, 6, 11; 1 mm = 2-5,7- 10,12-15. ACTA CARSOLOGICA 48/2 – 2019 161 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK shell in the apertural part. The shell has 4.5 whorls which indicate a subadult individual in this case. The shell surface has no preserved special determination characteristics to allow more generic or even species classification. On the basis of shell measurement, this individual is a medium-sized member of family Hy- gromiidae which is one of the richest European gas- tropod families with a high number of species. PALYNOLOGY We analysed 11 pollen samples (Tab. 2). Four samples (HL24, HL26–HL29, HL32–HL34 and HL33–HL34 were taken from the paleomagnetic section at the high- way profile No. 104 (Fig. 3). Five samples, roughly strati- graphically parallel to the lower part of paleomagnetic section, were sampled for comparison from the same filled doline at nearby highway profile No. 105 (Fig. 3). One additional sample was taken from the lower part of the filled doline containing the paleomagnetic section. Another sample represents wooden particles collected randomly in the lower part of the same doline. These ad- ditional samples were collected as sources of the addi- tional information when the paleomagnetic section (No. 104) was already destroyed. Each sample related to the paleomagnetic section comprises composite material taken between quoted pa- leomagnetic samples. Although we examined numerous microscopic slides, usually not more than a few to a few tens of pollen grains occurred per slide, with the excep- tions of the sample HL26–29 with almost 400 grains, and partly also HL24. Due to the generally scarce pollen con- tent, the results are presented in table (Tab. 2) are shown as numerical values of pollen grains and not as composite palynological graphs. Tab. 2: Palynospectra of the section Hrastje or profile HP104 and HP105 Filled karst doline Highway section No. 105 No. 104 Sample No. wood rem. lower pt. 8b 8a 7 3 1 34-33 34-32 29-26 24 Pinus 3 1 1 6 Picea 19 5 Abies 1 28 2 Juniperus 1 1 Taxus 1 Ephedra 1 1 Betula 3 3 3 43 2 Alnus 19 18 2 1 1 5 41 11 Corylus 33 10 Carpinus 17 1 Fagus 1? wood 83 1 Carya 1 Ulmus 1 1 1 Quercus 3 3 Tilia 1 1 Castanea 1 Juglans 4 Artemisia 1 Gramineae 1 12 1 Umbeliferae 1 2 1 6 3 Chenopodiaceae 2 Caryophyllaceae 3 Compositae-tub. 1 7 1 1 16 4 Compositae-lig. 2 1 1 5 1 Plantago 4 Cyperaceae 1 2 2 Myriophyllum 1 Sporae monol. 32 11 13 9 1 13 74 27 13 Sporae tril. 5 1 5 2 2 17 3 Selagimella 1 ACTA CARSOLOGICA 48/2 – 2019 162 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST Among pollen grains, tree species (AP) predomi- nated, while pollen grains of herbaceous vegetation (NAP) are less common. Abies pollen grains prevail among the coniferous vegetation (ca 8.3 %); Picea is less abundant (ca 5.7 %), while Pinus is much less abundant. Betula (ca 12.8 %), Alnus (ca 12.2 %), Corylus (ca 9.8 %) and Carpinus (ca 5 %) prevail among deciduous vegeta- tion, while Quercetum mixtum (Quercus, Tilia, Ulmus) was scarcely present. By contrast, Fagus pollens are very abundant (ca 24.8 %). Pollen grains of Castanea, Juglans, Taxus and water plant Myriophyllum occurred sporadi- cally. Remnants of wood with anatomical characteristics of beech (Fagus) were identified in the lower part of the section (sample HL32–34). MINERALOGY Sediment samples (HL08, HL19, HL23 and HL33) were collected from the Hrastje section (the paleomagnetic section) at highway profile No. 104 (Fig. 3). Reddish and grey clays (SLO 36 to SLO 38) were sampled from the same depression (at highway profile No. 105), but at the edge of the grey sediments towards the doline slope. A sample of red soil (SLO 7) was taken from highway profile No. 135 about one km from the studied profile. Two comparative samples (SLO 35 and SLO 39) were taken from two sites at highway construction some four kilometres away from the studied doline at highway profile No. 279. The mineralogical composition was in - ferred from patterns acquired from randomly-oriented, oriented, glycolated and heated specimens. Major and minor constituents of each sample are summarized in Tab. 3. Quartz with muscovite and chlorite dominated in almost all analysed samples (HL08, HL19, HL23, HL33) from the studied Hrastje section (profile No. 104); in all of those samples feldspars were also present. Prevail- ing chlorite with some goethite, muscovite and chlorite admixture was detected in red clay (SLO 36, profile No. 105). Calcite was associated with traces of randomly- interstratified structures of chlorite-muscovite type in green clay from dolomite (SLO 35, profile No. 279 on Fig 3). Kaolinite and montmorillonite prevailed with hema- tite in traces in red soil sample (SLO 7). Mineralogical composition of grey laminated sedi- ments which were slightly coloured were more or less equal (with differing quantities of quartz, chlorite, mus- covite, feldspar); only the pigmentation varied vertically and horizontally along the section. In red soil, the min- eralogical composition was different, since kaolinite and quartz predominated. Tab. 3: Sample lithology and results of XRD mineral identification (major phases in bold; completed from Bosák et al. 2006) of samples from highway profiles HP104, HP105, HP135 and HP279. Explanation: *as well as scans over region corresponding to 060 reflection of clayey and micaceous minerals; bold – dominating mineral; profile – number of highway profile; pink coloured cells – red soil sample. Sample Number ( HL = paleomagnetic sample) Lithology Mineralogical composition randomly oriented samples oriented, glycolated, and heated samples* mineralogical composition interstratified structures HL 8 profile 104 grey clay with brown and beige mottles quartz, muscovite, chlorite, feldspar quartz, muscovite, chlorite, feldspar chlorite-muscovite HL19 profile 104 brown sandy silt quartz, muscovite, chlorite, feldspar quartz, muscovite, chlorite chlorite-muscovite HL 23 profile 104 grey clay quartz, muscovite, chlorite, feldspar quartz, muscovite, chlorite, feldspar chlorite-muscovite HL 33 profile 104 brown-yellow silt with orange spots quartz, muscovite, chlorite, feldspar quartz, muscovite, chlorite chlorite-muscovite SLO 36 profile 105 reddish clay chlorite, goethite muscovite, chlorite none SLO 37 profile 105 greyish-brown clay quartz, muscovite, chlorite, feldspar quartz, muscovite, chlorite chlorite-muscovite SLO 38 profile 105 grey silt with white spots quartz, muscovite, chlorite, calcite, feldspar quartz, muscovite, chlorite chlorite-muscovite SLO 7 profile 135 red soil kaolinite, montmorillonite muscovite, illite, hematite montmorillonite- muscovite SLO 39 profile 279 laminated brown clay with thin yellow laminas quartz, calcite, muscovite, chlorite, feldspar quartz, muscovite, chlorite chlorite-muscovite SLO 35 profile 279 green clay in sandy dolomite calcite, dolomite, muscovite quartz, muscovite, calcite, ?kaolinite, ?illite none ACTA CARSOLOGICA 48/2 – 2019 163 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK DISCUSSION AND PALEOENVIRONMENTAL RESULTS The studied site and sedimentary successions in the Krško Basin cannot be directly correlated although they are geographically situated quite close to each other. The Krško Basin is a rather large tectonic depression with the character of a still active compressing syncline filled by over 2000 m of Neogene and Quaternary depositional se- quence (Poljak & Gosar 2001; Gosar et al. 2005) while the studied site represents a rather limited depositional area on karst relief. The Quaternary succession of the Krško Basin is built of interglacial, mainly fine-grained clas- tics of local alluvial input. They are disturbed by coarse- grained clastics of the river Sava, representing peaks of glacial periods and mainly deglaciation pulses (Verbič 2004). The wider surroundings of the Krško Basin, in- cluding the studied site, have been tectonically very ac- tive throughout the whole Quaternary (e.g., Verbič 2004; Vrabec & Fodor 2006). For example, the vertical com- ponent of the activity of the Artiče Fault is up to 15 m for the last 150 ka and up to 240 m for the last 1 to 2 Ma (Verbič 2004). PALEOMAGNETISM AND MAGNETOSTRATIGRAPHY Determined principal magnetic polarity directions were compared with the standard geomagnetic polarity time scale (GPTS; Cande & Kent 1995). Except for the last sample with reverse polarization at the bottom of the sampled section, all other samples show normal polari- zation. The mean paleomagnetic direction, derived from well-grouped vectors representing normal polarity, gave the evidence for probably clockwise rotation. If we con- sider the declination of 2.6° (at the time of sampling), then a clockwise rotation value is 1.8° ± 4.7°. Precise evaluation of paleomagnetic parameters indicates the geomagnetic excursion is unambiguous; we assume it is Blake excursion within the Brunhes chron. The character of D and I corresponds to zero Late Pleistocene and Holocene surface tilt of terraces within nearby Krško Basin. Verbič (2004, 2005) described di- minishing inclination of so-called Plio-Quaternary to Middle Pleistocene terrace surfaces in the direction of the pre-Quaternary Krško syncline axis. Geodetic obser- vations indicate ongoing folding within the Krško Basin (Poljak et al. 2010), which is not the case of the Hrastje section according to paleomagnetic parameters. Bavec et al. (2011) noticed these geodetic observations are with- out exception within the measurement error. Higher MS and NRM values in samples HL22, HL25 to HL28 and HL30 to HL32 above the paleosol horizon correspond to later rubification processes (reddish- to yellowish-brown lamination, mottling and staining). The MS and NRM values in samples below the protosol hori- zon are higher; in the reverse polarized sample HL34 for two orders higher than in samples above paleosol (NRM: 1,973 mA.m -1 ; MS: 5,060 x10 -6 SI units). Based on D and I values, we assume that there are not sufficiently centred paleosecular variations and de- position velocity might be relatively very high. GASTROPODS The terrestrial snail specimens record informative value about different paleoenvironmental conditions. Vallonia pulchella is a typical member of malacocoenoses of xerotermic habitats. This species prefers open ground habitats and avoids closed forests; thus the species is a typical heliophilous element. The occurrence of this spe- cies indicates the presence of some type of open ground habitat, probably in the form of small patches. Glacial environments are excluded, owing to type sediment in which the shell was preserved. Aegopinella cf. minor is a species of warm light forests, but not humid environ- ments. It belongs to ecological group 2W(s) (after Ložek 1964, 2000; Alexandrowicz 1987), which associates spe- cies with an affinity for sparse forests and semidry wood- land with semidry habitats. The species is a typical rep- resentative of the warm phases of Quaternary climatic cycle. The specimen determined as a taxon of family Hygromiidae has no outstanding indicator value. On the basis of shell shape, we could exclude some taxa of xero- termophilous elements such as genus Xerolenta, Helicella, Helicopsis, and Monacha. The shell shape appears to be similar to those of some species of genus Monachoides or Hygromia, but we lack specific determination character on the shell surface. PALYNOLOGY The lower part of the section (“lower part” and HL33–34; Tab. 2) contains only Sporae monol., rare Sporae tril. and Fagus wood. The material of sample HL34–32 represents a mixture of material from above and below the paleo- surface with protosol. Relatively poor palynospectra in the upper part of the section (samples HL24 and HL26–29; Tab. 2) suggest that during the sedimentation, the dominant cover of the landscape surrounding the investigated section was most likely riparian forest of temperate climatic zone. Several genera present (i.e., Myriophyllum and Cyperaeceae) in- dicate a quite humid environment (wetlands and ponds on periodically flooded plains). The relative scarcity of palynospectra (except one cumulative sample) could also result from quite rapid deposition of the grey laminated sediments, which means that the chance for pollen to be ACTA CARSOLOGICA 48/2 – 2019 164 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST trapped in our sediment decreases with the species abun- dance. It does not mean that species/genera not recorded in our spectra did not occur in original plant assemblag- es. The other possibility is that the lake had an outflow and flowing water transported pollen grains out of the depocenter. The chronological determination is rather uncertain as pollen analyses cover only a part of the sedimentary sequence. However, the determined vegetation could be placed in the Late Pleistocene with a high degree of cer- tainty. Unfortunately, sections with Late Pleistocene veg- etation are scarce in Slovenia. Two cores over 100 m deep were palynologically analyzed and determined in the Lju- bljana Moor (Šercelj 1965, 1966). There, the interglacial (Eemian, i.e., MIS 5e) as well as interstadial (MIS 5c of Last Glacial) determined vegetation is comparable with our site. The high percentage of beech pollen in our samples indicates rather interglacial conditions. Although beech was already present in the Ljubljana Moore at that time, it was not as abundant as in our samples. However, Pinus was more common in the Ljubljana Moore but its curve in pollen diagram is oscillates. Pollen of Taxus, Carya and Tsuga is still present sporadically, while in all our samples only one grain of Taxus and one of Carya have been found. Elements of Tegelen-type of flora gradually disappeared from the Pleistocene vegetation, although south of Alps it persisted longer than in the regions north of them, even into the Late Weichselian (Šercelj 1965). Pollen from sample HL26–29 are comparable with certain segments of the pollen diagrams from the Mond- see (near Salzburg City, Austria, northern Alpine foot- hills; Drescher-Schneider 2000) correlated with MIS 5c (see Pini et al. 2009), but elements of Tegelen-type of flo- ra as well as beech pollen are missing there. In contrast, the Eemian interglacial vegetation from Central Italy comparable with our samples still contains abundant ele- ments of the Tegelen-type flora, i.e., Pterocarya and Zel- kova, as well as beech pollen (Follieri & Magri 2001). Ac- cording to comparison with Zuzano Decimo core (plain of Friuli, NE Italy, close to Dinaric Karst) where pollen of thermophilous trees and shrubs (deciduous Quercus, Corylus, Ulmus, Tilia, Carpinus) dominates while the fre- quency of Fagus pollen is low (Pini et al. 2009), we can also correlate Hrastje section with MIS 5e. They stated that the continuous record of Fagus, although with low percentage values, is unprecedented in classical Eemian equivalents in the Alpine region. Magri et al. (2006) and Pini et al. (2009) connected post-Eemian Fagus expan- sion at many European sites to MIS 5c (at ca 105–95 ka) when becoming quite abundant in Italian and Balkan peninsulas, and also across the Alps. The closest dated clayey material somewhat similar to the studied section is documented from a clay pit at the brick factory few kilometres to the west from Novo mesto. There, the Cromerian interglacial and one of the Menapian interstadials were reported from the lower part of the section where the Tegelen-type of vegetation was determined with a remark that even older Pleisto- cene ages are not excluded (Šercelj 1961a, b, 1963). The upper horizon of the pit includes pollen typical for glacial periods, most probably from the last Weichselian colder stage (Šercelj 1963). MINERALOGICAL COMPOSITION AND ITS ORIGIN Clay minerals in soils and clastic (e.g., alluvial) sediments represent products of dynamic systems that are strongly affected by time-influenced changes of environment when they originated (deposition, weathering, pedo- genesis). Main components of studied sediments are not representative of clay minerals or iron oxides related to intensive weathering, i.e., sediments were not subjected to intensive weathering/pedogenesis before and especial- ly after the deposition; the sediments are not too mature (plagioclases and muscovite are still present). The min- eralogical composition of nearly all samples is similar in general with the exception of the mineralogical composi- tion of red soil sample. In a paleogeographic sense, the wider surround- ings of the studied area belong to the eastern marginal parts of Adriatic carbonate platform (Jurassic and Cre- taceous) and its slope towards the Slovenian Basin. The area was uplifted, subaerially exposed, tectonically dis- sected, denuded, and karstified after the Paleogene. It is evident that the studied clayey material was deposited over already well-expressed karst relief (Fig. 2), devel- oped after the erosion of Cretaceous to Early Eocene “flyschoid” deposits overlying older carbonate sequences (see Crnjaković 1981). Nevertheless, the erosion relics of “flyschoid” deposits still occur in the area; the closest ones are just a few hundred meters from the studied site (Otoničar et al. 2006; Fig. 3). Plagioclases do not represent insoluble remains of limestone as their amounts were not determined in re- spective weathering products of Cretaceous and Juras- sic limestones of the Dolenjska region. The plagioclase source can be found in re-deposited weathering residua of non-carbonate rocks or some other type of sedimen- tary cover (Habič 1992; Zupan Hajna 1992). Patches of similar reddish-brown, reddish and yellowish loamy to sandy deposits were also found west from the studied section in the Suha Krajina but in slightly higher alti- tudes. The origin of grey alluvial, lacustrine or/and pa- ludal laminated sediments can be specified from the mineralogical composition only conditionally. We can ACTA CARSOLOGICA 48/2 – 2019 165 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK exclude the in situ weathering of local carbonate rocks, except in the case of sample SLO 35 (weathered dolomite with green clay) which is not directly connected with the studied site. The main source of grey sediment can be related to non-carbonate rocks from the vicinity, i.e., Cretaceous to Early Eocene “flyschoid” deposits or older alluvial sediments from various locations on the Dolen- jska Karst (Zupan Hajna 1992). We suggest that parent material, composed of Late Cretaceous flyschoid marls, clayey limestones and calcarenites with different amount of clayey materials and quartz grains, was eroded from the upper parts of nearby hills (Fig. 3) and transported down slopes to a karstified surface already covered by red soils. The transitions from grey and brownish-grey (co- loured by goethite pigment) through the mottled horizon to reddish-brown sediments (coloured by hematite pig- ment) indicates the effects of rubification. It is influenced by meteoric waters percolating through deposits after their deposition and reflects the redox potential change (from the reduction to oxidation environment; Mihevc & Zupan Hajna 1996). The rubification penetrates into the sediment and forms red clay coatings. Goethite (sample SLO 36) and hematite apparently represent just the pig- ment (coating over other mineral particles) in amount so low that they cannot be detected even in traces in XRD records of reddish samples. Heavy mineral assemblages in trace amounts cannot be detected by the XRD as well. The reddish clay (SLO 36, profile 105) and grey laminated sediment of the Hrastje section (profile 104) differ in mineralogical composition from red soil mate- rial (sample SLO 7, profile 135). The red soil contains kaolinite and montmorillonite, interstratified structures of illite and montmorillonite-muscovite type of clay min- erals as the main components, which indicate strong or long-lasting weathering, but no quartz, chlorite and feld- spar. Red soil (SLO 7) can be classified as typical red soils (i.e., terra rossa) which are known along Dinaric Karst and in the whole Mediterranean region as well (Fedoroff & Courty 2014). The literature does not provide much information about the duration of the rubification–il- luviation phase of red Mediterranean soils (RMSs; see Fedoroff & Courty 2014). Based on the high number of microlamination and the thickness of the clay coatings and their abundance in the RMSs, the rubification–illu- viation process can be very fast, from 100 years to a few thousand years and it is believed that it is related to inter- glacials (e.g., Carboni et al. 2006; Zembo 2010), especial- ly their wet phases (Badía et al. 2009; Wagner et al. 2012). Different mineralogical compositions of red soil and grey laminated sediments which were partly rubified can easily indicate that grey sediments (1) are less weathered; (2) they have other source material provenience than red soils, and (3) they are younger than underlying red soil. In addition, the mineralogical study indicates that the source material of grey laminated sediments may derive Fig. 8: Schematic cross section of doline filled by red soil and lacustrine laminated sediments. Legend: 1 – Karstified Jurassic limestone; 2 – Well-developed red soil (terra rossa); 3 – Brownish-yellow clay to silt with plant remains and ferrugineous coatings; 4 – Partly rubified grey sediment containing mostly quartz, feldspars and chlorite; 5 – Rock debris; 6 – Wood, plants and gastropods; 7 – Studied section with magnetic polarity: black – normal polarity, white – reversal polarity. ACTA CARSOLOGICA 48/2 – 2019 166 LATE PLEISTOCENE LACUSTRINE SEDIMENTS AND THEIR RELATION TO RED SOILS IN THE NORTHEASTERN MARGIN OF THE DINARIC KARST from eroded nearby non-carbonate sedimentary rocks. The relation of grey laminated sediments and red soil and the karstified carbonate bedrock is shown on the sche- matic model in Fig. 8. It follows that the grey laminated sediments cannot represent the source material of Dolenjska red soils (i.e., terra rossa). Clear vertical and lateral colour changes from the central part towards marginal parts of studied sediments resulted from post-depositional changes, i.e., rubification. More distinct reddish- to yellowish-brown laminas in samples HL14 to HL24 indicate the transport of eroded and re-worked red-coloured sediments into grey sediments from nearby areas or in situ rubification on the lake floor, which correspond to higher MS a NRM values. Ochre to reddish staining and mottling is the re- sult of oxidation of iron minerals and formation of goe- thite and hematite pigments by the rubification process which is also responsible for increased MS a NRM values. Oxidizing meteoric waters have percolated more easily into sediments along bedrock/sediment contacts, than through impermeable clayey deposits in the central part of the doline, where overlaying strata sealed the doline fill and protected the central part of doline from the oxida- tion. Mostly sediments at the top of doline fill and in the border zone along the walls of depression where mete- oric water could reach them were partly rubified. Palynospectra with quite abundant Fagus indicate that the dominant landscape cover during sediment de- position was most likely forest with wetlands and ponds on periodically flooded plains. The Fagus abundance might indicate that the area was a part of the Eemian refuge (Magri et al. 2006; Brus 2010) at that time. The scarce palynospectra and not stabilized secular variation in grey laminated sediments can indicate a quite rapid depositional rate of grey laminated sediments. The doline represented a trap for siliciclastic material with a highly reduction environment at the bottom full of vegetation fragments and pieces. Yellowish- and reddish-brown mottling and staining mostly resulted from post-depo- sitional rubification processes responsible for increased MS and NRM values and probably represent inverted pseudogley. Paleosol horizon between samples HL32 and HL33 with plant remains, gastropods, and ferruginous coatings after root casts represents the important paleoenviron- mental and stratigraphic boundary (unconformity). The sediment is clayey silt, yellowish-brown in colour. Gas- tropod assemblages in the paleosol indicate the presence of open ground habitats, probably in the form of small patches within warm sparse forests and semidry wood- land. The species are typical representatives of Quater- nary warm phases. Palynological assemblages below the paleosol are highly impoverished, containing only lim- ited numbers of Sporae monol., rare Sporae tril. and frag- ments of Fagus wood. The lowest paleomagnetic sample shows reverse polarity of the magnetic field and in order higher MS and NRM values. If we accept the correlation of Hrastje palynospec- tra with those of the Mondsee site (Austria) and their radiometric dating (Pini et al. 2009), then the grey sedi- ments were deposited during MIS 5c (ca 105 to 85 ka BP; Railsback et al. 2015) and sediments below the paleosol horizon with reverse polarization of the last sample can correspond to the Blake excursion and consequently re- lates to MIS 5e. The Blake excursion was identified by Smith & Fos- ter (1969) for the first time. The age of the Blake event has been dated by different methods of numerical dating mostly from ca 120 to ca 111 ka (e.g., 111.8±1 to 117.1±1.2 ka: Zhu et al. 1994 from Chinese loess; 114.47 to 119.97 ka: Fang et al. 1997 from Chinese loess or 112.0±1.9 to 116.5±0.7 ka: Osete et al. 2012 in stalagmite). Dates ac- cording to applied dating methods (Singer 2014) vary from 130–124 ka (Bourne et al. 2010) up to 114–108 ka BP (Smith & Foster 1969) with event duration of ca 4 to 6 ka (according to different sources). The excursion con - sequently relates to MIS 5e, its late part, or to the vicin- ity of MIS 5e/5d boundary (cf. Singer 2014; Railsback et al. 2015). Its bipartite composition (Singer 2014) was not detected in our section. CONCLUSIONS The fill of a large karst depression (doline) was excavated during the construction of the Slovene highway No. A2 at section Hrastje – Lešnica in the Dolenjska region. The fill represents the youngest sedimentation of the site and overlies red soils (i.e., terra rossa). From the base up, the fill consists of: (1) brownish- yellow clays to silts locally with a few plant remains, fer- rugineous coatings after root casts and gastropods (pa- leosol horizon) contain chlorite, muscovite and feldspars are present in the bottom part. The mineralogical com- position shows no difference regarding upper part of the section except that there is more reddish stained and that was already partly changed due to pedogenesis (start of paleosoil formation). Strongly impoverished malacocoe- ACTA CARSOLOGICA 48/2 – 2019 167 NADJA ZUPAN HAJNA, BOJAN OTONIČAR, PETR PRUNER, METKA CULIBERG, JAROSLAV HLAV ÁČ, OLEG MANDIĆ, ROMAN SKÁLA & PAVEL BOSÁK nosis indicates only general paleoenvironmental charac- teristics, which are consistent with a warm phase of one of Quaternary climatic cycles with developed light, semi- open forest with patches of open ground habitats, i.e., paleoenvironmentally different conditions from those present during deposition of overlying grey sediments. The only paleomagnetic sample show reverse magnetiza- tion. The precise evaluation of paleomagnetic parameters indicates the geomagnetic excursion is unambiguous. W e assume it is the Blake excursion (ca. 120–112 ka; MIS 5e) rather than Brunhes/Matuyama boundary (0.78 Ma; MIS 19). (2) Lacustrine (palustrine) laminated grey to green- ish grey deposits dominated by quartz, muscovite, chlo- rite and feldspar with randomly interstratified structures of chlorite-muscovite type. The sediment is almost un- weathered (suggested by the content of feldspars, musco- vite and chlorite) but partly rubified at the contact with percolating water and older red soils. They were deposit- ed were deposited in a colder climate (low MS and NRM values) with reduction conditions at the lake bottom full of decomposing organic matter. The mineralogical composition of laminated grey sediments and underlying older terra rossa soils indicates that the grey sediments cannot serve as parent (source) material for terra rossa evolution of the area. Relatively poor palynospectra may have resulted from flowing wa- ter transporting pollen grains out of the depocentre and/ or rapid deposition of grey sediments (hence decreased opportunities for pollen to be trapped in sediment). The latter explanation is supported also by insufficiently cen- tered paleosecular variations. Plant assemblages indicate that the surrounding landscape was covered dominantly by temperate climatic zone riparian forest with some quite humid environments such as wetlands and ponds on a periodically flooded plain. The grey sediments could have been deposited during any warmer cycle in the Pleistocene. Nevertheless, the regional correlation, based especially on the abundance of Fagus, indicates deposi- tion at the very beginning of the last glacial cycle in its warmer oscillation MIS 5c (ca 105–95 ka). All samples show normal magnetization. The mean paleomagnetic direction derived from well-grouped vectors represent- ing normal polarity gave the evidence for probably slight clockwise rotation, which is less pronounced than in the nearby Krško Basin. With respect to correlation of palynospectra with sites in the northern Mediterranean and northern Alpine foothills and the character of paleomagnetic parameters, we can conclude that the brown-yellow sediments with a paleosol horizon are products of deposition during the Eemian interglacial (MIS 5e, ca 120–112 ka) while the overlying grey sediments were most probably deposited during start of the last glaciation (Würmian), i.e., during warmer oscillation MIS 5c (W1/ca 105–85 ka). Regarding mineralogical composition, the studied grey (partly rubified) laminated sediments have no rela- tion with the red soils (i.e., terra rossa) in the area; and they do not represent their parent (source) material. ACKNOWLEDGEMENTS The co-operation of Mr. Jiří Dobrovolný (XRD analyst), Dr. Maja Andrič, Dr. Jiřina Dašková and Maryna Komar, DSc. (palynology consultations) is highly acknowledged. The authors acknowledge the financial support from the Slovenian Research Agency (research core funding No. P6-0119). Analyses, processing and in- terpretation in the Czech Republic were carried out within the Research Plan of the Institute of Geology Acad Sci Czech Rep No. AV0Z30130516, Plan of the In- stitutional Financing of the Czech Acad Sci, Inst Geol No. RVO67985831, and Grants of the Grant Agency of the Academy of Sciences of the Czech Republic Nos. IAA3013201 (; IAA300130701 and Bilateral Mobility program of SAZU/Czech Acad Sci No. SAZU-16-03. Authors acknowledge fruitful comments of two review- ers for constructive suggestions and proposed correc- tions to improve the paper as well as Carolyn L. Ramsey for improving the use of English. 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