Late Pleistocene lacustrine sediments and their relation to red soils in the Northeastern margin of the Dinaric Karst

0520611 - GLÚ 2020 RIV SI eng J - Journal Article
Zupan Hajna, N. - Otoničar, B. - Pruner, Petr - Culiberg, M. - Hlaváč, Jaroslav - Mandić, O. - Skála, Roman - Bosák, Pavel
Late Pleistocene lacustrine sediments and their relation to red soils in the Northeastern margin of the Dinaric Karst.
Acta carsologica. Roč. 48, č. 2 (2019), s. 153-171. ISSN 0583-6050. E-ISSN 1580-2612
R&D Projects: GA AV ČR IAA300130701
Institutional support: RVO:67985831
Keywords : karst sediments * mineralogy * gastropods * palynology * paleomagnetism * paleoenvironment * Dolenjska region * Slovenia
OECD category: 1.5. Earth and related environmental sciences
Impact factor: 0.806, year: 2019
Method of publishing: Open access
https://ojs.zrc-sazu.si/carsologica/article/view/7080/7234

A large karst doline at section Hrastje – Lešnica in the Dolenjska 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 contains 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 Quaternary warm phase characterized by light semi-open forest with patches of open ground habitats. Only the last paleomagnetic sample in the bottom of sediment sequence shows reverse polarity of magnetic field and represents the geomagnetic excursion, 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 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 depression. The grey sediment has a different mineralogical composition 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 Mediterranean climatic conditions). Laminated grey sediment was deposited 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 surrounding landscape was temperate climatic zone riparian forest with some quite humid environment as wetlands and ponds on periodically flooded plain. The regional correlation, based especially 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 magnetization and negligible clockwise rotation of 1.8° ± 4.7°.
Permanent Link: http://hdl.handle.net/11104/0305380