Hidromorfne oblike v pliokvartarnih mokriščnih paleotleh na območju avtocestnega odseka Cogetinci – Vučja vas : magistrsko delo

Hartman, Jernej (author), Popit, Tomislav (mentor), Košir, Adrijan (co-mentor)

Med gradnjo avtocestnega odseka Cogetinci–Vučja Vas je bilo detajlno sedimentološko evidentiranih več deset metrov izpostavljenih profilov domnevno pliokvartarnih aluvialnih plasti. Z analizo granulometrijske ter mineraloške sestave, ter z ozirom na stratigrafijo, smo definirali sedimentacijsko okolje, nadalje pa smo z morfološko in elementno analizo prepoznali in opisali hidromorfne oblike ter razpravljali o njihovem nastanku. Sklepamo, da gre v našem primeru za del aluvialnega sistema, ki ga karakterizirajo relativno stabilna rečna korita z občasnimi razlivi čez obrežne nasipe oziroma s prebojem skoznje. Z oddaljevanjem od glavnega korita je naplavljanje počasno, a stabilno, v naplavinah pa se sistematično zmanjšuje velikost zrn, kar pogojuje nastanku razmeroma anaerobnih okolij. Posledično so se v proksimalnem delu glede na korito tvorila sestavljena tla s slabo izraženimi profili, z oddaljevanjem od korita pa so nastajali kumulativni profili. Kljub slabši razvitosti paleotal, na kar pričata skorajšnja odsotnost talnih horizontov in ohranjena sedimentološka stratifikacija, ta kažejo redoksimorfne oblike, ki jih uporabimo za identifikacijo mokriščnih tal. Nastanejo z redukcijo železovih (Fe) in manganovih (Mn) oksidov in hidroksidov, ki so nato transportirani in reoksidirani v območjih kjer je prisoten kisik. Ločimo tri kategorije redoksimorfnih oblik, ki jih povzemamo iz tuje literature in smo jim nadeli slovensko terminologijo, in sicer: a) redoks osiromašenje, b) redoks obogatitev in c) reducirana osnova. Pri psevdogleju, ki karakterizira obravnavana paleotla, ta večino leta niso bila zasičena z vodo. Voda je občasno stagnirala v slabo prepustnih plasteh zgornjega dela paleotalnega profila, zaradi česar so bile te reducirane, Fe in Mn pa sta se pomikala proti prezračenim koreninskim kanalom kjer sta oksidirala. Skozi bolj prepustne plasti v spodjih delih profila je voda iskala pot v večjih makroporah oziroma koreninskih kanalih in jih reducirala, tok vode pa ni vplival na osnovo, ki je ostala oksidirana in je akumulirala še več Fe, Mn in gline, ko so ti prodirali skoznjo.

• Language: Slovenian
• Keywords: sedimentologija, paleopedologija, hidromorfne oblike, redoksimorfne oblike, pliokvartar
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: J. Hartman
• Year: 2024
• Number of pages: XIV, 91 str.
• PID: 20.500.12556/RUL-154884
• UDC: 55
• COBISS.SI-ID: 188493571
• Publication date in RUL: 07.03.2024

Secondary language

• Language: English
• Title: Hydromorphic features of Plio-Quarternary wetland paleosoils in area of motorway section Cogetinci – Vučja vas : master's thesis

Abstract

During the construction of the Cogetinci-Vučja Vas highway section, tens of meters of exposed profiles of presumably Plio-Quaternary alluvial layers were recorded in detail. By analyzing the granulometric and mineralogical composition and considering the stratigraphy, we defined the sedimentation environment, furthermore, by morphological and elemental analysis, we identified and described hydromorphic features and discussed their origin. We conclude that the studied case defines a part of the alluvial system, which is characterized by relatively stable riverbeds with occasional spills over the embankments or by breaking through them. With distance from the main channel, deposition is slow but stable, and alluvium systematically thins and decreases in grain size, which favours the formation of relatively anaerobic environments. As a result, composite soils with poorly defined profiles are formed proximal to main channel, while cumulative profiles are formed in the distal part. Despite the poor development of paleosols, as evidenced by the near absence of soil horizons and by preserved sedimentological stratification, they contain redoximorphic features that are used to identify wetland soils. They are formed by the reduction of iron (Fe) and manganese (Mn) oxides and hydroxides, which are then transported and reoxidized in areas where oxygen is present. We distinguish three categories of redoximorphic features, which are taken from foreign literature and given Slovenian terminology, namely: a) redox concentration, b) redox depletion and c) reduced matrix. In the case of surface water gley, which characterizes the studied paleosoils, these were not saturated with water for most of the year. Water occasionally stagnated in the poorly permeable layers of the upper part of the paleosoil profile, as a result of which they were reduced, and Fe/Mn moved towards the aerated root channels where they oxidized. Through the more permeable layers in the lower parts of the profile, water found its way in the larger macropores or root channels and reduced area around them, but the water flow did not affect the soil matrix, which remained oxidized and accumulated even more Fe, Mn and clay as they penetrated through.

• Keywords: sedimentology, paleopedology, hydromorphic features, redoximorphic features, plio-quarternary