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Palaeoenvironmental reconstruction of the Ruma-brickyard section

Mladjen Jovanovic1, Ulrich Hambach2, Tivadar Gaudenyi3, Slobodan Markovic4, Martin Christoph5
1 Chair of Physical Geography, University of Novi Sad, Serbia
2 Chair of Geomorphology, University of Bayreuth
3 Geographical Institute "Jovan Cvijic", SASA, Belgrade, Serbia
4 LAPER, University of Novi Sad, Serbia
5 Bayreuth

P 2.4 in Löss und terrestrische Archive

 

The Ruma loess-paleosol section is situated in SE part of Carpathian basin, on the southern slopes of Fruska Gora Mnt (Crveni Cot, 538 m asl). In a local brickyard, loess-paleosol sequences (LPSS) are exposed in different levels along 1500 m of excavation front. The up to 20 m thick LPSS contain five fossil soils separated by six loess layers, which were formed during the late part of the Middle and during the Late Pleistocene.

As results of Late Pliocene and Early Quaternary accelerated uplifting of Fruska Gora Mtn. (recent rate up to 1 mm/y) and consequent erosion, a relatively thick succession of pre-loess polycyclic fluvial-lacustrine products were deposited in subsidential basins (recent rate -1 mm/y), whereas proluvial, proluvial-deluvial and marshy and sediments were laid at mountain’s slopes. Succeeding LPSS dips towards SSE at an angle of ~10o. In contrast of typical plateau loess from eastern part of Srem loess plateu (SLP), loess sediments from southern slopes of Fruska Gora Mnt. were recognized as „slope loess“ or “loess derivatives”. These LPSS were formed during a succession of events in any order: dust accumulation, pedogenesis and slope processes.

A set of samples (spacing 5 cm) for various rock-magnetic experiments was taken along 14.6 m of a single column. A detailed description of the section is the backbone for further interpretations. These data were combined with previously obtained results of magnetic susceptibility (MS), grain size, fossil land snail assemblage and AAR geochronology.

The oldest exposed soil V-S3 represents more than 2 m thick rubified Luvisol with strongly developed basal BC and C horizons with huge carbonate concretions and hydromorphic features. A boundary between V-S3 and V-L3 is mostly sharp as result of different kind of slope processes. Loess horizon V-L3 is also disturbed with many hydromorphic features and fossil root channels. Overlaying double Chernozeme pedocomplex V-S2S2 (120 cm thick) and V-S2S1 (100 cm) is interbedded with 80 cm of loess affected by pedogenesis. The typical and well separated V-S2 double-peak in the MS and the frequency dependent MS record is not recognized here.

A distinct orange-yellowish layer, 2 cm thick, with an extremely strong MS signal (275.6 x 10-8 m3kg-1) was recognized as tephra layer. The same layer was found in several LPSS in Carpathian basin and appears to have a minimum luminescence age of about 145 kyr. Unlike the others LPSS in Vojvodina, where this tephra layer is positioned in the middle or upper part of V-L2, in Ruma it is placed almost on the top of V-S2S1.

Last interglacial soil (V-S1), interstadial soil (V-L1S1) and recent soil (V-S0) show in some sections increased thickness. These features, previously described as crossections of paleodepresions (paleodolinas) were recently recognized as remains of a paleochannel system. The accumulation of loess-like slope sediments during the late MIS 6 was succeeded by the incision of channels rooting in the Fruska Gora Mtn. These periodical active channels were also suitable environment for formation of thick soil horizons. Aeolian influx was occasionally overcome with extensive accumulation of coluvial material. Not only pellet sands, but also decimeters size loess blocks were found in the soil. Despite proluvial erosion episodes, during which soils were flushed downstream, up to 6 m thick V-S1 were preserved. In contrast, on the gentle slopes between channels, only weak top A horizon remained. Such kind of soil formation process continues during V-L1S1 and V-S0 formation. On the satellite images of the area, a much denser paleochannel network than present one is noticeable.

The accumulation of Upper Pleistocene V-L1 layer occured during drier environmental conditions than older loess and paleosol units. The five paleosol horizons in the Ruma brickyard were formed in a very dynamic slope environment and represent the transition from humid forest conditions to relatively dry steppe interglacial landscapes during the last about 350 kyr.

 

Letzte Änderung 31.07.2012