Recognition and interpretation of paleosols sequences in a floodplain from the low tableland of Transylvania Depression, Romania

Abstract

Palaeosols reflect quite accurately the paleogeographic conditions in which they formed and evolved. Many studies were focused on this target in different settings (lakes, loess plateaus and plains, floodplains and archaeological sites).

Here we present the palaeosols sequences in the floodplain of Partoț River, situated in the low tableland of Transylvania Depression. The observations were performed on three cores, one located at ca. 1 km downstream  from theȘtiucilorLake(profile no. 3) and the other two at 1 km (profile no. 1), respectively 4 km (profile no. 2), upstream from the lake.

The thickness of floodplain sediments is ca. 12 m upstream from Stiucilor Lake, and ca. 6 m downstream from this lake. In the bottom are present cobbles and pebbles, covered by 1-2 m thick sequence of fine and medium sands, followed by 5 to 10 m thick fine silty – clayey materials. The alluvial and lacustrine sediments suggest that the vertical aggradation was the main process on the surface of this floodplain.

The maximum age of fine silty-clayie sediments, indicate that this sedimentary sequence starts in Bolling – Allerod interstadial. A very low sedimentation rate characterised the first part of the sequence, as only ca. 1 m of materials seams to be accumulated between Bolling – Allerod interstadial and Mid Holocene.

After ca. 6000 yrs BP, when Stiucilor Lake has formed, the sedimentation rate increased dramatically, both  upstream and downstream from it. Upstream from the lake, the tickness of lacustrine/alluvial materials is ca. 9 to 10 m, while downstream, the sedimentation rate was slighlty reduced, and the thickness of fluvial/torrential sediments are of ca. 5 m.