Pleistocene to Holocene evolution of Bahluieț Valley at Costești (Iași County, Romania) – an interplay between fluvial and hillslope processes

Abstract

Bahluieț Valley at Costești Village (Moldavian Plateau, Romania) is an archaeosite and geosite of unique relevance for the geomorphological evolution of Moldavian Plateau in the Upper Pleistocene and the Holocene (Niculiță și Mărgărint, 2018; Niculiță, 2022). The Bahluieț valley sides are affected by generations of landslides, some of which are fossil. The landslided material accumulated in the floodplain that represents the fossil landslide was covered by alluvial deposits. The post-LGM incision dettached the coverlet of fluvial deposits as a terrace and exposed the fossil landslide in the bank of the active floodplain.

At the current stage of geomorphological research, the Late Pleistocene age of the fossil landslides is well constrained by the ages of the terrace, without the possibility of saying the precise moment of the trigger, but only the upper limits: 15 to 46 ky BP (Niculita, 2021). These limits imply that multiple events generated the deposit of fossil landslides (Niculita, 2021). This is also supported by the non-continuous outcrops from the banks of the active channel. The fossil landslides are rock slides, while the retrogressive reactivations that followed the initial landslides are various types of rotational and translational slides.