Mineralogical, sedimentological and palaeoenvironmental study of Quaternary sediments from Ceglédbercel road cut, Hungary

Abstract

This study looks at the locality of Ceglédbercel and, using a process of detailed mapping and systematical sampling,
describes a 700m-long cut of the nearby road highway 4. The aim of this research was to obtain information about the loess
and other overlying sediments on the SW slope of the Kálvin Hill (191.5 m). More precisely, the aim was to examine the
mineralogy, the grain-size and distribution of loess particles, the pollen and gastropoda content, the 14C age and finally, marks
indicating the brittle deformation of sediments. The observations focused mainly on the loess-type deposits.
The three outcropping, slightly clayey loess levels (l1, l2 and l3) were separated by two buried, partly eroded palaeosoil levels (t1 and t2). The grain-size distribution of loess levels l1 and l3 demonstrated their aeolian character, while l2 level
illustrated the character of the mixed (aeolian-aquatic) sedimentation. By studying the variation coefficients of the grainsize distribution (as mean diameter Mz, dispersion σ, skewness Sk, and kurtois KG for several loess levels) it was possible
to ascertain that the dust was transported from the east; furthermore, the dust probably originated in barren, frostshattered Oligo-Miocene sediments, including their finest (clayey) grain-size fractions. Thus the ordered lattice of the
clay minerals of the loess may be explained by the “inherited” character of these minerals. At the same time, the
deposition of the loess seems to have taken place over a long period of time (especially in the case of level l3); it was also
apparent that the intensity of the deposition was relatively constant, as was the direction of dust-carrying winds.
Given the results of the palaeontological and geochronological data, the evidence suggests that the studied loess
column originated approximately 19,780 years ago. Furthermore, it continued to spread over the soil levels of Jászfelsőszentgyörgy (18,500 years ago) and Mende (19,780 years ago), until the last (W3) cold and dry period of the Pleistocene.
The post-glacial ice melting is marked by three coarse sand levels (h1, h2 and h3), while the upper, black soil which covers
the non-conforming surface of these sand levels (t3) was formed during the QC phase of the Early Holocene Climatic
Optimum. It is important to notice that the neo-tectonic, brittle deformations (i.e. the lime veins, “dry” joints and microfaults) stopped below the Holocene/Pleistocene boundary.