Stable isotope study in a weakly developed paleosol horizon in the Quaternary Vár-hegy travertine (Budapest, Hungary)

Abstract

The intraformational paleosol and calcareous muddy cavity fills interbedded in the travertine of the Var-hegy (Castle Hill) in Budapest were analyzed for carbon and oxygen isotope compositions and compared with the isotope compositions of the host travertine. Microscopic investigations of these layers indicate mechanical reworking of the travertine and mixing with the allothigenic siliciclastic material. Micromorphological features, e.g. needle-fiber calcite, carbonate hypocoatings around pores, ferruginous precipitations and clay infillings in the paleosol and cavity fills indicate that in situ pedogenic processes were active in both layers. The presence of ferrihydrite in the A horizon of the paleosol also supports pedogenic alteration. The stable carbon and oxygen isotope compositions of bulk carbonate of paleosol and cavity fills (d13C= -0.6 to 2.1‰ and d 18O= -16.7 to -12.9‰) are very close to the compositions of the host travertine (d 13C=1.1 to 2.1‰ and d 18O = -17.7 to -13.7‰,) and differ from the...