Stable isotope geochemistry of Pleistocene travertine from Budakalász (Buda Mts, Hungary)

Abstract

In the Buda Mts. (Hungary) several Pleistocene travertine outcrops are known. The subject of this paper is a stable isotope study on the Pleistocene travertine from Budakalász that was deposited on the slope of Monalovác Hill of the Buda Mts. The principal goal of this work is to define the depositional environment and related implications by studying the petrographical and microfacies features and C and O stable isotope compositions. The Budakalász travertine can be divided into two stratigraphic units. The lower part of the studied sections (approx. 15 m thick) consists of massive limestone, which represents a "smooth-slope" facies and has mean d13C and d18O values of 2.21‰ and -11.1‰ relative to V-PDB, respectively. Microbial shrub structures were also recognized in the lower part of the section, showing slightly higher d13C values (2.6-2.7‰) relative to the other samples. The upper unit of the sections is composed of what was originally calcareous mud. The studied samples have low d13C values (~1.8‰) and notably higher d18O values (~-10.6‰) than the average d18O value of the lower part of the section. The samples from the upper part contain microsparitic cement as an indication of stagnant water environment with calm lacustrine sedimentation and pond facies. Based on our integrated petrographic and microfacies description and stable isotope study, the Budakalász travertine can be classified as an originally thermogene travertine.