Micromorphology and mineralogy of the Eocene calcrete gravel from the Mecsek Mountains (S Hungary)

Abstract

Redeposited Eocene calcrete gravel was found in a Miocene conglomerate sequence in the Western Mecsek Mountains, S Hungary. The purpose of this paper is to describe the micromorphological and mineralogical characteristics of these rocks. A large number of calcrete thin sections were analyzed using a petrographic microscope. This study was supplemented by microchemical staining, cathode luminescence examination and X-ray diffraction methods.  The diagnostic features identified are rhizoliths (rhizocretion, root cast and root petrifaction), alveolar textures, in situ Microcodium grains, peloids, coated grains and pedogenic voids. According to these micromorphological results the studied calcrete belongs to the group of beta calcretes. The biofabric of this calcrete reflects an extensive vegetation cover and a relatively high degree of biological activity. Micromorphology and mineralogical composition of the calcrete gravels (i.e. dominance of calcite, quartz, illite±muscovite and illite/smectite) suggest a ...