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

Raucsikné Varga, Andrea Beáta and Szakmány, György and Raucsik, Béla (2002) Micromorphology and mineralogy of the Eocene calcrete gravel from the Mecsek Mountains (S Hungary). ACTA GEOLOGICA HUNGARICA, 45 (3). pp. 287-299. ISSN 0236-5278

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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 semi-arid/subhumid climate during calcrete pedogenesis. Within the Eocene calcrete gravel two main cement types have been distinguished: a meteoric vadose cement (vadose silt) and a phreatic one (drusy ferroan calcite spar). Drusy sparite is the typical cement of near-surface diagenesis, and this, together with its ferroan nature, leads to the conclusion that the main site of cementation of the Eocene calcrete was the meteoric phreatic zone.

Item Type: Article
Subjects: Q Science / természettudomány > QD Chemistry / kémia > QD06 Mineralogy / ásványtan
Q Science / természettudomány > QE Geology / földtudományok
Depositing User: MTMT SWORD
Date Deposited: 13 Nov 2013 07:44
Last Modified: 13 Nov 2013 07:44

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