B. Papp szerk.: Studia Botanica Hungarica 30-31. 1999-2000 (Budapest, 2000)

Erdei, Boglárka; Lesiak, Maria: A study of dispersed cuticles, fossil seeds and cones from Sarmatian (Upper Miocene) deposits of Sopron-Piusz puszta (W Hungary)

Geological setting The geological setting is discussed on the basis of ROSTA (1993) and FODOR et al. (1989). The oldest formations of the region are Palaeozoic crystalline rocks forming the basement of the basin (Fig. 2). The overlying rocks above a great unconformity are of Neogene since Mesozoic and Palaeogene sequences are missing. The deposition of Neogene sediments started in the Early Miocene. At the beginning of the Badenian subsidence of the region had begun but its was lower than that of sedimentation (Badenian Clay, Lajta Limestone), thus, filling up of the region took place. The Kőhidafault zone was formed, as early as the end of the Badenian. The subsidence started again during the Sarmatian and resulted in a sedimentation similar to that of the Badenian. It was during the middle part of the Sarmatian when uplift of the frame of the Sopron-Kismarton basin started. Sand and gravel characterised the Upper Sarmatian deposits and finally the stage ended with a regression. During the Early Pannonian due to the repeated subsidence of the basin lacustrine sediments of great thickness were deposited. In the middle part of the Pannonian the area became subaerially exposed and Pleistocene sedimentation was characterised by sandy and clayey loess and gravel. ROSTA (1993) recognised a Gilbert-type delta in the Miocene of the region (Fig. 3). In the 30 m thick sequence she has identified 7 facies based on penological, sedimentological and palaeontological characteristics (Fig. 4). The sequence represents two cycles of a Gilbert-type delta having the second one incomplete. The "A" facies of the prodelta is constructed of mainly unsorted sandy gravel interfingered by laminated coaly clay streaks of 1-10 cm thickness. These layers consist the plant debris being likely to have originated from the delta plain represented by "D" and "E" facies. "B" and "C" facies are identified as the deltafront. "F" facies is a new deltafront covered discordantly with open water sediments ("G" facies). According to molluscs, ostracods and foraminifers the "A"-"E" facies are of Sarmatian (Late Sarmatian) age. In facies "F" the appearance of Lower Pannonian ostracods is recorded. Fig. 1. Geographical position of the site.