Dombayova Grabeni (Dinar, Batı Anadolu) Pliyosen Çökellerinin Palinolojik Verilere Dayalı Paleovejetasyonel Ve Paleoiklimsel İncelenmesi

Abstract

Paleoclimatic and paleoenvironmental reconstructions based on palynofloras and ostracod faunas are made from Pliocene coal bearing sedimentary sequences of Dombayova Graben-Afyonkarahisar within this study. Two different localities are sampled in the graben. These are: Early Pliocene (MN 14) Akçaköy section located at the eastern margin of the graben and Pliocene core D-97 located at the center of the graben. Akçaköy section is represented by five meters thick sedimentary succession deposited in lacustrine and fluvial environments. The analysis reveal 82 palynomorphs including 29 species, 47 genus. The palynological assemblage contains angiosperms (76,8%), gymnosperms (12,1%), pteridophytes (2,43%) and fresh-water algae (8,67%). Arboreal taxa defined from Akçaköy coals is predominantly characterized by mixed mesophytic forest (deciduous Quercus, Cedrus, Cathaya, Tsuga, Picea, Podocarpidites) and rare riparian forest elements (Taxodium/Glyptostrobus, Alnus, Salix, Carya, Ulmus) accompanied by dominant herbaceous taxa (Poaceae, Chenopodiaceae/Amaranthaceae, Asteraceae-Tubuliflorae type). Results of pollen analysis also reveal the important role of aquatic taxa (Sparganium, Cyperaceae:Carex/Cladium). In addition, the section involves relatively high abundance of non-pollen palynomorphs (NPP) such as Stigmozygodites, Tetraporina, Spirogyra, Botryococcus braunii, Sigmopollis laevigatoides, Sigmopollis sp., Sigmopollis punctatus. Semi-quantitative analysis indicates presence of warm temperate climatic conditions during deposition of Akçaköy section. The D-97 core, located at the center of the graben, is 320 meters long, and it has a 90 meter thick coal and siltstone-mudstone alternations. According to the palynological analysis 19 families, 61 genus and 12 species are identified. The identified elements consist of: 64% angiosperm (21% arboreal, 43% non-arboreal), 11% gymnosperm, 6% pteridophyta and 19% NPP. The fossil palynoflora of core D-97 are predominated by herbs and shrubs. Cyperaceae, Poaceae, Asteraceae, Chenopodiaceae/Amaranthaceae are the most dominant elements. NAP/AP (non-arboreal/arboreal plants) ratio is very high compared to Akçaköy section indicating the availability of more open landscapes, which may have been the result of cooler and more continental conditions of that time interval. The arboreal taxa of D-97 core, despite its low abundance, has notable vegetational dynamic. High-altitude elements (Abies, Picea) and Cupressaceae appear only at the early phase of the section. Mid-altitude elements (Cedrus, Sciadopitys, Tsuga, Cathaya) and mesothermic elements (Carpinus orientalis, Ostrya, Juglans, Acer, deciduous Quercus, Populus, Alnus, Salix, Carya, Pterocarya, Ulmus) appear rhythmically throughout the section. This cyclicity may indicate the presence of humid phases within the sequence. Fluctuations in the abundance of palynomorphs also reveal that environment has been tectonically and climatically disturbed at the time of deposition. Results show that the vegetation dynamics passed through several phases, in conjuction with changes in paleoclimate and paleoecological conditions. D-97 core also includes high abundance of NPPs. These are: Sigmopollis laevigatoides, Ovoidites minoris, Tetraporina, Ovoidites elongatus, Ovodites gracilis. The abundance of NPPs in D-97 core is higher than that of Akçaköy samples indicating a shallow and oxygen rich water body. 18 Ostracoda samples are taken from the appropriate levels of D-97 core. Ostracoda analysis revealed presence of 7 genus ans 8 species. These forms are: Zonocypris membranae, Heterocypris sp., Prionocypris zenkeri, Candona angulata, Candona neglecta, Ilyocypris bradyi, Darwinula stevensoni ve Amplocypris sp. Based on the identified forms, it is possible to say that during the time of deposition a shallow and relatively cold aquatic environment existed.