Pollen and Spores from the Lower Cretaceous of Central Mongolia and Their Paleoclimatic Significance ()
1. Introduction
Coal-bearing strata from Central Mongolia (Khukhteeg Formation) of Aptian to Albian age contain next to dominating Pinaceae, Cupressaceae pollen [1] - [5] . The Khovil opencast mine is located in Central Mongolia southeast of Ulaanbaatar in the Choir-Nyalga Basin. The Choir-Nyalga Basin is the result of extensional tectonics that was prevalent during the Lower Cretaceous north-south trending fold and thrust belt in the central of Mongolia [6] [7] . The sediments of the Khovil opencast mine belong to the lithostratigraphic unit of the coal-bearing Khukhteeg Formation which is, part of the Zuunbayan Group. The Khukhteeg Formation includes conglomerates, gravels, sandstones, and thick lignite coal [7] .
2. Material and Methods
A total of 25 samples collected from Khovil opencast mine. The samples were treated with HCl and HF using standard palynological procedures then fossil pollen grains were investigated by scanning electron microscope (SEM). In Figure 1, SEM photos are presented.
3. Results and Conclusion
Palynological assemblage is characterized by the abundant of fern spores Cyathaceae and Schizaeaceae, Selaginellaceae, Lycopodiaceae and pollen Pinaceae, Podocarpaceae (Figure 1). In this assemblage, not observed spores Appendicisporites, very rare pollen Cedripites, contain chlorantahaceous angiosperms Clavatipollenites and unknown angiosperm pollen Retimonocolpites, Liliacidites-like, Platanus-like.
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Figure 1. Spores and pollen from Khukhteeg Formation: (1)Taurocusporites reduncus, 5453×, 2 µm (2) Taxodiaceaepollenites sp., 8830×, 10 µm (3) Lycopodiumsporites marginatus, 6829×, 10 µm (4) Cicatricosisporites dorogensis, 5907×, 20 µm (5) Aequitriradites spinulosus, 4293×, 30 µm (6) Schizosporis sp., 5907×, 50 µm (7) Pilosisporites notensis, 5907×, 30 µm (8) Pilosisporites sp., 5907×, 30 µm (10) Lycopodium sp., 6829×, 10 µm (10) Podocarpites luteus 3566×, 10 µm (11) Podocarpites multisinus 3701×, 10 µm (12) Piceapollenites sp., 2313×, 50 µm.
This palynological assemblage is important for inferring paleoecological and paleoclimatic conditions of the region during the Early Cretaceous. The assemblage is dominated by pollen of conifers, such as Pinaceae, Taxodiaceae, indicating the vegetation of conifer forests. The assemblage contains abundant above mentioned pollen taxa, which are generally associated with wet habitats. The conifer plants grew on foothills at different distances from the lake, but Filicopsida dominated the lake shore. Clavatipollenites is also khown from lower latitudinal fossil localities (Spain, Portugal, Brazil, USA) and their presence in Mongolia might be evidence for the admixture of temperate and subtropical floras [8] . The Choir-Nyalga basin, which was a periodically ever-wet (presence of algal cysts, Botryococcus and liverworts Aequitriradites), low diverse peat producing environment situated in a more northern position at higher latitudes, where newcomers arrived later than at the lower latitudes.
Acknowledgements
We want to express our deep gratitude to Christa-Ch Hofmann (University of Vienna), Freddy Grimsson (University of Vienna) for improving the manuscript. Special thanks go to Altanzul Chikalov, Munkhnasan Otgon for outstanding fieldwork. This research has been supported by Ernst Mach Grant from the Austrian Federal Ministry of Education, Science and Research (BMBWF). This is a contribution to UNESCO/IUGS/IGCP 679 project.