Microfossils in Non-Marine Quaternary Sediments from Yumen of Gansu Province, China
详细信息
- 责任者：Gou Yunxian (Nanjing Institute of Geology and Palaeontology ; Chinese Academy of Sciences ; Nanjing 210008 ; China) ; Zhang Binggao
- 刊名：Acta Micropalaeontologica Sinica
- 出版年：2013
- 卷期：30(1)
- 页码：p.49-57
- issnNo：ISSN1000-0674
- isbnNo：CN32-1189/Q
摘要
Fifteen nonmarine Quaternary samples are analyzed from the Middle Pleistocene saline-lacustrine deposits of Yumen, Gansu Province. A plentiful valves of Eucypris mareotica (Fisher, 1855) (Ostracoda) associated with a small number of Ammonia beccarii (Linné, 1758) (Foraminifera) are encountered in some of these samples, however sometimes E. mareotica presents alone in another samples. Besides, a few nannofossils are also found in some samples. E. mareotica is a typical salt lake ostracod species, appearing from the Pleistocene to Recent, and it is exactly an euryhaline one. Its saline tolerance ranges from 5‰ to >100‰. A. beccarii, emerging from the Miocene to Recent, is a shallow-water benthic form. It is also an euryhaline species, with the salinity from 0‰ to >90‰. A. beccarii is widely spread in the sea and marine-continental trasitional areas, while it is also found in recent salt lakes and Quternary saline-lacustrine sediments in inland basins in China, which are located far from the sea. Both E. mareotica and A. beccarii comprise adults and a large number of juveniles. They are well preserved almost without broken and dissolved specimens. The variation, distinguished from the normal marine forms of A. beccarii, shows in the juveniles. Based on the state of the preservation, the population composition and the special variation in juveniles of A. beccarii, it is suggested that both E. mareotica and A. beccarii should be Middle Pleistocene autochthonous biocoenoses of monospecific fossil faunas in the studied area. Sohn and Kornicker (1979) proposed that some ostracods may have been widely distributed because of the circumglobal transport of eggs by high altitude winds at low temperature and pressure. Afterwards according to the discovery of the euryhaline foraminifera from late Quaternary salt lake deposits in Chaidamu Basin, Sun Zhencheng et al. (1992) suggested that air pathway is a possible route for organism transmission with neither the sea transgression nor a remnant sea. The authors of present paper support the views stated above. It means that A. beccarii may have been imported by high allitute winds or other ways and lived in studied area. Nannofossils are represented by a few specimens of Watznaueria barnesae, Biantholithus sparsus, Coccolithus pelagicus etc., which belong to different geological preriods. In addition to their poor preservation, and rare occurrence, it is inferred that the nonnofossils are exotically transported elements to the Middle Pleistocene sediments in studied area.