【摘要】 本文对甘肃玉门花海地区中更新世内陆盐湖相沉积物中保存完好的广盐性介形类 Eucypris mareotia ( Fischer , 1855 )和广盐性有孔虫 Ammonia beccarii ( Linné , 1758 ),以及极少量保存很差的钙质超微化石为代表的微体化石群特征进行了简述;对化石群中各门类化石的保存和埋葬状况进行了分析;探讨了有孔虫和钙质超微化石的来源;对非海相沉积物中有孔虫的变异进行了分析和研究。研究结果进一步证实,广盐性有孔虫在远离海洋的内陆盐湖环境中,在适宜的盐度条件下,有生存和繁殖的可能性。更多还原

【Abstract】 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.更多还原