摘要
该文研究的轮藻化石采自尼泊尔中西部阿龙科拉地区的比奈科拉组下段。轮藻化石有Nitellopsis (Tectochara)globula(Madler)Grambast et Soulie-Marsche,Chara molassica Straub,C.gigantofusiformis(Yang),Rantzieniella binaiensis sp.nov.,Gyrogona arungensis sp.nov.和Lychnotharnnuspseudoodea(Berger)Soulie-Marsche等,此轮藻化石植物群属新第三纪,可能为中新世晚期。克里雅群轮藻的研究将增添南亚新第三纪地质生态研究的内容。
The Siwalik Group,which is widely distributed and developed in the foredeep of the Himalayas,provides evidence for the rising of the Himalayas. This Group belongs to Miocene-Pleistocene with athickness of several thousand meters. In Nepal,it is called the Churia Group,consisting of the ArungKhola, Binai Khola, Chitwan and Deorali Formations in ascending order. This paper deals with thecharophytes collected from the Lower Member of the Binai Khola Formation in Arung Khola area ofwest--central Nepal. This charophyte flora is Neogene,probably late Miocene in age,including Nitellopsis (Tectochara)globula (Madler) Grambast et Soulie--Marsche, Chara molassica Straub, C. gigantofusiformis (Yang),Rantzieniella binaiensis sp. nov., Gyrogona arungensis sp. nov., Lychnothamnus pseudoodea (Berger),etc. The research on Churia Group charophytes will provide valuable information to the study ofNeogene geoecology of South, Asia. Assemblage characteristics and Age The fossil charophytes described in this paper came from the Lower Member of the Binai KholaFormation belonging to the Churia (Siwalik) Group in the west--central Arung Khola area of Nepal.They were obtained from Samples F12 and F17 from the northern and southwestern parts of thisregion respectively, with relatively poor preservation and low diversity. Charophytes in F12 mostlyhave a short and thick body, with highly calcific spiral cells and rosette(or rasette cover)on the top,such as Nitellopsis (Tectochara) globula(Madler) Grambast et Soulie--Marsche,Rantzieniella binaiensis sp.nov., Gyrogona arungensis sp. nov. Besides, F12 also yields a few forms of Lychnothamnus pseudoodea concave--flat spiral cells, among which Chara molassica Straub is most numerous, and Charagigantofusiformis (Yang) comes next, while Gyrogona arungensis sp. nov. also occurs. Although thefossils from F12 and F17 are different in genera and species, their ages are similar, both belonging toTertiary. For this reason, they are regarded as of one charophyte flora. Of course, F17 appears a littleyounger than F12 based on their fossil features. Nitellopsis (Tectochara) globula and Chara molassica made their first appearances in Late Paleogeneand flourished in Neogene. They can be frequently seen in Middle Oligocene--Late Miocene of southernGermany and Switzerland, and in Late Oligocene--Pliocene of Turkey and China (Madler, 1955;Wang Shui, 1961, 1965; Madler et Staesche, 1979, and others). These two species have beendetermined as members of China's typical Miocene--Pliocene charophyte assemblages from theYoushashan Formation and the Shizigou Formation (Wang Zhen, 1984). Lychnothamnus pseudoodea isthe chief member from the middle and lower Aquitanian of western Switzerland(Berger, 1983), whileChara gigantofusiformis is known from the Upper Member of the Pliocene Qugou Formation in theGonghe Basin,Qinghai,China (Hao Yichun et al.,1983). Rantzieniella so far has only been found inthe Aquitunian of southern France and in the Early Miocene of Lower Luobusha Group in Qusum,Xizang, the Miocene of the Kangcu Formation, and the Pliocene of the Kuca Formation from thewestern Tarim Basin, Xinjiang,China (Grambast, 1962;Wang Zhen 1982; Lu Hui nan et al., 1990);R. binaiensis from Nepal is similar in main characteristics to the known species of the above genus,except for its smaller size and shorter body,while Gyrogona arungensis is an endemic species. To sum up,the charophyte flora from the Lower Member of the Binai Khola Formation,with itsmain part consisting of Nitellopsis (Tectochara) globula, Chara molassica, Rantzienella binaiensis andGyrogona arungensis, belongs to an age which is no earlier than the Agenian (Aquitanian)of Miocene,but no later than the Ruscinian of Early Pliocene; therefore,it is probably Turolian in Late Miocene. The appearance of charophytes in the Binai Khola Formation indicates an environment of slightlyflowing and clean waters with a moderately high pH value. Judging from the spiral cells which havemostly flaked off the gyrogonites,and the broken fossil tops, it is clear that these fossils were
出处
《微体古生物学报》
CSCD
北大核心
1992年第3期311-317,346,共7页
Acta Micropalaeontologica Sinica
关键词
中新世晚期
尼泊尔
轮藻
化石
Charophytes
Late Miocene
Binai Khola Formation
Nepal
