新疆准噶尔盆地北缘新近系顶山盐池组及相关地层问题

在新疆准噶尔盆地北缘乌伦古河流域建立了一个新近纪岩石地层单位:顶山盐池组。该组平行不整合于哈拉玛盖组之上,是一套以红色泥质粉砂岩为主体的细碎屑岩堆积,厚约50 m,含有上下两个化石带。上化石带时代为中新世晚期或上新世;下化石带为中中新世中晚期,与通古尔期默尔根小哺乳动物群大体相当。根据岩性和化石组合,推测顶山盐池组含有风成沉积物,或主要为风成堆积。其下部地层与流域中可可买登组为同期异相沉积。通过下伏的哈拉玛盖组,顶山盐池组可以和附近地区的铁尔斯哈巴合剖面衔接,构成乌伦古河流域一个从晚渐新世到中新世晚期或上新世大体连续的地层序列。这个序列有可能包含了塔本布鲁克期至保德期的沉积物和动物群。我们将这个序列与中国以及欧洲的相同时段生物年代序列进行了初步的对比,并讨论了有关的生物年代和年代地层问题。以哈拉玛盖动物群为代表的中中新世动物群的繁盛与它们的地理分布和中中新世全球气候最佳期的温暖气候可能相关。

THE NEOGENE DINGSHANYANCHI FORMATION IN NORTHERN JUNGGAR BASIN OF XINJIANG AND ITS STRATIGRAPHIC IMPLICATIONS

A new lithological unit,the Dingshanyanchi(Dingshan Salt Lake)Formation,is estab- lished based on a set of reddish silts that is distributed in the area of Dingshan Salt Lake in the southern area of the Ulungur River,northern Junggar Basin,Xinjiang(Fig.1).At the type lo- cality,the Dingshanyanchi Formation measures 46.2 m in thickness,overlays the Middle Mio- cene Halamagai Formation,and is capped by a set of 5 m thick conglomerates of unknown age (Fig.2).Along the escarpment,the contact between the Halamagai and Dingshanyanchi for- mations varies from place to place.In some areas,a hiatus is distinct between the two units, whereas in others they appear continuous.We tentatively consider that a disconformity exists between the two formations and that the hiatus,if any,does not represent a major sedimentary gap.