摘要
广西百色盆地边缘出露三叠纪地层,盆地中间沉积早第三纪陆相沉积物。田东凹陷位于盆地的东端,在其部分边缘及凹陷的许多钻孔中发现三叠纪地层。在三叠系碳酸盐岩中发现了丰富的有孔虫化石。本文首次正式报道此区三叠纪有孔虫动物群。本文材料是广西石油局勘探研究院提供的,后一作者在工作中制作了大量三叠系石灰岩岩芯和岩屑薄片,经我们对其中所含的有孔虫鉴定后,认识到这些有孔虫动物群大部分属于中三叠世晚期,部分属于中三叠世早期。其后在这些地层中又发现了牙形石、六射珊瑚、海相双壳类,其分布时代与有孔虫是一致的。陈周庆、张富田同志摄影,臧晓泉同志清绘图件,特此致谢。
The middle Triassic strata in the Baise basin so far still remain unstudied since terrestrial deposits of he Palaeogene age cover the whole basin except for the border area where only scattered uotcrops of the Triassic strata have been found. The material which forms the basis of the present study was obtained from the deep wells recently drilled for oil exploration. Although at the present the stratigraphical data are still meager, the rich foraminifera assemblages found from the eleven drilling wells as well as from the outcrops are very helpful for dating the Triassic strata.Two foraminifera assemblages belonging to Anisian and Ladinian respectively were detected in the material. The Anisian foraminifera occurred in the Guohua Formation exposed neat Well B O—16, to the west of Chongshe, in the northwestern Tiandong depression. This formation consists mainly of carbonate deposits of platform and reef facies. The assemblage found in grey to dark grey limestones comprises Endothyra kuepperi, Krikoumbilicus pileiformis, Glomospira sygmaidalis, Trochammina almtalensis, Dentalina hoi, and Triadodiscus sp., although it is not rich in species. Among them, the Anisian element Dentalina hoi of Bulgaria, Poland and west Carpatian indicates a similar age; Trochammina almtalense is also an important element commonly known in the Anisian deposits from Eurasia.The Ladinian assemblage was found from the Hekou Formation which is known only from drilling wells. This formation is mainly composed of carbonate deposits of reef and shallow sea facies; it also contains clastic rocks in some wells. The leading elements of this assemblage are Turriglomina mesotriasica (Koehn-Zaninetti), T. guangxiensis He sp. nov., Palaeolituonella reclinata He sp. nov. Lamelliconus cordevolica (Oberhauser), L. muhispira (Oberhauser) and Aulotortus praegaschei (Koehn-Zaninetti). Among them, Lamelliconus cordevolica (Oberhauser), L. multispina (Oberhauser), Turriglomina mesotriasina (Koehn-Zaninetti) are shared by the assemblage from the Ladinian Yangliujing Formation in Xia'an, Baiceng of Zhenfeng County, Guizhou (He Yah, 1984). Both formations are believed to be deposited in a similar environment within the same sea area.The most comparable foraminifera assemblage so far known outside China is that of the Ladinian reef limestone from South Apennine, Italy (Zaninetti et al., 1987). The common element of both assemblages Turriglomina mesotriasica (Koehn-Zaninetti) is similarly associated with Palaeolituonella, Ophthalmidium and Lamelliconus. The species Turriglomina guangxiensis sp. nov. described in the present paper may be comparable with specimen referred to T. scantonei by Zaninetti et al. (1987, pl. 1,. figs. 1, 3), while Palaeolituonella reclinata sp. nov. is rather close to P. meridionalis from Italy in general morphology.Description of new species Genus Turriglomina Zaninetti, 1987 Turriglomina guangxiensis He sp. nov. (Pl. Ⅱ, figs. 15—18, 21—24, Pl. Ⅳ, figs. 1—4, 9)Test large, elongate; proloculus spherical; tubular second chamber wound irregularly in the early part of the Glomospira-type, and then becoming highly spiralled around an axial column, with 7—9 oblique whorls in the later part and increasing slowly in size during accretion; sutures slightly depressed, oblique in the later part; axial column distinct; wall thick and dense. Length 0.3—0.63 mm; width 0.2mm.This new species is similar in appearance to Turriglomina scandonei Zaninetti, Ciarapica, Martina, Salvini-Bonnard et Rettori, but the latter species differs in having a regular Meandrospiratype early part, nearly plane convolutions and sutures. It is distinguished from Turriglomina mesotriasica by the larger test with a more developed Glomospira-type early part.Occurrence Well Lun-4, Lunyu; Wells Ping-2, Fa-1 and Fa-3, Shangfa, Tiandong county, Middle Triassic Hekou Formation.Genus Palaeolituonella Berezi-Makk, 1981 Palaeolituonella reclinata He sp. nov. (Pl. Ⅰ, figs. 16—19)Test small, elongate, bell-shaped, in early stage slightly curved, with a short trochospiral part, and then becoming uncoiled, rectilinear, with 4 low and wide chambers, increasing in width rapidly; last chamber with an expanded and reversed distal part, without septum-rudiments; aperture simple, terminal and present at each centre of previous chambers; wall thin, consisting of fine granular material. Length 0.37mm; diameter 0.28 mm.The new species is distinguished from Palaeolituonella meridionalis (Luperto) by its smaller and elongate bell-shaped test and thin wall.Occurrence Wells Fa-1 and, Fa-3 Shangfa, Well Lun-4, Lunyu, Tiandong county, Middle Triassic Hekou Formation.
出处
《古生物学报》
CAS
CSCD
北大核心
1991年第2期212-230,291-294,共19页
Acta Palaeontologica Sinica
