| 浙西皖南晚奥陶世复理石的沉积环境,兼谈鲍马层序应用问题 |
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| 引用本文： | 夏邦栋,吕洪波.浙西皖南晚奥陶世复理石的沉积环境,兼谈鲍马层序应用问题[J].沉积学报,1988,6(4):44-51. |
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| 作者姓名： | 夏邦栋 吕洪波 |
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| 作者单位： | 南京大学地质系 |
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| 摘 要： | 本文研究的复理石具有多种类型的递变层理,有大量波痕,尤其是干涉波痕及浪成波痕发育,古水流方向有双向性,有多级别韵律发育等,说明这一复理石是由波浪、底流、潮流等多种水动力作用叠加而形成的,其沉积环境属浅海直至潮坪。
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| 关 键 词： | 浊流沉积 复理石 复式韵律反递变 双向递变 鲍马层序 |
| 收稿时间： | 1986-07-04 |
A STUDY ON THE ENVIRONMENT OF UPPER ORDOVICIAN FLYSCH IN WESTERN ZHEJIANG AND SOUTHERN ANHUI PROVINCES AND A SHORT COMMENT ON THE APPLICATION OF BOUMA' S SEQUENCE |
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| Institution: | Department of Geology,Nanjing University |
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| Abstract: | The Upper Ordovician flysch deposits with 1200m in thickness occurs in Western Zhejiang Province. The formation was first described by Guan Yinwen etc. in 1959, and it was considered to be shallow marine deposits. Later some reserchers regarded it as a turbidite of deep sea. The authors suggest that this formation is not a turbidite formed in deep sea but a flysch deposited in the area extending from shallow sea to tidal flat. The following characters may be listed; 1.Graded bedding shows diverse types, i.e. graded sand (Aa),graded silt(Ab),and reversal graded silt(Ac). Aa, Ab, and Ac can occur within one of the flysch rhyt-thmic beds. Ab and Ac may be combined to a bidirectional graded bedding Ab-Ac or Ac-Ab. 2.There are a large number of ripple marks, such as current ripple marks,sym-trical and asymmetrical wave built ripple marks and interference ripple marks. The asymmetrical ripple marks and foreset laminations are of bidirectional proprety. 3.There are also sandstones with wave bedding and lenticular bedding. 4.The main direction of sole marks is parallel to the shore line, and there are also bidirectional. 5.Mudstones of the uppermost part of a rhythmic bed contain pelitic or silt gravels,and they often show foreset and lenticular laminations. 6.There are three different grades of rhythmic bed, i.e. gross-rhythmic, fine-rhythmic and micro-rhythmic bedsOne gross-rhythmic bed may contain several fine rhythmic beds,and one fine-rhythmic bed may contain several micro-rhythmic beds which can only be observed by means of microscope. Graded textures, foreset laminations, lenticular beddings, flaser beddings, scour marks, and bioturbations can be found in the micro-rhythmic beds. he facts mentioned above show that the flysch rhythmic beds in the area do ot result from a single kind of process ( such as turbidity currents) in deep sea but from the combination of several processes, such as sea waves, bottom currents, tidal flows, storm surge currents and climatic effects, etc. The most favorable environment in which such diverse kinds of hydrodynamic factors take effect is the area extending from shallow sea to tidal flat. Of course, the sequences of the flysch rhythmic beds, to some extent, are similar to Bouma's Sequence-a sedimentary model about turbidites. It is not very diffic-ult to find out the intervals like A,B,C,D,and E of Bouma's Sequence in the flysch rhythmic beds. According to these characters some reserchers treated the flysch as a deep sea turbidite. It must be pointed out that there are a lot of significant phenomena being ignored by the above-mentioned reserchers. So, we must take a careful and analytic approach in the applications of Bouma's Sequence,and we may not consider the Bouma's Sequence as a conventional and universal model. |
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