| 鄂西二叠系生物礁的基本特征及其发育规律 |
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| 引用本文： | 范嘉松,张维,马行,张荫本,刘怀波.鄂西二叠系生物礁的基本特征及其发育规律[J].地质科学,1982,0(3):274-282. |
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| 作者姓名： | 范嘉松 张维 马行 张荫本 刘怀波 |
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| 作者单位： | 1. 中国科学院地质研究所;2. 四川石油局地质勘探开发研究院;3. 江汉石油学院 |
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| 摘 要： | 鄂西二叠系生物礁分布于利川县境,它是由海绵、水螅等造架生物组成的典型的生物礁,其层位属晚二叠世长兴组,出露于见天坝、黄泥塘等地(图1)。此生物礁从出露之完整、化石之丰富、结构之清楚来看,是我国最发育的生物礁之一。
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| 关 键 词： | , |
| 收稿时间： | 1981-03-23 |
| 修稿时间： | 1981-03-23; |
THE UPPER PERMIAN REEFS IN LICHUAN DISTRICT, WEST HUBEI |
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| Fan Jiasong,Zhang Wei,Ma Xing,Zhang Yinben,Liu Huaibo.THE UPPER PERMIAN REEFS IN LICHUAN DISTRICT, WEST HUBEI[J].Chinese Journal of Geology,1982,0(3):274-282. |
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| Authors: | Fan Jiasong Zhang Wei Ma Xing Zhang Yinben Liu Huaibo |
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| Institution: | 1. Institute of Geology, Academia Sinica, Beijing;2. Institute of Geological Exploration and Development, Sichuan Petroleum Administration;3. Jianghan Petroleum College |
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| Abstract: | 1.Introduction The Upper Permian reefs are widely distributed in Lichuan district,West Hubei,where they are the typical reefs built up by caleisponges and hydrozoan as their frame-building organisms.Their stratigraphical horizon corresponds to Upper Permian Chang-xing Formation.The outcrops of the reefs well expose in Jiantianba,Huangnitang and other localities,Lichuan County.The complete exposure of the reef sequence,the abundance of framebuilding organisms and the distinctness of reef textures and structures make,the Upper Permian reefs in West Hubei become one of the best developed reefs in South China.2.The main features of Jiantianba reef in Lichuan district and its facies or stages of its development or growth.(a)Basin faciesBefore the growth of Upper Permian reefs,the basement for developing the reefs was mainly composed of dark grey and black grey thintomedium bedded spiculitic-calcispherical micrites intercalated with cherty bands and spiculitic siliceous rocks,which represents the typical deposits in deep-water basin.In the basal part,some well-preserved radiolarias have been found.(b)Pore-reef and slope facies or the initial stage of reef growth.Upwards the sediments superimposed represent the initial stage of Upper Permian reef growth,which consists of whitish grey,brown grey thick-bedded and massive sponge-skeletal limestones with the first appearance of f ramebuilding organisms-Sphinctozoa and binding organisms such as blue-green algae and Tubiphytes.In the sponge skeletal limestone some beds of fore-reef slump breccia can be distinguished as thin-bedded layers with wedges intertongued into reef limestone.(c)Reef-core facies Overlying the deposits mentioned above are the sediments of reef-core facies,which represent the most developed stage of reef growth.The reef-core is composed of grey to dark-grey,non-bedded reef-limestones.Organisms found in the reef can be classified into three groups:1) frame builders; 2) binders; 3) accessory organisms.The frame-building organisms are well-preserved Sphinctozoa,Inozoa,Hydrozoan and stromatoporoids.The binding organisms are blue-green algae and Tubiphytes.The accessory organisms including echinoderms,.brachio-pods,gastropods,foraminifers and bryozoan are very rich and often appear as fragments,Here Tubiphytes play an important role in encrusting and binding reef in addition to laminar blue-green algae being in the habit of prominent encrusting.In the reef core,the frame-building organisms or laminar blue-green algae are often surrounded by fibrous calcites,which represent the early cementation of filling the pores within the reefs.In the low burial stage,hypersaline water from lagoonal area seeped into permeable reef area to prompt early forming dolomites outside the fibrous calcite layers.The remaining cavities in the reef were later filled by sparry calcites.It indicates that the interstitial lime mud materials often constitute a greater portion of the reef-debris.These lime muds might be the products of breakage of various organisms,or the products of the bioactivity related to blue-green algae.The frame-building Sphinctozoa and Inozoa are listed as follow:Amblysiphonella,Girtycoelia,Waagenella,Colospongia,Sollasia,Cystauletes,Peronidella,Rhabdactinia.Four new genus,including Lichuanospongia,Polycystocoelia,Sinocoelia,Stromatocoelia,have been established.The Hydrozoan include the following genus:Palaeoaplysina,Spongiomorpha and others.In the top of the reef-core,the sediments were dolomitized by the interaction of saline water with the fresh water on the superficial exposures of reef and the strong leaching by fresh water.The major deposits are composed of white grey massive medium-crystalline dolomites with remaining echinodermal fragments and other bioclasts.(d)Back-reef faciesThe lagoonal deposits representing the back reef facies are an intercalation of dark grey medium-to-thick bedded echinodermal algal bioclastic limestones with medium-to-thick bedded dolomites and ealcidolomites.The sequences of Permian reef are overlain by the back-reef lagoonal deposits gradually encroached on the reef during the process of progradation of carbonate platform towards the open sea, thus the history of the reef growth eventually ended.Based on the general characteristics of the reef growth development in West Hubei,the reefs exposed in Huangnitang are very similar to those at Jiantianba locality in the same region, but differ from the latter in larger amount of lime mud and less evident encrustine texture formed by fibrous calcites. |
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