湘北九溪、沅古坪下奥陶统等深岩类型、碳氧同位素特征及沉积环境

doi:10.11743/ogg20150505

摘要/Abstract

摘要： 深水环境下等深流沉积研究已经开展50多年，在这50多年里虽然取得了一些成果，但对等深岩的形成机理和沉积环境研究较少。通过野外剖面实测、详细描述和碳氧同位素特征分析，对研究区形成等深岩的环流的特征及不同类型等深岩的形成环境进行了探索。根据其岩性特征，研究区下奥陶统盘家咀组发育有灰泥等深岩、粉屑等深岩、砂屑等深岩、砾屑等深岩和生物屑等深岩5种等深岩相，在垂向上主要发育由单一灰泥等深岩叠置组成的层序、灰泥等深岩与生物屑等深岩组成的层序和灰泥等深岩与砂屑等深岩组成的层序3种不完整等深岩层序和少量的完整等深岩层序。为了研究该等深流沉积形成时的古环境，分别对研究区不同类型等深岩与原地沉积进行系统采样做碳、氧同位素分析。研究表明，工区下奥陶统盘家咀组等深岩的碳同位素δ¹³C值分布于0.18‰～2.31‰，氧同位素δ¹⁸O值的范围为-10.93‰～-9.54‰，盐度指数Z值介于122.91～127.14，温度T值为16.98～24.81 ℃。与原地沉积相比，研究区等深岩的δ¹³C值、Z值、T值均较高，且随着等深岩的粒度增大，其δ¹³C值、Z值、T值均逐渐增高。这表明等深流沉积环境与原地沉积完全不同，等深岩主要形成于高盐度的较深水环境中，且盐度、水温越高，越有助于高能等深流沉积物砂屑等深岩和生物屑等深岩的形成。等深岩层序的形成周期均表现为古盐度、古水温、海平面先增大后减小的周期性变化。

关键词: 碳、氧同位素, 等深岩, 盘家咀组, 下奥陶统, 中扬子台地

Abstract: The literature on deep-water contourites is extensive after more than 50 years of research.However,many unknowns exist in terms of their forming mechanism and sedimentary settings.The article explores the characteristics of circulation and environment for forming various contourites in the Panjiazui Formation of the Lower Ordovician in the study area based on field measured section,detailed description and analyses of carbon and oxygen isotope characteristics.Lithologic analyses show that the formation contains 5 kinds of contourite lithofacies: calearenitie,calcilutite,caleilutitie,gravel and bioclastic contourities.Vertically,three types of incomplete vertical contourite sequences and some complete contourite sequences are recognized.The incomplete sequences include superimposed single calearenitie contourite sequence,interbedding calearenitie contourites and bioclastics contourite sequenceand interbedding calearenitie contourites and caleilutitie contourites sequencece.Systematically sampling and carbon/oxygen isotope analyses of the various contourites and autochthonous deposits indicate δ¹³C values varying between 0.18‰ and 2.31‰,δ¹⁸O values changing from -10.93‰ to -9.54‰,salinity index Z shifting from 122.91 to 127.14,and temperature(T) ranging between 16.98 and 24.81 ℃.Compared with the autochthonous deposits,the contourites in the formation have higher values of δ¹³C,Z and T.With the grain size of the rock getting bigger,these values continue to increase,showing that the sedimentary environment of contourites is totally different from that of the autochthonous deposits.The contourites were mainly formed in relative deep water environment with high salinity,and higher salinity and temperature were more favorable for the formation of certain high-energy contourites,such as caleilutitie and bioclastic contourities.The forming periods of contourite are all characterized by the periodical changes of first increasing and then decreasing palaeo-salinity,palaeo-temperature,and sea level.

Key words: carbon/oxygen isotope, contourite, Panjiaju Formation, Lower Ordovician, Mid-Yangtze platform

中图分类号:

TE121.3

罗顺社,吕奇奇,席明利,等. 湘北九溪、沅古坪下奥陶统等深岩类型、碳氧同位素特征及沉积环境[J]. 石油与天然气地质, 2015, 36(5): 745-755. doi: 10.11743/ogg20150505 Luo Shunshe,Lyu Qiqi,Xi Mingli,et al. Types,carbon/oxygen isotope characteristics and depositional environments of the Lower Ordovician contourites in Jiuxi and Yuanguping of North Hunan Province, China[J]. Oil & Gas Geology, 2015, 36(5): 745-755. doi: 10.11743/ogg20150505

参考文献

[1] 何幼斌,高振中,罗顺社,等.等深流沉积的特征及其鉴别标志[J].江汉石油学院学报,1998,20(4):1-6. He Youbin,Gao Zhenzhong,Luo Shunshe,et al.Features of contourites and their discrimination[J].Jouranal of Jianghan Petroleum Institute,1998,20(4):1-6.
[2] 刘宝珺,余光明,王成善.珠穆朗玛峰地区侏罗系的等深积岩沉积及特征[J].成都地质学院学报,1982,9(1):1-6. Liu Baojun,Yu Guangming,Wang Chengshan.The other deep sedimentary rocks and sedimentary characteristics of Jurassic in the Everest region [J].Jouranal of Chengdu College of Geology,1982,9(1):1-6.
[3] 姜在兴,赵澄林,熊继辉.皖中下志留统的等深积岩及其地质意义[J].科学通报,1989,34(20):1575-1576. Jiang Zaixing,Zhao Chenglin,Xiong Jihui.The Middle-Lower Silurian contourites in Anhui province and their geological significance[J].Chinese Science Bulletin,1989,34(20):1575-1576.
[4] 虞子冶,施央申,郭令智.广西钦州盆地志留纪—中泥盆世等深流沉积及其大地构造意义[J].沉积学报,1989,7(3):21-29. Yu Ziye,Shi Yangshen,Guo Lingzhi.The paleocontourite and its tectonic significance in Qinzhou Basin,Guangxi,China[J].Acta Sedi-mentologica Sinica,1989,7(3):21-29.
[5] 段太忠,郭建华,高振中,等.华南古大陆边缘湘北九溪下奥陶统碳酸盐等深岩丘[J].地质学报,1990,64(2):131-143. Duan Taizhong,Guo Jianhua,Gao Zhenzhong,et al.A Lower Ordovician carbonate contourite drift on the margin of the south China palaeocontinent in Jiuxi,northern Hunan[J].Acta Geologica Sinica,1990,64(2):131-143.
[6] 刘宝珺,许效松,梁仁枝.湘西黔东寒武纪等深流沉积[J].矿物岩石,1990,10(4):43-47. Liu Baojun,Xu Xiaosong,Liang Renzhi.Contourites of Cambrian in western Hunan and eastern Guizhou[J].Mineralogy and Petrology,1990,10(4):43-47.
[7] 高振中,罗顺社,何幼斌,等.鄂尔多斯地区西缘中奥陶世等深流沉积[J].沉积学报,1995,13(4):16-25. Gao Zhenzhong,Luo Shunshe,He Youbin,et al.The Middle Ordovician contourite on the west margin of Ordos[J].Acta Sedimentologica Sinica,1995,13(4):16-25.
[8] Bein A,Weiler Y.The Cretaceous Talme Yafe Formation:a contour current shaped sedimentary prism of calcareous detritus at the continental margin of the Arabian Craton[J].Sedimentology,1976,23(4):511-532.
[9] 葛祥英,牟传龙,周恳恳,等.湖南奥陶纪沉积演化特征[J].中国地质,2013,40(6):1829-1841. Ge Xiangying,Mou Chuanlong,Zhou Kenken,et al.Characteristics of Ordovician sedimentary evolution in Hunan province[J].Geology in China,2013,40(6):1829-1841.
[10] Kaufman A J,Jacobsen S B,Knoll A H.The vendian record of Sr and C-isotopic variations in seawater:Implications for tectonic and paleoclimate[J].Earth and Planetary Science Letters,1993,120(3-4):409-430.
[11] Kaufman A J,Knoll A H.Neoproterozoic variations in the C-isotopic composition of seawater:Stratigraphic and biogeochemical implications[J].Precambrian Research,1995,73(1-4):27-49.
[12] 严兆彬,郭福生,潘家永,等.碳酸盐岩C,O,Sr同位素组成在古气候、古海洋环境研究中的应用[J].地质找矿论丛,2005,20(1):53-56. Yan Zhaobin,Guo Fusheng,Pan Jiayong,et al.Applicatin of C,O and Sr isotope composition of carbonates in the research of paleocliate and paleooceanic environment[J].Geology and Mineral Resources Research,2005,20(1):53-56.
[13] 陈强,张慧元,李文厚,等.鄂尔多斯奥陶系碳酸盐岩碳氧同位素特征及其意义[J].古地理学报,2012,14(1):117-124. Chen Qiang,Zhang Huiyuan,Li Wenhou,et al.Characteristics of carbon and oxygen isotopes of the Ordovician carbonate rocks in Ordos and their implication[J].Journal of Palaeogeography,2012,14(1):117-124.
[14] 罗顺社,汪凯明.河北宽城地区中元古代高于庄组碳酸盐岩碳氧同位素特征[J].地质学报,2010,84(4):492-499. Luo Shunshe,Wang Kaiming.Carbon and oxygen isotope composition of carbonate rock from the Mesoproterozoic Gaoyuzhuang Formation in the Kuancheng area,Hebei province [J].Acta Geologica Sinica,2010,84(4):492-499.
[15] 刘德良,孙先如,李振生,等.鄂尔多斯盆地奥陶系白云岩碳氧同位素分析[J].石油实验地质,2006,28(2):155-160. Liu Deliang,Sun Xianru,Li Zhensheng,et al.Analysis of carbon and oxygen isotope on the Ordovician dolostones in the Ordos basin [J].Petroleum Geology & Experiment,2006,28(2):155-160.
[16] 张秀莲.碳酸盐岩中氧、碳稳定同位素与古盐度、古水温的关系[J].沉积学报,1985,3(4):17-29. Zhang Xiulian.Relatinship between carbon and oxygen stable isotope in carbonate rocks and paleosalinity and paleotemperature of seawater[J].Acta Sedimentologica Sinica,1985,3(4):17-29.
[17] 罗顺社,张建坤,汪凯明,等.燕山地区中元古界碳酸盐岩碳、氧同位素特征及其环境意义[J].石油天然气学报,2009,31(6):18-24. Luo Shunshe,Zhang Jiankun,Wang Kaiming,et al.The Mesoprotero-zoic carbonate carbon and oxygen isotopic characteristics and its environmental significance in Yanshan area [J].Journal of Oil and Gas Technology,2009,31(6):18-24.
[18] 旷红伟,李家华,罗顺社,等.燕山地区1.6～1.0 Ga时期碳酸盐岩碳、氧同位素组成、演化及其地质意义[J].地学前缘,2009,16(5):118-133. Kuang Hongwei,Li Jiahua,Luo Shunshe,et al.The C and O isotopic compositions and their evolution recorded in the carbonate interval of the Yanshan area from 1.6 to 1.0 Ga,and their geological implications[J].Earth Science Frontiers,2009,16(5):118-133.
[19] Korte C,Kozur H W,Veizer J.δ¹³C and δ¹⁸O values of Triassic brachiopods and carbonate rocks as proxies for coeval seawater and palaeotemperature[J].Palaeogeography,2005,226(2):287-306.
[20] Keith M H,Weber J N.Isotopic composition and environmental classification of selected limestone and fossils[J].Geochem Cosmochim Acta,1964,28(10):1787-1816.
[21] Mackenzie F T.Sedimentary cycling and the evolution of sea water[C]／／ Riley J P.Chemieal oceanography (2nd ed).London:Academic Press,1975:309-364.
[22] 邵龙义.碳酸盐岩氧、碳同位素与古温度等的关系[J].中国矿业大学学报,1994,23(1):39-45. Shao Longyi.The relation of the oxygen and carbon isotope in the carbonate rocks to the paleotemperature etc[J].Journal of China University of Mining & Tecchnology,1994,23(1):39-45.
[23] Craig H.Standard for reporting concentrations of deuterium and oxygen-18 in natural water[J].Science,1961,133(23):1833-1834.