Reconstruction of atmospheric CO2 from ice-core data and the deep-sea record of ontong Java plateau: the Milankovitch chron     

Wolfgang H. Berger  Memorie K. Yasuda  Torsten Bickert  Gerold Wefer 《International Journal of Earth Sciences》1996,85(3):466-495

We provide a reconstruction of atmospheric CO₂ from deep-sea sediments, for the past 625000 years (Milankovitch chron). Our database consists of a Milankovitch template of sea-level variation in combination with a unique data set for the deep-sea record for Ontong Java plateau in the western equatorial Pacific. We redate the Vostok ice-core data of Barnola et al. (1987). To make the reconstructions we employ multiple regression between deep-sea data, on one hand, and ice-core CO₂ data in Antarctica, on the other. The patterns of correlation suggest that the main factors controlling atmospheric CO₂ can be described as a combination of sea-level state and sea-level change. For best results squared values of state and change are used. The square-of-sea-level rule agrees with the concept that shelf processes are important modulators of atmospheric CO₂ (e.g., budgets of shelf organic carbon and shelf carbonate, nitrate reduction). The square-of-change rule implies that, on short timescales, any major disturbance of the system results in a temporary rise in atmospheric CO₂.  相似文献   

The Silurian of Gotland (Sweden): facies interpretation based on stable isotopes in brachiopod shells     

Chr Samtleben  A. Munnecke  T. Bickert  J. Pätzold 《International Journal of Earth Sciences》1996,85(2):278-292

The Silurian of Gotland, Sweden, consists of 440 m of carbonate deposits. Repeatedly, uniform sequences of micritic limestones and marls are interrupted by complex-structured reefs and by adjacent platform sediments. Generally, the alteration of facies is interpreted as the result of sea-level fluctuations caused by a gradual regression with superimposed minor transgressive pulses. The purpose of this study is a facies interpretation based on both field observations and stable isotope measurements of brachiopod shells. Approximately 700 samples from stratigraphically arranged localities in different facies areas have been investigated. The carbon and oxygen isotopes show principally parallel curves and a close relationship to the stratigraphic sequence. Lower values occur in periods dominated by deposition of marly sequences. Higher values are observed in periods dominated by reefs and extended carbonate platforms. The oxygen isotope ratios are interpreted to reflect paleosalinity changes due to varying freshwater input, rather than to paleotemperature. Carbon isotope ratios are believed to have been connected to global changes in the burial of organic carbon in black shales during periods of euxinic deep water conditions. Consequently, the facies succession on Gotland results from global paleoclimatic conditions. Changes in terrigenous input due to different rates of weathering and freshwater runoff, rather than sea-level fluctuations, control the carbonate formation of the Silurian on Gotland.  相似文献   

碳酸盐岩地区电磁波场的特性分析     

刘海滨  佟文琪 《世界地质》1996,15(1):82-87

形成岩溶的高阻碳酸盐岩对电磁波的吸收较弱，而且成层沉积的特定环境使碳酸盐岩地区岩石的各向异性现象较明显，由于地空界面的存在及岩溶洞壁两侧介质电性差异明显，界面清晰，又使电磁波出现强烈的反射及散射现象，从理论上对碳酸盐岩地区电磁波传播的特有现象进行了研究和分析，并给出结论。  相似文献   

碳酸盐岩的反射光谱特征的研究及应用   总被引：2，自引：0，他引：2  

傅碧宏 《岩矿测试》1996,15(3):207-209

在室内对新疆塔里木盆地西北缘柯坪地区碳酸盐岩的反射光谱进行了测量。分析结果表明：碳酸盐岩的特征吸收谱带位于２３００～２３５０ｎｍ，随着碳酸盐岩中Ｍｇ２＋含量的增加，其特征吸收谱带的中心波长位置具有向短波长方向移动的特点；同时，随着碳酸盐岩中碳酸盐矿物含量的增加，其特征吸收谱带的深度（Ｄ）也有增大的趋势，并且岩石的平均反射率（Ｒ）也随着增高。根据这些特征可以判定碳酸盐岩的岩石类型及碳酸盐矿物的相对含量  相似文献   

Erosion rates of alpine bedrock summit surfaces deduced from in situ Be and Al     

Eric E. Small  Robert S. Anderson  James L. Repka  Robert Finkel 《Earth and Planetary Science Letters》1997,150(3-4):413-425

We have measured the concentration of in situ produced cosmogenic ¹⁰Be and ²⁶Al from bare bedrock surfaces on summit flats in four western U.S. mountain ranges. The maximum mean bare-bedrock erosion rate from these alpine environments is 7.6 ± 3.9 m My⁻¹. Individual measurements vary between 2 and 19 m My⁻¹. These erosion rates are similar to previous cosmogenic radionuclide (CRN) erosion rates measured in other environments, except for those from extremely arid regions. This indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments, even though frost weathering should be intense in these areas. Our CRN-deduced point measurements of bedrock erosion are slower than typical basin-averaged denudation rates ( 50 m My⁻¹). If our measured CRN erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion, then relief in the mountain ranges examined here is probably increasing.

We develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady-state erosion model to episodically eroding outcrops. Our simulations show that interpreting measurements with the steady-state erosion model can yield erosion rates which are either greater or less than the actual long-term mean erosion rate. While errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples, the mean value of many steady-state erosion rate measurements provides a much better estimate of the long-term erosion rate.  相似文献   

The hydrocarbon generation mechanism and the three-stage type model of hydrocarbon generation for carbonate source rocks   总被引：1，自引：0，他引：1  

Zhaoyun Wang  Keming Cheng 《中国科学D辑(英文版)》1997,40(3):232-238

The diagenetic mechanism and process of carbonate rocks, which is different to that of clastic rocks, decides the existence of different existing state organic matters in carbonate rocks. This has been verified by both the microscopic observation of organic petrology and the analysis of organic geochemistry of many samples. Based on the hydrous pyrolysis simulation experiment of the low-mature carbonate rocks, the contrasting study on the yield and their geochemistry characteristics of different existing state soluble organic matters of a series of various maturity samples shows that the different existing state organic matters make different contributions to hydrocarbon generation during every evolution state. So that, the hydrocarbon generation process of carbonate rocks can be summarized as the following three stages: the first is the direct degradation of biogenic bitumen macromolecules during the immature stage, the second is the thermal degradation of a large amount of kerogen at the mature stage, the last stage is the expulsion or release of inclusion organic matter owing to the increased thermal expansion pressure during the high evolution stage. Part of achievements of the Eighth Five-Year National Science-Technology Key-Task Project “85-102-02-07”.  相似文献   

大港油田奥陶系碳酸盐岩生物标志化合物地球化学特征   总被引：5，自引：1，他引：5  

刘洛夫  王春江 《沉积学报》1997,15(3):78-83

在本项研究中，根据Ｐｒ／Ｐｈ比值，β－胡萝卜烷类化合物丰度，甾／藿比值，单甲基高位取代支链烷烃，ＯＥＰ值，升藿烷Ｃ３１２２Ｓ／（２２Ｓ＋２２Ｓ）比值等参数，对大港油田奥陶系碳酸盐岩的地球化学特征作了详细的研究，该为该套地层只于弱氧化－弱还原条件下及经历了强烈的细菌改造。  相似文献   

晚白垩世中国东南沿岸山系与中南地区的沙漠和盐湖化   总被引：25，自引：3，他引：25  

陈丕基 《地层学杂志》1997,21(3):203-213

晚白垩世在中国东南沿古太平洋西岸地区形成了一条巨大的沿岸山系，其山峰高度在３５００—４０００ｍ之间，东西宽度近５００ｋｍ，挡住了东来的暖湿气流，使中南地区云梦泽内陆水域的广大平原和丘陵地变成了一个热带—亚热带干旱、炎热的半沙漠和盐湖地区，这一古地理和古气候格局一直持续到早第三纪末才开始改变。  相似文献   

碳酸锰氧化实验和热力学分析     

郝瑞霞  关广岳 《地质论评》1997,43(2):167-172

通过对碳酸锰氧化实验的结果分析和讨论，建立了一种适合于锰氧化过程的非平衡热力学模型，并利用此模型对硫酸锰氧化过程作了热力学可行性分析，研究结果表明，碳酸锰氧化过程是矿物组合的变化过程，也是锰自身价态的转为过程，整个过程既存在平衡状态，又存在非平衡状态，是一个不可逆的，多相的复杂反应。  相似文献   

上扬子地台区晚古生代海相碳酸盐岩的碳,锶同位素研究   总被引：79，自引：4，他引：79       下载免费PDF全文

黄思静 《地质学报》1997,71(1):45-53

未经蚀变的海相碳酸盐岩的碳，锶同位素组成代表了原始海水的同位素组成，在确定样品末经显著蚀变的基础上，本文测定了上扬子地区晚古生代７条剖面２３８个海相碳酸盐岩样品的碳、锶同位素组成，分布了它们的测试结果和演化曲线，为其他相关研究提供了可利用的基础参照数据。  相似文献