藏北羌塘南部发现早古生代地层及意义

程立人; 陈寿铭; 张以春

藏北羌塘南部发现早古生代地层及意义

1.
吉林大学地球科学学院, 吉林长春 130061
2.
中国科学院南京地质与古生物研究所, 江苏南京 210008

基金项目:

中国地质调查局区域地质调查项目 200313000015

详细信息

作者简介:
程立人(1954-), 男, 副教授, 主要从事地层古生物学的教学与研究. E-mail: chenglr@jlu.edu.cn

中图分类号: P539
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出版历程
- 收稿日期: 2006-04-11
- 刊出日期: 2007-01-25

Discovery of Early Paleozoic Strata in South of Qiangtang, Northern Tibet and Its Significance

1.
College of Earth Science, Jilin University, Changchun 130061, China
2.
Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China

摘要

摘要: 藏北羌塘南部地区沿龙木错-双湖缝合带南侧发育大面积的变质岩系, 此前统称为阿木岗群.由于没有发现古生物化石, 时代归属争议很大.有人依缝合带以北查桑地区有未变质的含古生物化石泥盆系出露为据, 将该套变质岩系时代归属前泥盆纪, 多数人是根据所测同位素年龄值, 确定其时代为前震旦系.2003—2004年我们在玛依岗日一带变质岩系上部采获大量鹦鹉螺类和笔石类化石, 经研究确定时代属中、晚奥陶世-志留纪.在羌塘南部地区发现有可靠化石依据的早古生代地层存在尚属首次.为该岩系的时代归属、地层划分及与邻区对比提供了古生物证据, 也为研究该区岩相古地理、大地构造格局提供了可靠资料.
- 藏北 /
- 羌塘南部 /
- 早古生代地层 /
- 鹦鹉螺 /
- 笔石
Abstract: Due to the lack of fossil evidence, the age of Amugang Group, previously referring to the large area of metamorphic formations developed along the south of Longmucuo-Shuanghu suture in southern Qiangtang area, northern Tibet, has been under heated debate. Some geologists were convinced that the age of metamorphic formations was of Pre-Devonian according to the emergence of nonmetamorphic fossil-bearing Devonian in Chasang area, north of the suture. Most geologists believed that its age was of Pre-Sinian. From 2003 to 2004, we collected a large amount of Nautiloid and Graptolite fossils in upper metamorphic formations of Mayigangri area and determined the age to be middle and Late Ordovician-Silurian. It is the first time to discover the Early Paleozoic strata based on reliable fossils, which not only provides evidence to its age ascription, classification of the strata and its correlation to adjacent areas but also offers data to lithofacies, palaeogeography and tectonic pattern of studied area.
- northern Tibet /
- southern Qiangtang /
- Early Paleozoic strata /
- Nautiloid /
- Graptolite

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图 1 研究区位置图

Fig. 1. location map of the study area

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图 2 羌塘南部塔石山上早古生代实测剖面图

Fig. 2. Section of Early Paleozoic strata in southern Qiangtang

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图 3 部分化石野外照片

1, 5.Michelinoceras paraelongatum.1.自然风化面, ×0.9, 采集号: P₁₄H_13-2, 登记号: 04Chy-02;5.自然风化面, ×0.8, 采集号: P₁₄H_13-10, 登记号: 04Chy-10, 采集层位: 羌塘南部古生界中上奥陶统; 2.Michelinoceras sp., 自然风化面, ×1, 采集号: P₁₄H_16-2, 登记号: 04Chy-39, 采集层位: 羌塘南部古生界中上奥陶统; 3, 6, 7.Sinoceras sp., 3.自然风化面, ×1, 采集号: P₁₄H_13-8, 登记号: 04Chy-08;6.自然风化面, ×1, 采集号: P₁₄H_19-2, 登记号: 04Chy-57;7.自然风化面, ×1.5, 采集号: P₁₄H_17-12, 登记号: 04Chy-40, 采集层位: 羌塘南部古生界中上奥陶统; 4.Michelinoceras?huangnigangense, 背腹纵切面, ×1, 采集号: P₁₄H_13-19, 登记号: 04Chy-19, 采集层位: 羌塘南部古生界中上奥陶统; 8, 9.Monograptus sp., 8.自然层面, ×1, 采集号: P₁₄H_22-2, 登记号: 04Chb-02;9.自然层面, ×1, 采集号: P₁₄H_22-10, 登记号: 04Chb-10, 采集层位: 羌塘南部上古生界志留系; 10.Pristiograptus sp., 自然层面, ×1, 采集号: P₁₄H_22-7, 登记号: 04Chb-07, 采集层位: 羌塘南部上古生界志留系; 11.Climacograptus sp., 自然层面, ×1, 采集号: P₁₄H_22-19, 登记号: 04Chb-19, 采集层位: 羌塘南部上古生界志留系

Fig. 3. Field photograph of some fossils

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