摘要
天山晚白垩世—新生代沉积序列中发育 K2 / K1 、N1 / E3以及 Q2 / Q1 3个重要不整合面 ,它们作为重要的界面并结合沉积相序组合的发育 ,共划分出 TC- 0至 TC- 7等 8个向上变粗、变浅的巨型沉积层序 ;砂岩碎屑模型分析表明 ,南、北天山物源构造属性有别 ,分别来自南北侧再旋回造山带或切割—未切割岩浆弧 ;砂岩组分和重矿物组合显示渐新世—早中新世间物源区曾发生过明显的改变 ,耦合于天山造山带沉积 -构造演化 ;造山带内批量磷灰石裂变径迹年龄呈现出频率较高的几个年龄组段 ,即频率 4 8.84 %的 2 4 .74 Ma、频率 2 7.91%的 15 .98Ma和频率 11.6 3%的 4 5 .2 2 Ma,从而确定了天山初始隆升及其后的几个主要隆升阶段的时限 ,即白垩纪末期—始新世 (6 5 .6～ 4 5 .2 2～ 32 .6 0 Ma)的初始隆升以及 2 4 .74～ 15 .98Ma、小于 6 .7Ma大于 0 .73Ma和小于 0 .73Ma等至少 4个隆升时期 ;造山带隆升的年龄数据除部分和地层中磨拉石建造发育的年代基本吻合外 ,大多磨拉石建造年代增新约 8～ 1Ma,反应了天山造山带边缘盆地内沉积层序发育和造山带形成演化间的耦合—滞后关系 ;天山最初的隆升时限为晚白垩世 ,渐新世末期北缘较南缘先期发育 ,同时北缘西段较东段表现强烈 ,上新世—早更新世时期隆升才向土哈盆地和?
Eight huge depositional successions from TC-0 to TC-7, which are dominantly shollowing and coarsening upward, have beeb recognized based upon 3 disconformable surfaces as K 2/K 1, N 1/E 3 and Q 2/Q 1 and sedimentary facies associations in the Late Cretaceous—Ceonozoic deposits in the Tianshan areas. Sandstone detrital model analysis indicates that the Mesozoic and Cenozoic sediments are characterized by different provenances such as the recycled orogen, undissected and magmatic arc. The compositions of sandstones and dense (heavy) minerals and their associations in the sandstones reflect a change in provenance between the Oligocene and Early Miocene, which is coupled with the depositional-tectonic evolution of the Tianshan. The apatite fission-track data show several major frequency clusters as 24.74 Ma at 48.84%, 15.98 Ma at 27.91% and 45.22 Ma at 11.63%, which are interpreted as the uplifting age intervals of the Tianshan. The ages of 65.6 Ma, 45.22 Ma and 32.60 Ma maybe considered as the initial unroofing ages, together with the intervals of 24.74～15.98 Ma, 6.7～0.73 Ma and < 0.73 Ma they represent the four major uplifting ages. Most of the ages of the molass formations are 8～1 Ma younger than the apatite fission-track ages of orogenic rocks, with only a few data being correlative, which reflects that there exists a depositional delay and coupling relationship between the orogenic evolution and the deposition whithin marginal basins. This study suggests that the initial uplifting of the Tianshan started in the Late Cretaceous. In the terminal Oligocene, the northern margin was developed earlier than the southern one, and the western parts of the former experienced more rapid uplifting than the eastern one. It was not until the Pliocene—Early Pleistocene that the uplifting shifted southward to the Turpan-Hami basin and the southern Tianshan.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2004年第3期319-331,共13页
Acta Geologica Sinica
基金
国土资源部地质调查局"中国西部典型造山带研究 (编号 2 0 0 113 0 0 0 0 2 2 )"
"东准噶尔南缘中新生代造山过程及盆山耦合研究(编号 DKD2 10 10 2 5 )"项目资助的成果
关键词
沉积序列
年代学
地质演化
隆升
Tianshan
uplift
deposition
chronology
evolution
