| 摘要: |
| 藏南洛扎地区侏罗、白垩纪处于印度板块被动边缘一侧,共划分9个沉积相带、9个沉积亚相。日当组由南而北,海水由浅变深,可划分3个相带;陆热组总体处于陆棚环境;遮拉组处于陆棚—深海盆地环境,沿绒布断裂以北,发育拉张环境下的中—基性火山岩,总体沿断裂一带呈中心式喷发,其沉积背景为深水盆地相,发育放射虫硅质岩等;维美组为深水背景,在硅质岩、泥质沉积的陆棚—盆地区,有浅水物质的夹层,发育深切河谷的水道沉积物与浊流沉积物共存现象,并对下伏地层产生强烈的下切;桑秀组区内再次表现为强烈的伸展拉张,绒布断裂可能初现,沿断层发育中心式的中—基性火山喷发,出现火山爆发角砾、枕状熔岩、柱状节理发育的安山岩,并在断裂北侧形成滑塌角砾岩,而南部相对平静,沉积一套陆棚相的泥质沉积物;甲不拉组显现“一隆两坳”的地貌单元,北侧绒布断裂以北为开阔海陆棚环境,洛扎以南为闭塞湖环境。 |
| 关键词: 侏罗 白垩纪 古地理 洛扎 西藏 |
| DOI： |
| 附件 |
| 投稿时间：2004-12-24修订日期：2005-05-26 |
| 基金项目:中国地质调查局“西藏1∶25万《洛扎幅》区域地质调查”(01999134061)。 |
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| Sedimentary facies and palaeogeography of the Lhozhag region in southern Xizang during the Jurassic and Cretaceous |
| XIA Jun, ZHONG Hua-ming, TONG Jing-song, LU Ru-kui |
(1. Anhui Institute of Geological Survey, Hefei 230001, Anhui, China;
2. China University of Geosciences, Beijing 100083, China;
3. Northwest China University, Xi'an 710069, Shaanxi, China) |
| Abstract: |
| Nine sedimentary facies and nine sedimentary subfacies have been distinguished for the Jurassic and Cretaceous strata in the Lhozhag region,southern Xizang.From south to north,the sea water becomes progressively deeper in the Ritang Formation,where three facies belts may be recognized.The Lure Formation lies totally in the shelf environment,and the Zhela Formation in the shelf and deep-sea basin environments,where there occur the intermediate and basic volcanic rocks in the extensional settings north of the Rongpu fault and radiolarian siliceous rocks in the deep-sea basin facies.In the Weimei Formation in the deep-water environment,there exist the siliceous rocks and muddy sediments intercalated with shallow-water sediments in the shelf-basin zone,and the coexistence of incised valley deposits and turbidity current deposits.The intense extension and intension once took place in the Sangxiu Formation.The intermediate and basic volcanic eruption along the Rongpu fault brought about diatreme breccias,pillow lavas and andesite with developed prismatic joints and slump breccias on the northern side of the fault while on the southern side of it,there deposited a succession of shelf muddy sediments.The geomorphologic framework of "one uplift and two depressions" appears in the Jiabula Formation:the open shelf environment north of the Rongpu fault and restricted lagoon environment south of Lhozhag. |
| Key words: Jurassic Cretaceous sedimentary facies and palaeogeography Lhozhag Xizang |
