摘要： 鄂尔多斯地区早古生代沉积了一套以海相碳酸盐岩夹碎屑岩为主的沉积建造，沉积厚度巨大，沉积类型多样，可以划分为海岸沉积、碳酸盐岩台地沉积、台地边缘沉积和深水斜坡—海槽沉积4大沉积类型以及数个亚相和微相，并对各个沉积相带的沉积特征和时空展布进行了归纳和总结。在此基础上，编制了早古生代岩相古地理图1套。岩相古地理研究表明，早寒武世仅在鄂尔多斯西南缘环陆发育了一套泥砂坪、泥云坪沉积；中寒武世海侵扩大，广大的鄂尔多斯中东部逐渐由砂泥坪发展为局限—开阔台地沉积，在其西缘发展为台地边缘—深水海槽沉积；晚寒武世开始海退，中东部主体演变为局限台地云坪沉积，而西侧的深水斜坡—海槽则继续发育。早奥陶世鄂尔多斯主体为一古陆，仅在东南缘形成环陆泥云坪和云灰坪相沉积；中奥陶世的大规模海侵使鄂尔多斯大部地区形成了广阔的浅水陆表海沉积，在陕北凹陷发育膏盐湖沉积，向外依次发育局限台地和开阔台地沉积，中奥陶世晚期西南侧开始发育台地前缘斜坡—深水海槽沉积；晚奥陶世的加里东运动使鄂尔多斯整体抬升为陆，仅在西南缘的狭窄海域接受沉积，由碳酸盐岩台地很快过渡为深水斜坡—海槽沉积，并在南缘发育生物礁建造，形成陆缘海型镶边台地沉积。

关键词: 岩相古地理, 早古生代, 鄂尔多斯, 寒武纪, 奥陶纪

Abstract: A set of marine carbonate rocks interbedded with clastic rock was deposited in the Early Paleozoic in the Ordos area，with huge thickness and various sedimentary types.According to characteristics of sedimentary sequence，petrology，sedimentary structure and palaeontology，four depositional systems can be distinguished in the Lower Paleozoic in the Ordos including coast，carbonate rock platform，platform margin and deepwater slope-trough，which can be subdivided into several subfacies and microfacies.For each facies，its sedimentary characteristics，spatial and temporal distribution were summarized.Based on these studies，the lithofacies palaeogeography maps of the Lower Paleozoic in the Ordos were compiled by each age.The Early Cambrian only formed a set of mud-sand flat and mud-dolostone flat sediments around the southwestern margin of the Ordos land.Followed the marine transgression spread in the Middle Cambrian，the central-eastern part of the Ordos was gradually transformed from sand-mud flat to restricted platform-open platform sediments，and developed platform edge to deepwater trough sediments in the western margin.Since the Late Cambrian marine regression，the central-eastern part of the Ordos was changed to restrictive platform dolostone flat sediments，but the deepwater slope-trough facies was still developed in the western margin.To the Early Ordovician，the main body of the Ordos became a uniform palaeoland with mud-dolostone flat and dolomitic-limestone flat sediments around its southeastern margin.Then a massive transgression in the Middle Ordovician led to an extensive shallow epicontinental deposits in the Ordos.The Northern Shaanxi Depression formed a gypsum salt lake，and developed restrictive platform-open platform sediments outside it.At the late Middle Ordovician，the southwestern margin began to develop platform foreslope-deepwater trough facies sediments.The Late Ordovician Caledonian Movement uplifted the main Ordos as a land，and formed a narrow sea continuing deposit in the southwestern margin of the Ordos.The sedimentary facies was quickly changed from carbonate rock platform to deepwater slope-trough，and developed some reefs in the southern margin of Ordos，indicating the epicontinental marginal rimmed platform deposit.

Key words: lithofacies palaeogeography, Early Paleozoic, Ordos, Cambrian, Ordovician

中图分类号: 

• P531