海拉尔盆地乌南次凹南屯组层序格架及沉积体系研究

以层序地层学、坡折带分析理论为指导，通过对岩心、测井、录井、地震以及分析化验等资料的综合研究，建立了海拉尔盆地乌南次凹南屯组层序地层格架。将南屯组划分为 2 个三级层序和 8 个四级层序，并在层序格架内进行沉积体系和沉积相划分研究，确定该区主要发育近岸水下扇、扇三角洲、湖底扇和湖泊沉积等 4 种沉积体系。近岸水下扇主要分布在乌南次凹西部陡坡带，扇三角洲分布在东部缓坡带，湖底扇主要分布在中心的深湖相中，而湖泊沉积主要分布在凹陷的中心及近岸水下扇、扇三角洲的侧翼。从乌南次凹西部断阶带到凹陷中心，沉积相由近岸水下扇逐渐变为深湖--半深湖沉积，乌南次凹东部缓坡带到中心，沉积相由扇三角洲沉积逐渐变为滨浅湖、深湖--半深湖沉积，整体呈南北分异、东西成带的格局。不同时期的沉积特征、沉积相展布表现各异，总体表现出水体由浅变深，再变浅，沉积范围逐渐扩大的特点。

Research on stratigraphic framework and sediment system in Nantun Formation of South Wu Sag in Hailaer Basin

Guided by the theories of sequence stratigraphy and rupture zone analysis, the stratigraphic framework of Nantun Formation of South Wu Sag in Hailaer Basin, based the authors recognized on integrated study of core, logging, mud-logging, seismic and its test data. Nantun Formation is divided into two third-order sequences and eight fourth-order sequences. The sediment system and sediment facies were studied under the stratigraphic framework, and four sediment systems （underwater fan near the coast, fan delta, turbidite fan and lake） were de- termined. The underwater fan near the coast mainly distributed on the western abrupt slop of South Wu Sag, fan delta mainly distributed on its eastern gentle slope, turbidite fan mainly distributed in deep lake facie of its center, and the lake mainly distributed in the center of South Wu Sag and on the both sides of underwater fan and fan del- ta. The underwater fan near the coast facies changed of South Wu Sag; the fan delta changed graduall slight grade to the center of South Wu Sag. All to deep or semi-deep lake from western fault zone to the center y to beach shallow lake and deep or semi-deep lake from eastern these sediments distributed entirety differently along north-south, and constituted band zone along east-west direction changed everywhere, exhibitting the water changed During the geologic time, the distribution of sediment facies from shallow to deep, and then became shallow again, and the areas of sedimentations gradually expanded.