云南省南涧地区下白垩统南新组砾岩层 砾组特征及其物源意义

该文通过对哀牢山构造带西侧云南省南涧地区下白垩统南新组砾岩层的砾性、砾度、砾态和砾向等的详细研究与分 析，结合盆地基岩地层特点和周边构造带的岩性组合特征，发现南新组砾岩总体上具有砾石成分复杂、分选性较差、磨圆程 度中等-较好（次圆状-圆状）、风化程度较低等特征；探讨了砾岩层本身的性质、物质来源，以及砾石沉积时盆地的水动力条 件、气候环境、古地貌特征和构造条件。认为南新组砾岩层为半干旱-干旱古气候条件下的一套冲积扇-辫状河相粗碎屑沉 积，具有快速堆积的特点；砾岩层沉积前砾石遭受了较强的物理化学作用。根据盆地基岩及周边地层岩性特点和砾石扁平面 倾向统计，砾石的主要来源是盆地内部的基底地层及其东缘的哀牢山构造带。

Gravel Fabric Characteristics of the Lower Cretaceous Nanxin Formationin the Nanjian Region,Yunnan Province and the Provenance Significance

Based on the detailed study of gravel fabric characteristics of conglomerate layers from the Lower Cretaceous Nanxin Formation in the Nanjian region, combined with the characteristics of the basin bedrock stratigraphy and lithologic characteristics of the surrounding tectonic belt, the gravel has complex composition, poor sorting, medium-good roundness and poor degree of weathering. This paper further discussed the property of the conglomerate layer, the material sources and the hydrodynamic conditions, climate, topography and tectonic setting. Our data shows that of Nanxin Formation were the coarse clastic products of alluvial fan and braided river facies in a semiarid to braided climate condition with rapid accumulation; The gravel pebbles suffered a strong physical and chemical weathering before deposition; The sediment source of the gravel was inferred to come mainly from the basal strata within the basin and the Ailaoshan tectonic belt to its eastern direction.