六盘山盆地东部炭山地区下白垩统砾岩层位归属及地层对比新认识

六盘山盆地早白垩世地层称为六盘山群,由下至上划分为三桥组、和尚铺组、李洼峡组、马东山组和乃家河组,其中三桥组由紫红色砾岩组成。位于六盘山盆地东部的固原炭山剖面是六盘山盆地白垩系重点研究剖面,该剖面下白垩统六盘山群下部含有一套厚度为28.0 m的砾岩,以往一直归为三桥组,但本套砾岩的基质或填隙物为灰绿色,与三桥组的砾岩的基质或填隙物为紫红色明显不同,通过结合地震剖面地层解释和沉积演化规律研究,新确定了炭山下白垩统剖面的砾岩层位为李洼峡组边缘相,本剖面缺失六盘山群下部的三桥组、和尚铺组。

The Conqlomerates Adscription and a new Acquaintance of the Lower Cretaceous Stratigraphic Correlation in the Tanshan Region in the East of the Liupanshan Basin

The Early Cretaceous strata of Liupanshan Basin are known as Liupanshan Group, divided into the Sanqiao Formation which consists of red purple conqlomerates, Heshangpu Formation, Liwaxia Formation, Madongshan Formation and Naijiahe Formation from bottom to top. The Tanshan section in Guyuan located in the east of the basin is one of the most study sections in the Cretaceous Liupanshan Basin. There is a set of thick about 28m conqlomerate which were ascribed to Sanqiao Formation in the bottom of Liupanshan Group in this section. The celadon matrices or interstitial materials of the conqlomerates, however, are obviously different from the red purple ones from Sanqiao Formation. Therefore, the conqlomerates in the Lower Cretaceous Tanshan section are newly belonged to the margin facies of Liwaxia Formation by combining the interpretation to seism sections and the research of the sedimentary evolution pattern. There are no sedimentaries of Sanqiao and Heshangpu Formations in this section.