广东河源盆地红层的初步研究

PRELIMINARY STUDY OF THE RED BEDS IN THE HEYUAN BASIN OF GUANGDONG

河源盆地红层厚达 5 0 0 0 m,依岩性特征自下而上划分为大凤组、主田组、浈水组、丹霞组和莘庄村组。前三组称南雄群 ,粗碎屑岩较发育 ,厚 16 0 0— 370 0 m。大凤组为紫红、暗紫红色砾岩 ,在盆地北部该组上部为细砾岩夹含砾砂岩 ,富产恐龙圆形蛋化石 ,厚 5 6 7m;主田组为紫红色含砾砂岩与不等粒砂岩互层夹细砾岩、砂质泥岩 ,富含灰质结核 ,产窃蛋龙、恐龙长形蛋、龟鳖类、腹足类和瓣鳃类化石 ,厚 90 0 m;浈水组沉积物又较粗 ,以细砾岩、含砾砂岩发育为主要特征 ,厚达 2 2 0 0 m。大凤组和主田组富含恐龙蛋化石 ,其面貌与南雄盆地相似 ,时代属晚白垩世无疑。丹霞组全为粗碎屑岩 ,为紫红色块状砾岩、砂砾岩 ,具丹霞地貌特征 ,厚 70 0 m,时代暂归晚白垩世—古新世。莘庄村组以红色细碎屑岩发育、富含灰质结核、下粗上细、上部红黑相间为主要特征 ,产介形虫、轮藻、腹足类、瓣鳃类化石 。

Red beds in the Heyuan Basin reach as much as 5 000m thick, and are divisible in ascending order into the Dafeng, Zhutian, Zhenshui, Danxia and Xinzhuangcun Formations based on lithologies. The first three formations are collectively known as the Nanxiong Group where coarse clastic rocks are well developed with thicknesses varying beween 1 600m and 3 700m. The Dafeng Formation, 567m in thickness, consists of purplish red and dark purplish red conglomerate, but in the northern part of the basin it turns out to be a fine grained conglomerate with gravel bearing sandstone in the upper part, with abundant fossil dinosaurian eggs of Oolithes spheroides type. The Zhutian Formation, 900m in thickness, is composed of interbedding purplish red gravel bearing sandstone and heterogranular sandstone intercalated with fine grained conglomerate and sandy mudstone, rich in limy concretions, and with egg stealing dinosaurs, dinosaurian eggs of Oolithes elongatus type, turtles, gastropods and bivalves. The Zhenshui Formation, up to 2000m thick, with rather coarse sediments, are characterized largely be the development of fine grained conglomerate and gravel bearing sandstone. The Dafeng and Zhutian Formations are rich in dinosaurian eggs and are similar in appearance to those red beds in the Nanxiong Basin, hence can no doubt be ascribed to Late Cretaceous age. The Danxia Formation, 700m thick, are made up entirely of coarse clastic rocks including purplish red massive conglomerate and sandy conglomerate, displaying the features of a Danxia landform. Its age is temporarily attributed to the Late Cretaceous—Paleocene. The Xinzhuangcun Formation is characterized chiefly by the development of red fine clastic rocks, containing rich limy concretions, coarse in the upper but fine in the lower part in grain size, and displaying alternating red and black color in the upper part. This formation contains ostracods, charophytes, gastropods and bivalves, and is Paleocene in age.