摘要
近年来,笔者在秦一唐地区进行野外工作时,在一些十分理想而又难得的露头上搜集到了一些叠层石群体形态的资料,这些叠层石的群体形态是过去文献资料上未曾有过的,并从沉积学的角度对它们进行了研究,初步探明了这些群体与沉积环境间的依存关系,简述如下: 一=群体形态 1、球柱状:为顶部成半圆形的、上粗下细的柱体,高略大于直径,约1米左右,柱体系由一系列“叠层石层”的完整包壳迭覆而成,球柱体成群出现,其间距不等。 2、燧道状:断面成拱形,有时上宽而下窄,由底至顶均为密集的柱状叠层石,每一群体顶部有一拱形的盖,断面高0.3—1.2米,长7米左右,“燧道”成群出现,其间距不等。 3.球冠状:由多层“叠甚石层”组成,每一“叠层石层”成一弧形,弧与弧边缘相互叠压,顶部构成一个大穹降状,穹降高3—4米,长10—15米,穹隆相连成层状。二、沉积环境分析根据沉积构造及对叠层石群体间填隙物的成分、形态、分布状况等研究,初步判断群体 1 形成於高能环境;群体2形成於中等能量的环境;而群体3形成於低能环境。从群体进行叠层石形态的描述和环境分析尚属探索,笔者正进行更详细的工作,以期获得更多的资料来丰富这一研究内容。
During the field works carried out recent years in Northen China, the authors found some ideal outcrops of stromatolites with several particular kinds of colonial forms which had not been reported in the previous literatures. These colonial forms have been studied sedimentologically by the authors and some preliminary conclusions on the interdependent relationship between colonies and their sedimentary environments have been worked out, which were briefly shown as following: A、Colonial forms ' 1. Sphero-columnar: Semicircle on the top. Columnar bodies are gradually thickened from the floor to the top. About one meter in height which is slightly greater than diameter. Composed of a series of 'strnmatolite layers' with complete coated crusts and occur as groups. The distances between the individual bodies are unequal. 2. 'Tunnel-like': Arch shaped in cross section. Some are wider upward while narrower downward. Composed wholly of the concentrated collumaaefacta. The top of every colony forms an arch cap. About 0.3 to 1.2 meters in height, 7 meters in length. Other features are the same as sphero-columnar. 3. Spherical crown shaped: Consist of multiple 'stromatolite layers'. Every layer shown as an arch. The arches overlap each other in the fringes forming a large dome at the top with a height of 3 to 4 meters and a length of 10 to 15 meters. Many domes conjoin into a layer. B、Analysis of the sedimentary environment According to the studies of sedimentary structures, filling compositions between the colonies of stromatolite, their forms and distribution pattern and so on, the authors put forward a preliminary conclusion that the colonial form 1 was formed in a high energy environment, form 2, amiddle energy and form 3, a low energy. Both describing stromatoliie forms and analysing their formative environments in respect of colonies are only explorative, and more detailed works are being carried on by the authors for enriching the contents of this research.
