摘要
根据苏、皖北部震旦纪叠层石的外形、大小、颜色及纹层特征,结合其它沉积构造特征,探讨水体能量、光照及沉积作用等环境因素对叠层石生长的影响,以此找出叠层石上具有指相意义的某些生态学特征。目前发现,大型层状、层柱状叠层石往往与浅水低能沉积物共生;分叉不发育的大、中型柱状叠层石则与具周期性变化的浅水高能沉积物共生;分叉发育的柱状叠层石与变化不定的浅水高能沉积物共生;平行分叉的小型柱状叠层石则与中-次中等能量沉积物共生。值得注意的是,环境的变化使一些叠层石形态也随之变异,形成一系列过渡类型,引起分类上的混淆。叠层石纹层表面积与水深往往成反比梯变,这也许与藻席受光照的充足程度有关。叠层石及其围岩的原生色也可作为了解当时水体化学性质及生物对矿物的富集作用的线索。
Results of research on algal stromatolites from the Sinian of northern Jiangsu and Anhui, China, suggest that their morphological characteristics indicate some ecological elements such as water energy, illumination and sedimentation, which could influence the formation of stromatolites. It is believed that stromatolites with certain morphological characteristics were located in a certain environment.
Large-sized layered or columnar-layered stromatolites, for example, occupied low energy shallow waters; large- or medium-sized nonbranching columnar stromatolites appeared frequently in turbulent high energy shallow waters where the change in turbulence and the quantity of supplied sediments were steady and periodical; divergent-branching columnar ones occurred in high energy shallow waters with unstable change in turbulence and currents in all directions; medium- or small- sized parallel-branching columnar ones occurred in slightly unrestful sub-medium energy waters; while the stromatolites elongated through a certain level direction occurred in a strong current running toward a certain direction. It merits our attention that morphological interfusion between two groups of stromatolites varied with the environment.
Moreover, the surface area of a stromatolitic laminate was inversely proportional to the water depth, i. e., the more plentiful the sunlight, the bigger the area of the algal mat; on the contrary, the less the sunlight, the smaller the area of the algal mat.
The original colour of stromatolites and country rocks was closely related to paleochemical environment and mineral collection by algae. The dark laminates of some stromatolites, for example, appeared in red-purple colour, with the country rocks in yellow-brown colour, and therefore, it is quite evident that the algae collected Fe^(3+) in their life activity under an acidic oxygenated condition. The dark laminates of other ones were green, with the country rocks in green-yellow colour; they were both rich in glauconites, suggesting a slightly oxygenated to slightly reductive environment with a slow sedimentation process, a pH value of 7—8, a water temperature <15℃, and rich in K, Fe and organic substances.
To sum up, the large- or medium-sized layered, columnar-layered and columnar stromatolites frequently occurred in the intertidal zone, such as Stratifera, Conophyton, Jurusania, Linella. Tungussia, Anabaria, etc.; the medium- or small-sized columnar ones often occurred in the intertidal- subtidal zone, such as Jurusania, Kussiella, Boxonia, Inzeria, Gymnosolen, Katavia, etc.; while th small-sized columnar and spherical ones usually occurred in subtidal or deeper water zone
出处
《古生物学报》
CAS
CSCD
北大核心
1991年第5期616-629,675-677,共14页
Acta Palaeontologica Sinica
关键词
叠层石
震旦纪
沉积环境
Stromatolites in Sinian period, environment, northern Jiangsu and Anhui
