摘要
冰期中的全球性冰川事件不仅对全球性海平面变化，而且对低纬陆棚碳酸盐环境的沉积作用也有重要影响。与温暖时期相比，位于低纬度的华南地区在晚震旦世冰期，晚奥陶－早志留世冰期，石炭－二叠纪冰期中记录了相对低的沉积速度和低的环境分异（反映在相的侧向变化很小）。每一段冰期沉积可以被与最大球进所对应的海退面分为两部分。早期的沉积环境以弱咸化和富氧为特征。该环境形成浅色、相对富颗粒的灰岩沉积。随着寒冷气候的侵入，代替暖水碳酸盐的最可能是该界面附近的温带碳酸盐的堆积。该界面之上，随着温度上升和海侵，表面海水出现轻微淡化。水体的密度分层导致形成还原条件。有机质和沥青质使微晶灰岩和富硅的沉积染成灰到黑色。盐度以及还原－氧化条件的变化被认为和两极冰盖的增减有关。与Ｖａｉｌ的二级或三级旋回曲线相对应的３个界面分别相当于冰期的开始、顶峰和消失，反映了全球性冰川事件对二级和三级海平面变化旋回的影响。
World-wide glacial event in an ice age not only contributes to eustatic sea level changes but also penetrates to the shelf carbonate environments and sedimentation coeval low latitude area.Contrasted with those in warm period,relatively low depositional rate and low diversity of environment (indicated by little laternal variation of facies) were recorded in the interval of Late Sinian glaciation,late Ordovician to early Silurian glaciation and Permo-Carboniferous glaciation in South China which located in low latitudes.By a turn,which was indicated by a major regrerssion coinciding with the peak development of glaciation,each of the interval can be easily seperated into two stages. In the early stage,depositional environment was characterzied by slightly salinizing coupled with oxdi conditions.Relatively grain-rich limestone with light-color formed in the environment.Most possibly, instead of warm-water carbonates,the invasion of cool climate might lead the accumulation of temperate carbonates in the region around the turn. After the turn,with the course of warming and transgression, slight freshing took place in surface water.Consequent pycnocline stratification in water column resulted in the prevailing of reducing condition.Organic materials and bituminites dyedthe micrite-and silica-rich deposits grey to black.The variation of salinity cotlpled with that of reduction-oxidation was believed to be related to the waxing and waning of polar ice sheets in spite details leaved to be deciphered.The agreement of the three surfaces (corresponding to the onset,peak development and the collapse of a glaciation respectively) with Vail' s 2-nd order or 3-rd order cycle curve indicates the glacio-eustatic components in the domain of 2-nd order and 3-rd order curve.
出处
《地质科技情报》
CAS
CSCD
北大核心
1994年第3期48-56,共9页
Geological Science and Technology Information
基金
国家基础性重大关键项目SSLC项目
关键词
冰川
碳酸盐
沉积环境
沉积作用
glacial period
shelf carbonate sedimentation of low latitudes
Sedimentation coeval
latest sinian glacial period,late ordovician-early silurian glacial period,Permo-Calrboniferous glacial period
