巴西中部元古代Paranoá和Bambui群叠层石的古生态和构造背景

叠层石的形态和它们与陆源沉积的关系反映了沉积盆地的构造背景.在巴西中部地区,叠层石出现在中元古和新元古代的Paranoa群、Vazante群和Bambui群.根据沉积学和矿物学的研究分析,Paranoá群形成于被动边缘盆地,而另外两个群形成于前陆盆地.Vazante群沉积在形成巴西褶皱带的山脉附近,然而Bambui群的大部分都形成于克拉通地区.通常远离山脉褶皱带的Paranoá群和B2mbuí群内的叠层石建造的形态和规模的改变与环境的变化有关.在柱状生长方向的频繁变化和不规则的丰富陆源物质的夹层进入叠层石,表征活跃的构造背景,例如在Vazante,Paranoá群和Bambuí群的西部.

PROTEROZOIC STROMATOLITES FROM CENTRAL BRAZIL: PALAEOECOLOGICAL AND TECTONIC SETTING IN PARANOA AND BAMBUI GROUPS

Stromatolite morphologies and their terrigenous sediment association indicate depositional basin tectonic gin basin (Dardenne & Faria, 1986), while the other two groups represent a foreland basin (Guimaraes, 1993,1997, 1998, Dardenne et al. , 1998). The sediments of the Vazante Group were deposited near the mountain which forms the Brasilia Fold Belt; however, most of the area of Bambui Group originated in a cratonic region. Generalstromatolite buildings are associated with variations in environmental conditions. However, very often changes in the columnar growth direction and irregular terrigenous-rich intercalations into stromatolites characterize tectonically active settings such as in Vazante Group and in the western portion of the Paranoa and Bambui groups.