辽南地区新元古代叠层石全球衰落事件研究

Stromatolite are layered accretionary structures formed in shallow water by the trapping,binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria (commonly known as blue-green algae). Stromatolites provide some of the most ancient records of life on Earth by fossil remains which date back more than 3.5 billion years ago. Stromatolites are a major constituent of the fossil record for about the first 3.5 billion years of life on earth, peaking about 1.25 billion years ago. However, stromatolite decline events occur in geological times for five times.The biggest stromatolite decline events happen in Neoproterozoic.This event is also reciorded in Southern Liaoning Province. They subsequently declined in abundance and diversity,which by the start of the Cambrian had fallen to 20% of their peak. The most widely-supported explanation is that stromatolite builders fell victims to grazing creatures (the Cambrian substrate revolution), implying that sufficiently complex organisms were common over 1 billion years ago. Stromatolite bloom in Shisanlitai Formation, hower in Majiatun Formation after Shisanlitai Formation stromatolite decline.Previous limited data shows the C and O isotope decrease in this transitional times. Until now there are no systematical geochemical studies on this event in China.

叠层石是前寒武纪最为引人注目的生物沉积结构。在新元古代(约距今7亿年左右)，叠层石出现了全球性的衰退事件。Awramik(1971)将新元古代叠层石的衰亡与伊迪卡拉软后生动物的出现相联系，得到Walter和Heys(1985)的支持。然而，伊迪卡拉后生动物的出现(小于600 Ma)与叠层石的衰退之间尚有数亿年的时间间隔，很难将其联系起来。 这一转变事件在国外毛里塔尼亚阿塔尔群研究的比较详细，被认为可能与全球海洋化学条件变化有关。而这一事件，在中国也有很好的体现。中国辽南地区叠层石非常丰富，在新元古代，叠层石从十三里台期向马家屯期面貌发生根本改变，稳定展布的生物层礁为各种形态丘状生物岩礁所替代。但是至今为止中国对此事件还缺乏详细系统研究。 本项目拟对辽南地区的十三里台组及马家屯组进行连续的、高精度的叠层石类型统计、沉积相分析以及碳、氧、锶同位素，阐明叠层石的衰退与背景环境的关联。

叠层石是前寒武纪最为引人注目的生物沉积结构。在新元古代(约距今7亿年左右)，叠层石出现了全球性的衰退事件。Awramik(1971)将新元古代叠层石的衰亡与伊迪卡拉软后生动物的出现相联系，得到Walter和Heys(1985)的支持。然而，伊迪卡拉后生动物的出现(小于600 Ma)与叠层石的衰退之间尚有数亿年的时间间隔，很难将其联系起来。 这一转变事件在国外毛里塔尼亚阿塔尔群研究的比较详细，被认为可能与全球海洋化学条件变化有关。而这一事件，在中国也有很好的体现。中国辽南地区叠层石非常丰富，在新元古代，叠层石从十三里台期向马家屯期面貌发生根本改变，稳定展布的生物层礁为各种形态丘状生物岩礁所替代。但是至今为止中国对此事件还缺乏详细系统研究。. 本项目拟对辽南地区的十三里台组及马家屯组进行连续的、高精度的叠层石类型统计、沉积相分析以及碳、氧、锶同位素，阐明叠层石的衰退与背景环境的关联。