Determining the nature and drivers of Earth's first metazoan radiation and subsequent extinction: The Cambrian 'Explosion' and Sinsk Event

大约5.4亿年前（Ma）开始的寒武纪辐射，标志着化石记录中丰富多样的动物（后生动物）的出现。这种辐射可能是由振荡的海洋氧合和生产力事件驱动的，但被第一次大灭绝，即大约513 Ma的“辛斯克事件”所终止。辛斯克事件被认为是一个广泛的海洋缺氧的高温期，它重置了所有后来的后生动物生命的轨迹。然而，尽管它对地球的宜居性和复杂生命的进化过程具有重要意义，但人们对这一事件的驱动因素知之甚少，也不知道哪些环境因素控制了灭绝的选择性。我们假设是低的海洋硫酸盐水平促进了振荡氧合，因此产生了脉冲后生动物辐射，但矛盾的是，这也使寒武纪早期的浅海极易受到全球变暖的缺氧影响，从而以一场深刻的灭绝来终止这些辐射。我们提出了一种雄心勃勃的综合古生物学，地球化学和建模方法来解开辐射的控制过程，以及神秘但非常重要的Sinsk事件的后果。通过比较寒武纪辐射和寒武纪灭绝的驱动因素，我们将解决一个基本的激励问题：在地球历史上，低硫酸盐海洋是否既促进了辐射，又导致了物种灭绝？

The Cambrian Radiation, starting ca. 540 million years ago (Ma), marks the appearance of abundant and diverse animals (metazoans) in the fossil record. This radiation may have been driven by oscillating ocean oxygenation and productivity events, but was terminated by the first mass extinction, the 'Sinsk Event', ca. 513 Ma. The Sinsk Event is considered to have been a hyperthermal interval of widespread ocean anoxia that reset the trajectory for all subsequent metazoan life. However, despite its significance for the course of Earth's habitability and the evolution of complex life, little is known about the drivers of this event, or which environmental factors controlled extinction selectivity. We hypothesise that it was low oceanic sulphate levels that promoted oscillating oxygenation, so creating pulsed metazoan radiations, but paradoxically this also made the early Cambrian shallow ocean highly susceptible to anoxia in response to global warming, thereby terminating these radiations with a profound extinction. We propose an ambitious integrated palaeobiological, geochemical and modelling approach to unravel the controlling processes of radiations, and the consequences of the enigmatic, but highly significant, Sinsk Event. By comparing the drivers of the Cambrian Radiation with those of its demise, we will address a fundamental motivating question: Did low sulphate seas both promote radiations and drive extinctions through Earth History?