Mundil (2004) suggests there are three scenarios to explain the mass extinction: a bolide impact, catastrophic climate change caused by volcanism or mass methane release. Bowring (1998) even suggests maybe all 3 occurred at once. Siberian volcanism is shown to be synchronous with the P-T extinction, and so Mundil believes it to be most likely. Succession found in quarries at South China (Meishan period) have been the source of much data used to try and explain the mass extinction event and its causes. Isotopic data combined with biomarker data both gathered from Meishan-1 core both show significant ecological disturbance and biogeochemical change that predates the fauna transition therefore marking the Permian Triassic boundary, and helping to explain why the extinction event took place. One scenario put forward by Cao (2009) used to explain the cause of the PTB event is the eruption of the Siberian flood basalts triggering oceanic and atmospheric disturbances which had a significant impact on marine fauna and other life. Black (2014) suggests these mass volcanic releases would have resulted in acid rain leading to the extinction. This theory is seen as highly sound due to the volcanic event occurring from the Siberian traps being one of the largest known volcanic events in the last 500 million years, and coinciding with the P-T extinction. PTB biomarker studies are also used as a tool in an attempt to explain the mass extinction event. Redox sensitive biomarkers suggest the presence of a superanoxic conditions during the time of the PTB event which especially affected shallow marine environments, again hinting to a cause of the PTB extinction (Cao 2009).