Oceanographic and Biotic Changes in Australia During Cretaceous Oceanic Anoxic Events

在中生代，地球经历了一系列罕见的突发和短暂的海洋缺氧事件（oae），其特征是严重的全球变暖，可能是由火山脱气引起的。尽管它们对了解地球-海洋-大气系统很重要，但oae的环境影响和因果机制尚未得到充分解决，特别是在记录极其有限的南半球，人们对其了解甚少。其中最大的事件之一是在Cenomanian-Turonian边界（~94 Ma）发生的OAE2，它与火山作用、突然变暖、增加的水文循环、海洋的营养供应、高生产力和海洋生物群的大规模灭绝有关。本项目旨在首次重建澳大利亚西南部在OAE2之前、期间和之后的古海洋学和植被，并独家获得国际海洋发现计划（IODP） 369考察期间收集的新核心材料。本项目旨在研究全球气候变化对澳大利亚西南部白垩纪古海洋学、古气候和生物进化的短期和长期影响。该学生将利用沉积有机地球化学GDGTs（包括TEX86海水表面温度代理）重建白垩纪期间的变化，特别关注OAE2。目前缺乏来自南部高纬度地区的数据（Jenkyns et al. 2012），因此该项目将测试OAE2高纬度地区变暖的程度，并寻找短期变化的证据，例如北半球OAE2内发生的“正气冷事件”（Zheng et al. 2013）。利用鞭毛藻囊组合重建局部生产力变化，以研究OAE2和更长期白垩纪的海洋上升流和陆源营养输送。该项目还将通过生成白垩纪晚期的花粉粒和孢子记录，以及OAE2上的高分辨率记录，评估与水文循环相关的区域植被变化。最近在澳大利亚西南海岸IODP 369考察期间收集的原始新沉积物岩心（Hobbs et al. 2016）是有机地球化学和孢粉学分析的理想选择，因为它们热未成熟且埋藏深度低。

During the Mesozoic, Earth experienced a rare series of abrupt and short-lived episodes of Ocean Anoxic Events (OAEs), characterised by severe global warming and possibly triggered by volcanic degassing of CO2. Despite their importance for understanding the Earth-ocean-atmosphere system, the environmental impacts and causal mechanisms of OAEs have yet to be fully resolved, and are particularly poorly understood in the southern hemisphere where records are extremely limited. One of the largest such events, OAE2 at the Cenomanian-Turonian boundary (~94 Ma), has been associated with volcanism, abrupt warming, an increased hydrological cycle, nutrient supply to the oceans, high productivity, and mass extinctions in marine biota. This project aims to reconstruct palaeoceanography and vegetation of southwest Australia before, during and after OAE2 for the first time, with exclusive access to new core material collected during International Ocean Discovery Program (IODP) Expedition 369.The aims of this project are to investigate both the short and long term impacts of global climate change on Cretaceous palaeoceanography, palaeoclimate and biotic evolution of southwest Australia. The student will reconstruct changes during the Cretaceous with a specific focus on OAE2 using sedimentary organic geochemistry GDGTs, including the TEX86 sea surface temperature proxy. Data from southern high latitudes is currently lacking (Jenkyns et al. 2012), so this project will test the extent of OAE2 high latitude warming and look for evidence of short term changes, such as the "Plenus cold event" that occurs within OAE2 in the northern hemisphere (Zheng et al. 2013). Local changes in productivity will be reconstructed using dinoflagellate cyst assemblages, to investigate oceanic upwelling and terrigenous nutrient delivery over OAE2 and the longer term Cretaceous. The project will also assess regional vegetation changes linked to the hydrological cycle by generating pollen grain and spore records over the late Cretaceous, and in high resolution over OAE2. Pristine new sediment cores recently collected during IODP Expedition 369 offshore SW Australia (Hobbs et al. 2016) are ideal for organic geochemical and palynological analyses as they are thermally immature and have a low burial depth.