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然和短暂的海洋缺氧事件（OAE），其特征是严重的全球变暖，可能是由火山释放的二氧化碳引发的。尽管它们对于理解地球-海洋-大气系统非常重要，但OAE的环境影响和因果机制尚未完全解决，在记录极其有限的南半球，人们对OAE的了解尤其不足。其中最大的事件之一是Cenomanian-Turonian边界的OAE 2（约94 Ma），与火山活动，突然变暖，水文循环增加，海洋营养供应，高生产力和海洋生物群的大规模灭绝有关。该项目旨在利用国际海洋发现计划（IODP）第369次考察期间获得的新岩心资料，首次重建澳大利亚西南部白垩纪前、中、后的古海洋学和植被，探讨全球气候变化对澳大利亚西南部白垩纪古海洋学、古气候和生物演化的短期和长期影响。学生将重建白垩纪期间的变化，特别关注OAE 2使用沉积有机地球化学GDGT，包括TEX 86海表温度代理。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OAE 2高纬度变暖的程度，并寻找短期变化的证据，例如北方OAE 2内发生的“Plenus冷事件”（Zheng et al. 2013）。当地生产力的变化将重建甲藻孢囊组合，调查海洋上升流和陆源营养物质输送超过OAE 2和更长期的白垩纪。该项目还将通过生成白垩纪晚期的花粉粒和孢子记录，并在OAE 2上以高分辨率评估与水文循环有关的区域植被变化。最近在IODP Expedition 369澳大利亚西南部近海（Hobbs等人，2016年）收集的原始新沉积物岩心是有机地球化学和孢粉学分析的理想选择，因为它们是热未成熟的，埋藏深度较低。

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.