Late Devonian events in open ocean environments: examples from Mongolia

泥盆纪晚期海洋缺氧与灭绝事件被认为是普遍存在的，海洋缺氧已被公认为这些海洋大灭绝的“驱动力”。然而，关于泥盆纪缺氧与灭绝之间的因果关系仍存在争议，因为北美东部和欧洲的表海和构造盆地普遍表现出两者之间的密切联系，而其他地区则没有。因此，我们目前的知识，例如F/F事件和Hangenberg危机，受到明显的抽样偏差的限制，因为大多数先前的研究取样赤道陆表海道或被动大陆架，主要来自欧洲和北美的地方。因此，仍有必要研究多种不同表现形式的事件，以充分理解全球海洋缺氧和灭绝的机制，并确定触发机制。中亚造山带（CAOB）是泥盆纪晚期物种灭绝和生态系统从灭绝中恢复的一个尚未得到充分研究的部分。这就是为什么我们去了蒙古，在那里我们研究了不同地体（Baruunhuurai地体和Mandalovoo - /Gurvansayhan地体）的新现场（开阔的海洋），这些事件不一定与黑色页岩和/或沥青深色石灰岩相有关。作为解决古地理样本偏差、生物地层学、F/F事件和Hangenberg危机后生物多样性变化等问题的一步，我们可以在CAOB内提供从浅层潮下到外斜坡环境和开放海洋环境的新结果，这对理解全球气候变化和强烈火山活动时期孤立生态系统的生物多样性模式有重要贡献。这可能导致了全球气候和生物圈的重大变化。但是，由于牙形石动物群稀少，以及火山碎屑喷发频繁且体积大的高物理压力环境，我们不得不处理一些限制，这两者都阻碍了对所提出的等效事件层周围的详细地层记录。因此，计划在蒙古南部的Shine-Jinst地区研究新的剖面，这些剖面最有可能属于Mandalovoo-Terrane，因此与巴彦khohuu遗址剖面相当，但很可能含有更好的牙形刺动物群。在全球气候变化期间，估计的海表温度（SST）是否与其他地方公布的数据有很大差异，例如欧洲和北美各地的表海道和/或大陆架沉积物？牙形刺将用于在事件层周围进行碳和氧同位素测定（也来自早期的野外活动），以解决这方面的问题，并将结果与已发表的数据进行比较。

Late Devonian oceanic anoxia with extinction events have been considered ubiquitous, and ocean anoxia has been the accepted “driving force” for these marine mass extinctions. However, there is still debate about the cause/effect relationship between anoxia and extinction in the Devonian, as the epeiric seas and tectonic basins of eastern North America and Europe generally show a close association between the two, but sites elsewhere do not. Thus, our current knowledge for instance of the F/F Event and Hangenberg Crisis is limited by significant sampling bias, as most previous studies sampled equatorial epicontinental seaways or passive continental shelves, primarily from localities across Europe and North America. Thus, there is still the need to study events in many differing expressions to fully comprehend the mechanisms of global ocean anoxia and extinction, and determine the trigger mechanism(s). The Central Asian Orogenic Belt (CAOB) is a yet grossly understudied part of the story of the Late Devonian extinctions and ecosystem rebound from extinctions. That was the reason, we went to Mongolia where we studied new field sites (open ocean), in different terranes (Baruunhuurai Terrane and on the Mandalovoo– /Gurvansayhan Terrane) were these events are not necessarily associated with black shales and/or bituminous dark limestone facies. As a step towards addressing problems of palaeogeographic sample bias, biostratigraphy, biodiversity changes in the aftermath of the F/F events and the Hangenberg Crisis we could present new results from shallow-subtidal to outer ramp settings and open ocean settings within the CAOB which are important contributions to understand biodiversity patterns in isolated ecosystems during a time of global climate changes and intensive volcanic activity, which may have led to significant changes in the global climate and biosphere. But we had to deal with some limitations due to scarce conodont fauna and high physical stress environment with frequent and often voluminous pyroclastic eruptions, both hampered detailed stratigraphic records around proposed equivalents of event layers. Thus, it is planned to study new sections in the Shine-Jinst area in southern Mongolia which belong most probably to the Mandalovoo-Terrane and are therefore comparable with the Bayankhohuu Ruins section, but much likely containing better conodont-fauna. Do the estimated sea surface temperatures (SST) during a time of global climate change considerably differ from areas published elsewhere, such as in epeiric seaways and/or continental shelf deposits in site across Europe and North America? Conodonts will be used to perform carbon and oxygen isotopes around the event layers (also from earlier field campaigns) to address this aspect and compare the results with published data.