Comparing land-based and deep-sea rock and fossil records of microplankton to test for bias in diversity patterns through time

比较陆地和深海岩石和微型浮游生物的化石记录，以测试随时间变化的多样性模式的偏差

• 批准号: NE/F016905/1
• 负责人: Andrew Smith
• 金额: $ 27.27万
• 依托单位: Natural History Museum
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF016905%2F1
• 关键词: Comparing; land; based; deep; sea

Recent reviews of how much marine sedimentary rock remains preserved on land have highlighted just how variable that record is from different time periods, both in terms of environmental representation and absolute rock volume. As a result we now know that the rock record over the continental shelf is very cyclical in structure. At its most fundamental level the Phanerozoic rock record comprises two cycles defined primarily by changes in the ratio of marine to terrestrial rock. These cycles are evident across both Northern and Southern hemispheres although their precise timing differs slightly. They arise in response to major global tectonic cycles of plate assembly and rifting. Superimposed on these are shorter-term (ca. 50 My) cycles, which are largely independent in timing from continent to continent and which reflect regional tectonic events and local sea level changes. Marine biodiversity, as measured by counts of macrofossils, also shows a cyclical pattern. These cycles match changes in the extent of continental flooding and thus could be generated through one of two processes: they could arise because of sampling bias, as the amount of marine sedimentary rock of a particular age that is ultimately preserved varies as seas expand and contract over the continents; or biological diversity could be rising and falling in tandem with the expansion and contraction of shallow marine seaways. At present it is not clear which is the predominant driver of the marine fossil record because there is high spatial heterogeneity of faunas within shallow water environments leading to a very strong species-area effect (the wider an area sampled the more species will be found). So far all the attention has been focussed on the rock and fossil records of the continental shelves. Large scale analyses of the nature of the deep-sea record and whether it correlates with marine diversity have never been explored. There are strong grounds for thinking that the deep-sea rock and fossil records might be different from that preserved on the continental shelves. For one thing much of the sedimentary record comprises near continuous biogenic deposits derived from planktonic microorganims which only rarely encroaches far onto the continental shelves. Furthermore, in the open oceans marine plankton are widely dispersed, so that any species-area effect is much less evident. Yet we also know there are hiatuses and barren intervals in the deep sea due to non-preservation, and the numbers of cores yielding fossiliferous rocks of a specific age is unlikely to be uniform over time. What is more, planktonic foraminiferans are reported to show a 30 myr cyclical rise and fall in diversity. To clarify whether fossil diversity patterns are causally linked to rock sampling patterns we will focus on the fossil record of two important planktonic groups, coccolithophorids and planktonic foraminifera. We will first identify any possible biases in the deep-sea record by assessing the distribution of gaps and non-preservation hiatuses in the sampled record of the central Atlantic, and test how much these actually affect diversity counts (for geographically widespread taxa variation in density of sampling should have a minimal effect). By recording their diversity through time from deep-sea cores and comparing this with their diversity patterns as derived from land-based outcrops, we hope to be able to show whether the 30-Myr cyclicity is a genuine biological signal or an outcome of the extent to which open oceanic sedimentation encroaches onto the continental blocks during high sea-level stands. We will also compare the nature of the deep-sea sedimentary rock and fossil records with rock and fossil records derived from land-based sections on adjacent continents to find out whether the deep-sea fossil record is immune from many of the biases affecting the shallow water record, or whether both covary in quality.

最近关于土地上保留了多少海洋沉积岩的评论，强调了该记录在不同时间段的变化，无论是在环境代表和绝对岩石量方面。结果，我们现在知道大陆架上的岩石记录在结构上非常周期性。在最基本的水平上，Phanerokoic Rock Record包括两个周期，主要由海洋与陆地岩的比例变化所定义。这些周期在北半球和南半球都很明显，尽管它们的精确时机略有不同。它们是响应板组件和裂谷的主要全球构造循环而产生的。叠加在这些较短的时间（约50 my）周期上，它们在从大陆到大陆的时机上基本独立，反映了区域构造事件和当地的海平面变化。通过大化石计数测量的海洋生物多样性也显示出周期性的模式。这些周期与大陆洪水的变化相匹配，因此可以通过两个过程之一产生：由于采样偏见，它们可能出现，因为特定年龄的海洋沉积岩石量最终被保留，随着海洋在大陆上的扩张和收缩，这些年龄最终保留下来的变化；否则生物多样性可能与浅海海道的扩张和收缩同时崛起。目前尚不清楚哪个是海洋化石记录的主要驱动力，因为在浅水环境中，动物群的空间异质性很高，导致物种区域效应非常强（越宽的区域采样了更多的物种）。到目前为止，所有的关注都集中在大陆货架的岩石和化石记录上。对深海记录的性质及其是否与海洋多样性相关的大规模分析从未探索过。有强烈的理由认为，深海岩石和化石记录可能与保存在大陆架上的唱片不同。对于一件事而言，许多沉积记录包括源自浮游生物的连续生物沉积物附近，这些沉积物源自浮游生物，这些沉积物很少在大陆架子上侵蚀。此外，在开阔的海洋浮游生物中，海洋浮游生物被广泛分散，因此任何物种面积的效应都没有那么明显。然而，我们也知道由于不保护，深海有裂口和贫瘠的间隔，并且在特定年龄的化石岩石中产生的岩心数量不太可能随着时间的流逝而均匀。此外，据报道，浮游有孔虫显示出30个MYR周期性上升和多样性下降。为了阐明化石多样性模式是否与岩石采样模式有因果关系，我们将重点介绍两个重要的浮游生物组的化石记录，即coccolithophorids和浮游生物有孔虫。我们将首先通过评估中央大西洋采样记录中的差距和非预防息液的分布来确定深海记录中的任何可能偏差，并测试这些实际上影响多样性计数的程度（对于采样密度的地理广泛分类量变化，采样的密度变化应具有最小的影响）。通过从深海核心中记录其多样性，并将其与陆基露头衍生得出的多样性模式进行比较，我们希望能够证明30myr循环性是真正的生物学信号还是开放海洋沉积物在高海平面上侵蚀大陆块的程度的结果。我们还将将深海沉积岩和化石记录的性质与邻近大陆上的陆基截面得出的岩石和化石记录进行比较，以找出深海化石记录是否免受影响浅水记录的许多偏见，还是两者之间的质量质量。

项目成果

Comparative quality and fidelity of deep-sea and land-based nannofossil records

深海和陆地超微化石记录的质量和保真度比较

• DOI: 10.1130/g32561.1
• 发表时间: 2012
• 期刊: Geology
• 影响因子: 5.8
• 作者: Lloyd G