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Sea-level change and carbon cycle perturbation in the Mesozoic 'greenhouse'

中生代“温室”中的海平面变化和碳循环扰动

基本信息

批准号：
NE/F011067/1
负责人：
Stephen Hesselbo
金额：
$ 3.76万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF011067%2F1
关键词：
Sea level change carbon cycle

项目摘要

An enduring and contentious issue in Mesozoic Earth history (~250 to 65 million years ago) is the importance of high-rate global sea-level changes and their potential driving mechanisms. Although a huge effort in the 1990's was put into defining sedimentary packages generated by cyclic sea-level changes, attempts to determine global extent, and by implication global mechanisms, have largely been frustrated. The principal difficulty is that the sedimentary strata that are most sensitive to sea-level change, those deposited in coastal environments, are also the most difficult to assign relative ages to on a global scale with sufficient precision. One possible means of achieve this goal is to use the ratios of stable carbon-isotopes preserved in contemporaneous plant matter. Although the carbon-isotope ratios in land plants are affected by a number of factors, the predominant factor appears to be the isotopic composition of carbon-dioxide in the atmosphere in which the plants grew. The present proposal makes use of advances in high-resolution carbon-isotope stratigraphy of the Early Jurassic in order to test correlations between a succession from a restricted seaway of the Polish Basin and open marine successions from other NW European basins that are well-characterized in terms of isotopic compositions, time-diagnostic fossils, and inferred sea-level change. In particular, the latest Pliensbachian to Early Toarcian interval of the Early Jurassic is targeted, because this time was characterized by large, potentially global, carbon-isotope fluctuations, culminating around the so-called Early Toarcian Oceanic Anoxic Event, and corresponding to major fluctuations in palaeotemperature inferred from various lines of evidence. Therefore this is amongst the most likely of Mesozoic intervals to exhibit sea-level changes driven by glacioeustasy (i.e. ice sheet expansion and contraction), if such a mechanism was indeed operating.

中生代地球历史（约2.5亿至6500万年前）中一个持久而有争议的问题是全球海平面高速变化及其潜在驱动机制的重要性。虽然在20世纪90年代，人们付出了巨大的努力来定义周期性海平面变化所产生的沉积包，但确定全球范围的尝试，以及由此产生的全球机制，在很大程度上受到了挫折。主要的困难是，对海平面变化最敏感的沉积地层，即那些沉积在沿海环境中的地层，也是最难在全球范围内以足够的精度确定相对年龄的地层。实现这一目标的一种可能的方法是利用保存在同期植物物质中的稳定碳同位素的比率。虽然陆地植物的碳同位素比率受许多因素影响，但主要因素似乎是植物生长的大气中二氧化碳的同位素组成。本提案利用早侏罗世的高分辨率碳同位素地层学的进展，以测试从波兰盆地的限制性海道继承和开放的海洋继承从其他西北欧盆地的特点是同位素组成，时间诊断化石，推断海平面变化之间的相关性。特别是，最新的Pliensbachian到早侏罗世的早Toarcian间隔是有针对性的，因为这段时间的特点是大的，潜在的全球性的，碳同位素波动，在所谓的早Toarcian海洋事件前后达到高潮，并对应于从各种证据推断的古温度的主要波动。因此，这是中生代最有可能表现出由冰川作用（即冰盖扩张和收缩）驱动的海平面变化的时期之一，如果这种机制确实在起作用的话。