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The climate development of Gondwana during the Jurassic

侏罗纪时期冈瓦纳大陆的气候发展

基本信息

批准号：
283866124
负责人：
Dr. Matthias Alberti
金额：
--
依托单位：
Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/283866124?language=en
关键词：
climate development Gondwana during Jurassic

项目摘要

Older studies claim an ice-free Jurassic world with equable warm climate conditions and weak latitudinal temperature gradients. However, this view was challenged since by a series of climate reconstructions pointing to several warmer and colder intervals, some even with short polar glaciations. Many of these studies were based on stable isotope analyses of fossil shells resulting in absolute water temperature data. Nevertheless, most of the analyzed material has been collected from Laurasian localities and often it is unknown to which extent the reconstructed temperature curves depict global or only regional events (possibly even changes in water depth at the sample localities). Climate conditions of other regions, such as the southern supercontinent Gondwana, are much less known. Furthermore, most of the available reconstructions are based on stable isotope analyses of belemnites, as these are often common in the sedimentary successions and large amounts of sample material can be extracted from their massive rostra. Research during the last few years, however, has shown that the use of belemnites often leads to an underestimation of temperatures with results being lower than those from shells of the benthic fauna. The proposed project aims to reconstruct the Jurassic climate development for a series of localities of Gondwana. Fossil material has been or will be collected from Tunisia, Egypt, Jordan, India, Madagascar, Chile, and Argentina. In many cases, the project will result in the first absolute temperature data available for these localities. Furthermore, the project will rely mainly on oysters and impunctate rhynchonellid brachiopods, thereby gaining a more reliable picture of local temperature conditions compared to results from belemnites. Water temperatures will be calculated based on stable isotope, clumped isotope, and trace element analysis. High-resolution stable isotope and trace element analyses of bivalve shells will enable an estimation of the degree of seasonality at the different localities as well as the reconstruction of other environmental parameters (e.g., the presence of upwelling currents). Combining the results, latitudinal temperature gradients will be calculated for Gondwana at different time intervals in the Jurassic. Possibly the most interesting application of the dataset assembled in the proposed project lies in a comparison with latitudinal gradients of marine invertebrate diversity. This would allow to identify whether temperatures were a major controlling factor of marine faunal patterns. As the Jurassic was a period with generally warmer climate conditions and elevated CO2-concentrations in the atmosphere compared to recent times, the results might benefit the current global warming debate. Therefore, a special focus is directed at Jurassic climate conditions along the equator, where elevated temperatures might have depleted the faunal diversity.

更早的研究声称，侏罗纪是一个没有冰的世界，气候条件温和，纬度温度梯度较弱。然而，这一观点受到了挑战，因为一系列的气候重建指向了几个变暖和变冷的时间间隔，其中一些甚至出现了短暂的极地冰川。其中许多研究是基于对化石贝壳的稳定同位素分析，从而得出绝对水温数据。然而，大多数分析材料都是从劳亚地区收集的，重建的温度曲线在多大程度上描绘了全球或仅有区域性事件(甚至可能是样本地点的水深变化)，往往是未知的。其他地区的气候条件，如南部超大陆冈瓦那，则鲜为人知。此外，大多数可用的重建是基于对伯利恒陨石的稳定同位素分析，因为这在沉积序列中经常是常见的，并且可以从其巨大的嘴部提取大量样品材料。然而，过去几年的研究表明，贝雷米特的使用往往导致对温度的低估，结果低于底栖动物贝壳的结果。拟议的项目旨在重建冈瓦那一系列地区的侏罗纪气候发展。已经或将从突尼斯、埃及、约旦、印度、马达加斯加、智利和阿根廷收集化石材料。在许多情况下，该项目将产生这些地区的第一个绝对温度数据。此外，该项目将主要依靠牡蛎和浸渍皱纹软体动物腕足类，从而与贝莱米特的结果相比，获得更可靠的当地温度条件的图像。水温将根据稳定同位素、块状同位素和微量元素分析来计算。对双壳类贝壳进行高分辨率稳定同位素和微量元素分析，将能够估计不同地点的季节性程度以及重建其他环境参数(例如，是否存在上升流)。结合这些结果，将计算出冈瓦那在侏罗纪不同时间段的纬度温度梯度。拟议项目中汇集的数据集最有趣的应用可能在于与海洋无脊椎动物多样性的纬度梯度进行比较。这将有助于确定温度是否是海洋动物群模式的主要控制因素。由于侏罗纪是一个气候条件普遍变暖、大气中二氧化碳浓度较高的时期，这一结果可能有利于当前的全球变暖辩论。因此，特别关注赤道一带的侏罗纪气候条件，那里的高温可能已经耗尽了动物群的多样性。