The astronomical rhythm of Late-Devonian climate change (Kowala section, Holy Cross Mountains, Poland)
The astronomical rhythm of Late-Devonian climate change (Kowala section, Holy Cross Mountains, Poland)
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DOI：
10.1016/j.epsl.2013.01.016
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发表时间：
2013-03-01
影响因子：
5.3
通讯作者：
Claeys, Philippe
中科院分区：
文献类型：
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作者：
De Vleeschouwer, David;Rakocinski, Michal;Claeys, Philippe
石灰岩和页岩或泥灰岩之间的韵律交替是波兰圣十字山脉著名的科瓦拉段的特征。对该剖面的两个层段进行了研究，以寻找轨道旋回地层学的证据。最古老的间隔跨越弗拉斯阶-法门阶边界，沉积在中生代最热的温室气候之下。最年轻的间隔包括泥盆纪-石炭纪（D-C）边界，这是地球气候历史上的一个关键时刻，见证了从温室到冰库的转变。对于Frasnian-Famennian层序，岩性变化与405-kyr和100-kyr偏心力一致，并提出了一个循环地层浮动时标。振幅调制模式与天文学理论一致，并通过高分辨率稳定同位素记录中的岁差周期的识别，证实了所观察到的岩性节奏偏心周期的解释。由此产生的相对时间尺度表明，类似于800 kyr分离的下和上凯尔瓦瑟事件（LKE和UKE，分别），两个缺氧的时期，最终在大规模的生物多样性丧失的结束弗拉斯。Th/U和黄铁矿framboid分析表明，在UKE期间，氧水平保持在400 kyr的低水平，Δ C-13（org）测量表明，在碳循环达到稳定状态之前，经过了600 kyr以上，经过了+3/1000 UKE偏移。法门阶-图尔奈阶（D-C）间隔也揭示了偏心率和岁差相关的岩性变化。与岁差有关的变化清楚地表明了100 kyr束的分组。该层段的法门阶部分以几种独特的缺氧黑色页岩为特征，包括Annulata页岩、Dasberg页岩和Hangenberg页岩。我们的高分辨率旋回地层框架表明，这些页岩沉积在2.2和2.4百万年的时间间隔分别。这些持续时间强烈表明长周期（类似于240万年）偏心率周期和环空、达斯贝格和汉根贝格缺氧页岩的发展之间存在联系。据推测，这些黑色页岩形成海侵条件下，当极高的偏心率促进崩溃的小大陆冰盖在最南纬度的冈瓦纳西部。(C)2013爱思唯尔有限公司版权所有。
Rhythmical alternations between limestone and shales or marls characterize the famous Kowala section, Holy Cross Mountains, Poland. Two intervals of this section were studied for evidence of orbital cyclostratigraphy. The oldest interval spans the Frasnian-Famennian boundary, deposited under one of the hottest greenhouse climates of the Phanerozoic. The youngest interval encompasses the Devonian-Carboniferous (D-C) boundary, a pivotal moment in Earth's climatic history that saw a transition from greenhouse to icehouse. For the Frasnian-Famennian sequence, lithological variations are consistent with 405-kyr and 100-kyr eccentricity forcing and a cyclostratigraphic floating time-scale is presented. The interpretation of observed lithological rhythms as eccentricity cycles is confirmed by amplitude modulation patterns in agreement with astronomical theory and by the recognition of precession cycles in high-resolution stable isotope records. The resulting relative time-scale suggests that similar to 800 kyr separate the Lower and Upper Kellwasser Events (LKE and UKE, respectively), two periods of anoxia that culminated in massive biodiversity loss at the end of the Frasnian. Th/U and pyrite framboid analyses indicate that during the UKE, oxygen levels remained low for 400 kyr and delta C-13(org) measurements demonstrate that more than 600 kyr elapsed before the carbon cycle reached a steady state after a + 3 parts per thousand UKE excursion. The Famennian-Tournaisian (D-C) interval also reveals eccentricity and precession-related lithological variations. Precession-related alternations clearly demonstrate grouping into 100-kyr bundles. The Famennian part of this interval is characterized by several distinctive anoxic black shales, including the Annulata, Dasberg and Hangenberg shales. Our high-resolution cyclostratigraphic framework indicates that those shales were deposited at 2.2 and 2.4 Myr intervals respectively. These durations strongly suggest a link between the long-period (similar to 2.4 Myr) eccentricity cycle and the development of the Annulata, Dasberg and Hangenberg anoxic shales. It is assumed that these black shales form under transgressive conditions, when extremely high eccentricity promoted the collapse of small continental ice-sheets at the most austral latitudes of western Gondwana. (C) 2013 Elsevier B.V. All rights reserved.