DOI: 10.1016/j.palaeo.2014.11.001
论文题名: Astronomically forced cyclicity in the Upper Ordovician and U-Pb ages of interlayered tephra, Oslo Region, Norway
作者: Svensen H.H. ; Hammer Ø. ; Corfu F.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2015
卷: 418 起始页码: 150
结束页码: 159
语种: 英语
英文关键词: Milankovitch
; Ordovician
; Radiometric dating
; Tephras
英文摘要: The Late Ordovician world experienced a series of huge volcanic eruptions, recorded as the big Deicke, Millbrig and Kinnekulle bentonites, together with numerous thinner beds. The Kinnekulle event can be traced across northwestern Europe. U-Pb zircon ages are here presented of both the Kinnekulle K-bentonite and the uppermost recorded tephra layer in the Upper Ordovician of the Oslo Region, Norway. The tephras are located in the upper part of the Arnestad Formation (Sandbian) south of Oslo and gave ages of 454.52. ±. 0.50. Ma (the Kinnekulle K-bentonite) and 453.91. ±. 0.37. Ma (the upper Grimstorp K-bentonite). The dated tephras are separated by a 7. m thick shale succession with subordinate nodular limestone beds. Although the two U-Pb ages overlap within errors, statistical considerations indicate a most likely time interval of about 600. kyr between the tephras. High-resolution magnetic susceptibility logging in the same section shows cycles that likely represent changes in sediment supply in response to astronomical forcing. Spectral analysis shows the presence of long (400. kyr) and short (100. kyr) eccentricity bands, and obliquity components in the 30. kyr band. Precessional cycles are not detected. Based on this method, it is possible to estimate a time interval of 766. kyr between the two tephra events, and the radiometric dating therefore does not exclude a Milankovitch interpretation of the cycles. This opens new possibilities for understanding the evolution of one of the world's best preserved Ordovician marine systems. © 2014 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69051
Appears in Collections: 过去全球变化的重建
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作者单位: Physics of Geological Processes, University of Oslo, Pb. 1048, Oslo, Norway; Natural History Museum, University of Oslo, Pb. 1172, Oslo, Norway; Department of Geosciences, University of Oslo, Pb. 1047, Oslo, Norway
Recommended Citation:
Svensen H.H.,Hammer Ø.,Corfu F.. Astronomically forced cyclicity in the Upper Ordovician and U-Pb ages of interlayered tephra, Oslo Region, Norway[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2015-01-01,418