Timing of the Early Triassic carbon cycle perturbations inferred from new U-Pb ages and ammonoid biochronozones
Timing of the Early Triassic carbon cycle perturbations inferred from new U-Pb ages and ammonoid biochronozones
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DOI：
10.1016/j.epsl.2007.04.023
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发表时间：
2007-06-30
影响因子：
5.3
通讯作者：
Guodun, Kuang
中科院分区：
文献类型：
--
作者：
Galfetti, Thomas;Bucher, Hugo;Guodun, Kuang
通过对单颗、热退火和化学磨蚀锆石的分析，建立了早三叠世(桂西北，中国南部)史密斯期早三叠世“致密喀什米尔岩”火山灰层中火山灰层的高精度U-Pb年龄为251.22 Ma/-0.2 Ma。这一新的日期，连同重新计算的同一剖面以前的U-Pb年龄的不确定性[M.Ovtcharova，H.Bucher，U.Schaltegger，T.Galfetti，A.Brayard，J.Guex]。中国南部早中三叠世新的U-Pb年龄：氨类生物年代带的标定及其对三叠纪生物恢复时间的意义地球星球。SCI。让我们来吧。243(2006)463-475。]可以限制早三叠世的时间框架，并导致估计的持续时间(I)对于史密斯期约为0.7+/-0.6my，(Ii)对于Griesbachian-Dienerian时间段的最大持续时间约为1.4+/-0.4my。新的U-Pb年龄大大缩小了二叠系-三叠系界线与斯帕西期(早三叠世晚期)之间的绝对年龄差距，新的年龄格架为标定早三叠世罗楼组新的碳酸盐碳同位素和氨化物记录提供了基础，这对全球对比和碳循环模拟具有重要意义。这一定标表明，早三叠世碳同位素最显著和最快的扰动发生在最早的史密斯期和早斯巴斯期之间，因此跨度约为1My。无论是什么原因导致了这些强度高、持续时间短的碳循环变化，有证据表明，这些波动、菊石和牙形刺的脉动恢复以及气候变化之间存在联系。(C)2007 Elsevier B.V.保留所有权利。
Based on analyses of single, thermally annealed and chemically abraded zircons, a new high-precision U-Pb age of 251.22 +/- 0.20 Ma is established for a volcanic ash layer within the "Kashmirites densistriatus beds" of early Smithian age (Early Triassic) from the Luolou Formation (northwestern Guangxi, South China). This new date, together with recalculated uncertainties of previous U-Pb ages from the same section [M. Ovtcharova, H. Bucher, U. Schaltegger, T. Galfetti, A. Brayard, J. Guex. New Early to Middle Triassic U-Pb ages from South China: calibration with ammonoid biochronozones and implications for the timing of the Triassic biotic recovery. Earth Planet. Sci. Lett. 243 (2006) 463-475.] allows constraining the time framework of the Early Triassic and leads to an estimated duration of (i) ca. 0.7 +/- 0.6 My for the Smithian and (ii) a maximal duration of ca. 1.4 +/- 0.4 My for the Griesbachian-Dienerian time interval. The new U-Pb age considerably reduces the absolute age gap comprised between the Permian-Triassic boundary and the Spathian (late Early Triassic).The new age framework provides the basis for the calibration of a new carbonate carbon isotope and ammonoid records of the Early Triassic Luolou Fm., which in turn are of high significance for global correlations and for carbon cycle modeling. This calibration indicates that the most significant and fastest Early Triassic carbon isotope perturbations occur between the earliest Smithian and the early Spathian, thus spanning a time interval of about 1 My. Whatever caused these carbon cycle shifts of high intensity and short duration, there is evidence for connections between these fluctuations, the pulsate recovery of ammonoids and conodonts as well as climate changes. (C) 2007 Elsevier B.V. All rights reserved.