Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations
Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations
复制标题
DOI：
10.1016/j.epsl.2016.08.038
复制
发表时间：
2016-12
影响因子：
5.3
通讯作者：
M. Ruhl;S. Hesselbo;S. Hesselbo;L. Hinnov;H. Jenkyns;Weimu Xu;J. Riding;M. Storm;D. Minisini-
中科院分区：
文献类型：
--
作者：
M. Ruhl;S. Hesselbo;S. Hesselbo;L. Hinnov;H. Jenkyns;Weimu Xu;J. Riding;M. Storm;D. Minisini-
早侏罗世经历了多期全球气候和古海洋学的重大变化、生物更替和全球地球化学旋回的扰动，通常与大型火成岩省火山活动有关。这一时期的另一个特征是泛大陆的初始分裂，浅海相盆地和海洋门户的开放和形成，其时间限制很差。在这里，我们发现Pliensbachian阶段和Sinemurian-Pliensbachian全球碳循环扰动（以δ 13c负移2 - 4‰为标志）的持续时间分别为~ 8.7和~ 2 Myr。我们将浮动Pliensbachian时间尺度调整到405 Kyr偏心解（La2010d），并提出了一个修正的早侏罗世时间尺度，其Sinemurian期持续时间显著缩短为6.9±0.4 Myr。在新的时间尺度下，现有的Pliensbachian海水87 Sr/86 Sr记录在Pliensbachian的1 ~ 2 Myr期间显示出相对稳定的值，叠加在早侏罗世87 Sr/86 Sr的长期下降上。这个87 Sr/86 Sr的高原值与Sinemurian-Pliensbachian边界碳循环扰动一致。它可能与中大西洋岩浆省（CAMP）火山活动的晚期有关，该活动引起大陆地壳物质的全球风化增强，导致辐射成因的锶通量增加到全球海洋。
Abstract The Early Jurassic was marked by multiple periods of major global climatic and palaeoceanographic change, biotic turnover and perturbed global geochemical cycles, commonly linked to large igneous province volcanism. This epoch was also characterised by the initial break-up of the super-continent Pangaea and the opening and formation of shallow-marine basins and ocean gateways, the timing of which are poorly constrained. Here, we show that the Pliensbachian Stage and the Sinemurian–Pliensbachian global carbon-cycle perturbation (marked by a negative shift in δ 13 C of 2–4‰), have respective durations of∼ 8.7 and∼ 2 Myr. We astronomically tune the floating Pliensbachian time scale to the 405 Kyr eccentricity solution (La2010d), and propose a revised Early Jurassic time scale with a significantly shortened Sinemurian Stage duration of 6.9±0.4 Myr. When calibrated against the new time scale, the existing Pliensbachian seawater 87 Sr/86 Sr record shows relatively stable values during the first∼ 2 Myr of the Pliensbachian, superimposed on the long-term Early Jurassic decline in 87 Sr/86 Sr. This plateau in 87 Sr/86 Sr values coincides with the Sinemurian–Pliensbachian boundary carbon-cycle perturbation. It is possibly linked to a late phase of Central Atlantic Magmatic Province (CAMP) volcanism that induced enhanced global weathering of continental crustal materials, leading to an elevated radiogenic strontium flux to the global ocean.