Table1_Zircon of Triassic Age in the Stuttgart Formation (Schilfsandstein)—Witness of Tephra Fallout in the Central European Basin and New Constraints on the Mid-Carnian Episode.DOCX

The Carnian Stuttgart-Formation (Schilfsandstein) of the Central European Basin contains relics of Triassic volcanic detritus in form of euhedral zircon grains and authigenic analcime. Multiple LA-ICP-MS spot analyses of single zircon crystals from an outcrop near Heilbronn (SW Germany) yielded weighted average 206Pb/238U ages between 250 and 230 Ma, providing evidence for tephra fallout in the southern part of the Central European Basin related to Olenekian, Anisian–Ladinian and Carnian volcanic activity. The tephra was probably transported by monsoonal circulations from volcanic centres of the NW Tethys to the Central European Basin. The four youngest zircon crystals gave a weighted average 206Pb/238U age of 231.1 ± 1.6 Ma (10 analyses), which is interpreted to date syn-depositional tephra fallout into the fluvial Lower Schilfsandstein Member of the Stuttgart Formation. This new maximum depositional age provides the first evidence that deposition of the Stuttgart Formation, which represents the type-example of the mid-Carnian episode, a global episode of enhanced flux of siliciclastic detritus and related environmental perturbations, occurred during the Tuvalian 2 substage at ca. 231 Ma, about 3 million years later than suggested by previous correlations. Zircon grains with weighted average 206Pb/238U ages of 236.0 ± 1.2 Ma (n = 17) and 238.6 ± 1.5 Ma (n = 6) and 206Pb/238U ages between 241 ± 6 and 250 ± 3 Ma point to the presence of tephra in early Carnian to Olenekian strata of the Keuper to Buntsandstein Groups. Traces of these reworked tephra were incorporated into the Stuttgart Formation due to fluvial erosion in the southern Central European Basin and at its margins.

欧洲中部盆地卡尼阶斯图加特组（施利夫桑德斯坦）中保存有志留纪火山碎屑的遗存，以自形锆石颗粒和自生沸石的形式出现。对位于德国海因布隆（西南部）一处露头中单个锆石晶体的多次激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）点分析，得出加权平均的206Pb/238U年龄介于2.50亿至2.30亿年前，为欧洲中部盆地南部存在火山灰喷发提供了证据，这与奥伦克阶、阿尼阶-拉丁阶和卡尼阶的火山活动相关。这些火山灰很可能是由西北特提斯地区的火山中心通过季风环流输送到欧洲中部盆地的。四个最年轻的锆石晶体给出了加权平均的206Pb/238U年龄为231.1 ± 1.6百万年（分析次数为10次），这被解释为斯图加特组河流下层的沉积期火山灰喷发的时间。这一新的最大沉积年龄为斯图加特组的沉积提供了首例证据，该组代表中卡尼期的典型例子，全球硅质碎屑物质增流和环境扰动的事件，发生在图瓦利安2亚期，大约在2.31亿年前，比先前关联提出的晚约300万年。加权平均的206Pb/238U年龄为236.0 ± 1.2百万年（样本数n = 17）、238.6 ± 1.5百万年（样本数n = 6）以及介于241 ± 6至250 ± 3百万年的206Pb/238U年龄表明，在基尤珀组和布恩特桑德斯坦组的早卡尼阶至奥伦克阶地层中存在火山灰。这些重新工作的火山灰痕迹被纳入斯图加特组，这是由于欧洲中部盆地南部及其边缘的河流侵蚀作用所致。