Kasbohm Jennifer, Schoene Blair
Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
Sci Adv. 2018 Sep 19;4(9):eaat8223. doi: 10.1126/sciadv.aat8223. eCollection 2018 Sep.
Flood basalts, the largest volcanic events in Earth history, are thought to drive global environmental change because they can emit large volumes of CO and SO over short geologic time scales. Eruption of the Columbia River Basalt Group (CRBG) has been linked to elevated atmospheric CO and global warming during the mid-Miocene climate optimum (MMCO) ~16 million years (Ma) ago. However, a causative relationship between volcanism and warming remains speculative, as the timing and tempo of CRBG eruptions is not well known. We use U-Pb geochronology on zircon-bearing volcanic ash beds intercalated within the basalt stratigraphy to build a high-resolution CRBG eruption record. Our data set shows that more than 95% of the CRBG erupted between 16.7 and 15.9 Ma, twice as fast as previous estimates. By suggesting a recalibration of the geomagnetic polarity time scale, these data indicate that the onset of flood volcanism is nearly contemporaneous with that of the MMCO.
洪流玄武岩是地球历史上规模最大的火山活动，被认为会推动全球环境变化，因为它们能够在较短的地质时间尺度内释放大量的一氧化碳和二氧化硫。哥伦比亚河玄武岩群（CRBG）的喷发与约1600万年前（Ma）中新世气候适宜期（MMCO）期间大气中一氧化碳含量升高和全球变暖有关。然而，火山活动与气候变暖之间的因果关系仍具有推测性，因为CRBG喷发的时间和节奏并不为人所知。我们利用玄武岩地层中夹层含锆火山灰层的铀铅年代学方法，建立了一个高分辨率的CRBG喷发记录。我们的数据集显示，超过95%的CRBG在1670万年至1590万年前喷发，速度是之前估计的两倍。通过建议重新校准地磁极性时间尺度，这些数据表明洪流火山作用的开始与MMCO几乎同时发生。
