ID-TIMS U-Pb ZIRCON RADIOMETRIC AGES FOR THE PENNSYLVANIAN-CISURALIAN TIME SCALE: IMPLICATIONS FOR GLOBAL CORRELATION AND RATES OF PROCESSES

Schmitz 0418703晚宾夕法尼亚世到早二叠世是地球历史上的一个重要时期。这一时期的重大事件包括盘古大陆的最终组装和早期演化、海平面的重大海平面变化以及全球气候从宾夕法尼亚世的“冰屋”到二叠纪的“温室”的变化。不幸的是，在这段时间内，地质时间尺度的时间分辨率很差，这大大限制了我们澄清和关联晚古生代地质历史许多方面的能力。通常引用的时间尺度在宾夕法尼亚-二叠纪边界的估计年龄上相差多达14 Ma，并且在推断的各个阶段的持续时间上相差500%。这部分时间尺度的显著不确定性是因为分配给时期和阶段边界的数字年龄是基于相对稀疏的控制点之间的线性插值。此外，现有的控制点从地理上不同的地层剖面，分配位置的时间尺度使用几个不同的类群，并通过几种不同的放射性测量技术。由于许多基础研究直接依赖于地质年代尺度的准确性和精确性，因此改进其年龄校准至关重要，需要一个强大的，约束良好的，这是一个三层结构的、统一的晚石炭世-早二叠世生物地层学和年代学框架。一年的多学科研究工作，以校准这一时间尺度的间隔使用的典型部分和主要参考部分在南部俄罗斯-哈萨克斯坦的乌拉尔前陆。南乌拉尔山脉的三个方面使这里成为一个极好的年龄校准实验室：首先，国际上公认的早二叠世年代地层尺度的定义（西苏拉）来自这个地区，它是晚宾夕法尼亚时代的主要参考区;第二，晚古生代海洋动物群（包括小有孔虫、梭形虫、牙形刺和菊石）数量众多，保存完好，可进行精确的生物地层控制;第三，层间火山灰很常见，使得可以实现精确的放射性年龄控制。拟议的研究将具有真正的全球意义。全世界研究晚古生代广泛问题的研究人员将直接受益于这些结果。

Schmitz0418703The Late Pennsylvanian through Early Permian was an important interval in Earth's history.Significant events of this age include the final assembly and early evolution of Pangea, major eustaticchanges in sea level, and global climate change from the Pennsylvanian 'ice house' to the Permian 'hothouse.' Unfortunately, the poor temporal resolution of the geologic time scale during this intervalsubstantially limits our ability to clarify and correlate many aspects of late Paleozoic geologic history.Commonly cited time scales differ by as much as 14 Ma in the estimated age of the Pennsylvanian-Permian boundary, and vary by 500% in the inferred duration of various stages. Significant uncertaintiesin this part of the time scale arise because numerical ages assigned to period and stage boundaries arebased on linear interpolation between relatively sparse control points. Moreover, the existing controlpoints were obtained from geographically disparate stratigraphic sections, assigned positions in the timescale using several different taxa, and dated by several different radiometric techniques. Because muchfundamental research depends directly on the accuracy and precision of the geologic time scale,improving its age calibration is critical, and requires a robust, well-constrained, and internally-consistentframework of biostratigraphic and geochronologic data for the Late Carboniferous to Early Permian.This is a three-year multidisciplinary research effort to calibrate this interval of the time scaleusing the type sections and principal reference sections in the southern Ural foreland of Russia-Kazakhstan. Three aspects of the southern Urals make this an excellent laboratory for age calibration:first, the internationally accepted definition of the chronostratigraphic scale for Early Permian(Cisuralian) comes from this region, and it is a principal reference area for the Late Pennsylvanian aswell; second, late-Paleozoic marine fauna (including small foraminifera, fusulinids, conodonts, andammonoids) are numerous and well preserved, allowing precise biostratigraphic control; and third,interstratified volcanic ashes are common, making precise radiometric age control achievable. The proposed study will have truly global significance. Researchers worldwide working on a broadrange of Late Paleozoic problems will benefit directly and measurably from the results.