Collaborative Research: Calibration of the LateTriassic-Early Jurassic Timescale Using U-Pb Dating of the High-Resolution Magnetostratigraphy of the Newark Supergroup

合作研究：利用纽瓦克超群高分辨率磁力地层U-Pb测年校准晚三叠世-早侏罗世时间尺度

• 批准号: 0447150
• 负责人: Emma Rasbury
• 金额: --
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-15 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0447150&HistoricalAwards=false
• 关键词: Collaborative; Research; Calibration; LateTriassic; Early

This grant will date sedimentary and igneous rocks from within the Newark Supergroup in an attempt to both refine the Late Triassic and Early Jurassic timescale and to test the well-grounded hypothesis that the cycles observed in the supergroup are controlled by Milankovitch orbital forcing. This grant will provide a very important test of Uranium-Lead dating in carbonates, clarify the timing of terrestrial vs. marine extinctions at the Triassic/Jurassic boundary, and provide much more precise data on the actual dates and progression of the boundary.The Newark Supergroup records the Triassic-Jurassic extinction and has been intensively studied in terms of bio-, cyclo-, and magentostratigraphy. Although the cyclostatigraphic record is often cited as recording orbital forcing, absolute age constraints on this high-resolution record are lacking. The only horizon that has been dated in this sequence is a series of basaltic flows and intrusions that were dated at 201 +/- 1 Ma. New work at MIT suggests it will be possible to date zircons from granophyric layers in basalts to a precision of 0.2 Ma or better. These basalts bracket units containing sedimentary carbonates that appear to have great potential for U-Pb dating. Comparison of the ages will test the potential for U-Pb dating of sedimentary materials for yielding accurate ages.Testing the potential of U-Pb dating of carbonates is a key area for understanding the distribution of time in thick sequences of rocks that do not contain volcanic ashes. Geochronological data are needed to address fundamental questions about Earth processes, many of which involve questions about rates or correlations. Although magnetostratigraphy and cyclostratigraphy can be used to subdivide time in the rock record, assumptions about the detailed distribution of time are impossible without precise calibration. Although the precision of U-Pb ages of carbonates appears to be limited by geologic complexity (e.g., slight initial heterogeneity in the Pb isotopes; mobility of U and daughters during early diagenesis) the accuracy may well be equal to the stated uncertainty in the age. If so, the possibility of dating carbonates to 1% (2-sigma) uncertainty will provide a much-needed geochronometer for sequences throughout the Phanerozoic for which no air-fall ashes can be identified. Graduate students at SUNY Stony Brook, MIT and Columbia University will be involved in this research. Due to the proximity of our institutions to each other as well as to some of the best studied parts of the Newark sequence we anticipate a very dynamic collaboration that will provide students with vast opportunities to use facilities at all three institutions and to enjoy a rich field experience.

这笔赠款将与纽瓦克超级团体内部的沉积和火成岩约会，以尝试改善晚期三叠纪和早期侏罗纪时间尺度，并测试良好的假设，即在超级组中观察到的周期受到Milankovitch Orbital强迫的控制。 This grant will provide a very important test of Uranium-Lead dating in carbonates, clarify the timing of terrestrial vs. marine extinctions at the Triassic/Jurassic boundary, and provide much more precise data on the actual dates and progression of the boundary.The Newark Supergroup records the Triassic-Jurassic extinction and has been intensively studied in terms of bio-, cyclo-, and magentostratigraphy.尽管经常将循环记录作为记录轨道强迫，但缺乏这种高分辨率记录的绝对年龄限制。该序列中唯一的日期的视野是一系列玄武岩流和入侵，其日期为201 +/- 1 mA。麻省理工学院的新作品表明，可以将玄武岩中颗粒层的锆石与0.2 mA或更高的精度约为。这些玄武岩支架装有含有沉积碳酸盐的单元，这些碳酸盐似乎具有巨大的U-PB约会潜力。年龄的比较将测试沉积材料的U-PB约会的潜力，以产生准确的年龄。测试碳酸盐的U-PB年代的潜力是了解不含火山灰的厚岩石序列的时间分布的关键区域。需要测量数据来解决有关地球过程的基本问题，其中许多涉及有关费率或相关性的问题。尽管可以使用磁层学和环地层学来细分岩石记录中的时间，但是如果没有精确的校准，就无法进行详细时间分布的假设。尽管碳酸盐的U-PB年龄的精度似乎受地质复杂性的限制（例如，PB同位素的初始异质性略有初始异质性；在早期成岩作用期间，U和女儿的迁移率）的准确性很可能等于年龄段的不确定性。如果是这样，将碳酸盐约会至1％（2- sigma）的不确定性的可能性将为整个Phanerozoic提供急需的地球体学计，无法鉴定出无法识别出空气失落的灰烬。 SUNY Stony Brook，麻省理工学院和哥伦比亚大学的研究生将参与这项研究。由于我们机构彼此之间的距离以及纽瓦克序列的一些最佳研究部分，我们预计将有一个非常充满活力的合作，这将为学生提供大量机会在所有三个机构中使用设施并享受丰富的实地经验。