Extension of the Newark Geomagnetic Polarity Reference Sequence to Address Problems of the Carnian and the Middle Triassic

摘要纽瓦克盆地晚三叠世的地磁极性时间尺度（GPTS）是基于湖相Passaic、Lockatong和上斯托克顿组为代表的2600万年旋回地层，而下斯托克顿组则是基于沉积速率的外推，后者的单一磁地层记录尚未得到核孔的验证。纽瓦克演替中三叠纪-侏罗纪界线的对比似乎是可靠的，但在试图合并海洋生物地层学和非海洋岩石地层学记录时，主要基于粉粉学的诺里安-雷蒂安界线的位置，特别是卡尼安-诺里安界线的位置，已经变得非常有问题。最近提出的海相剖面卡尼—诺里界线与纽瓦克层序的对比表明，该界线位于斯托克顿组中部，表明界线年龄为~228 Ma。这比通常在地质时间尺度上显示的要老得多，尽管现有的放射性年龄数据没有排除这一点。如果得到证实，它将对我们对区域和全球历史地质的理解产生重大影响，包括对恐龙等陆地脊椎动物主要种群的进化时间和盘古大陆裂谷的理解。然而，海相和非海相层序的相关性在很大程度上取决于参考极性层序的可靠性，该参考极性层序需要在斯托克顿组下部所代表的时间内进行验证和完善。我们提出了一种双管齐下的方法来解决海洋卡尼期和更古老地层与纽瓦克参考剖面之间相关性的模糊性：1)对斯托克顿组露头进行古地磁分析与测量，以验证和扩展普林斯顿岩心孔圈定的极性序列，并将此记录与天文标定的GPTS直接联系起来；2)对摩洛哥阿加纳盆地Timesgadiouine组相关露头地层进行古地磁分析与测量，进行旋回地层控制。这个为期2年的项目的成功完成，将把天文校准的GPTS扩展到3000多万年的晚三叠世，甚至可能进入中三叠世。精确的地质时间尺度具有广泛的适用性，例如，它将提供一个难得的机会来解决在泛大陆分裂之前的一个重要而有趣的地质时间间隔内的海洋和非海洋相关性，在全球范围内关联重要的陆地脊椎动物动物群组合，并结合一些为数不多的可用于年龄控制但来自非海洋部分的辐射测量日期。我们的工作包括与一位摩洛哥地质学家的合作，以及摩洛哥国家石油公司ONAREP的大量实物后勤捐助，ONAREP除了是项目本身不可或缺的一部分外，还有助于在这一困难时期建立阿拉伯和美国机构之间的桥梁。最后，我们将开发一个包含阿拉伯语版本的网站，以作为美国和摩洛哥群体的教育工具，并围绕这两个地区（美国东部和摩洛哥）是姊妹的地质和生物省的概念，现在被海洋隔开，但曾经是同一块巨大陆地的一部分，彼此直接相邻。美国本科生将参与该项目的几个阶段，在此期间他们将获得定量方法方面的宝贵经验，并在美国接触阿拉伯科学家和文化。

ABSTRACTThe geomagnetic polarity time scale (GPTS) for the Late Triassic developed from the thick, continuous continental record from the Newark basin is based on cycle stratigraphy for 26 million years represented by the lacustrine Passaic, Lockatong and upper Stockton formations but on extrapolation of sedimentation rates for the fluvial lower Stockton Formation for which the single magnetostratigraphic record from a core hole has not been verified. Correlation of the Triassic-Jurassic boundary within the Newark succession seems secure but placements of the Norian-Rhaetian and especially the Carnian-Norian boundaries based largely on palynology have become highly problematical in attempts to merge the marine biostratigraphic and nonmarine lithostratigraphic records. Recently proposed correlations of the Carnian-Norian boundary in marine sections to the Newark sequence place this boundary in the middle of the Stockton Formation and would imply a boundary age of ~228 Ma. This is appreciably older than usually shown in geologic time scales although not precluded by available radiometric age data. If confirmed it would have major implications to our understanding of regional and global historical geology including the timing of evolution of major groups of land vertebrates like the dinosaurs and the rifting of Pangea. However, the correlation of the marine and nonmarine sequences depends strongly on the reliability of a reference polarity sequence, which needs to be validated and refined for the time represented by the lower Stockton Formation.We propose a two-pronged approach to resolving the ambiguities in the correlations between the marine Carnian and older strata and the Newark reference section: 1) paleomagnetic analysis and measurement of outcropping Stockton Formation to test and extend the polarity sequence delineated in the Princeton corehole and to link this record directly to the astronomically calibrated GPTS, and 2) paleomagnetic analysis and measurement of correlative outcropping strata of the Timesgadiouine Formation (Argana Basin, Morocco) for cycle stratigraphic control.Successful completion of this 2-year project will extend the astronomically calibrated GPTS to encompass more than 30 million years of the Late Triassic and possibly into the Middle Triassic. A precise geologic time scale has broad applicability and will, for example, provide a rare opportunity to resolve marine and nonmarine correlations over a significant and interesting interval of geologic time just prior to the breakup of Pangea, to correlate important land vertebrate faunal assemblages on a global scale, and to incorporate some of the few radiometric dates that are available for age control but which come from nonmarine sections.Our work includes collaboration with a Moroccan geologist and a significant in-kind logistical contribution from ONAREP, the Moroccan state oil company that in addition to being integral to the project itself will help build bridges between Arab and U.S. institutions during this difficult time. Finally, we will develop a web site that will include an Arabic version so that it can be used as an educational tool for both U.S. and Moroccan groups and revolve around the concept that the two areas (eastern U.S. and Morocco) are sister geological and biological provinces, now separated by an ocean, but were once part of the same vast land mass and directly adjacent to one another. U.S. undergraduates will be involved with several stages of this project in which they will get valuable experience in quantitative methods as well as exposure in the U.S. to Arab scientists and culture.