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

摘要：晚三叠世地磁极性时间尺度（GPTS）是从纽瓦克盆地厚厚的连续大陆记录中发展而来的，其基础是以湖相 Passaic、Lockatong 和上 Stockton 地层为代表的 2600 万年的旋回地层学，但根据河流下 Stockton 地层的沉积速率进行外推，而来自岩心孔的单一磁地层记录尚未得到验证。纽瓦克序列中三叠纪-侏罗纪边界的关联似乎是可靠的，但诺里安-雷蒂安边界的位置，特别是主要基于孢粉学的卡尼安-诺里安边界的位置，在试图合并海洋生物地层和非海洋岩石地层记录时变得非常成问题。最近提出的海洋剖面中的卡尼期-诺里安边界与纽瓦克层序的相关性将该边界置于斯托克顿组的中部，这意味着边界年龄约为 228 Ma。这比通常在地质时间尺度中显示的要早得多，尽管可用的辐射年龄数据并不排除这一点。如果得到证实，它将对我们对区域和全球历史地质学的理解产生重大影响，包括恐龙等主要陆地脊椎动物群体的进化时间和盘古大陆的裂谷。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序列的可靠性，这需要针对下斯托克顿组所代表的时间进行验证和细化。我们提出了一种双管齐下的方法来解决海相卡尼期和较早地层与纽瓦克参考剖面之间相关性的模糊性：1）对露头斯托克顿组的古地磁分析和测量，以测试和扩展普林斯顿岩心孔中描绘的极性序列，并将此记录直接与天文校准的 GPTS 联系起来，2) 对 Timesgadiouine 组（摩洛哥阿加纳盆地）相关露头地层进行古地磁分析和测量，以进行旋回地层控制。这个为期 2 年的项目的成功完成将使天文校准的 GPTS 涵盖超过 3000 万年的晚三叠世，并可能进入中三叠世。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盘古大陆分裂之前一段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落，并纳入一些可用于年龄控制但来自非海洋部分的辐射日期。我们的工作包括与摩洛哥地质学家和重要实物的合作摩洛哥国家石油公司 ONAREP 的后勤贡献除了成为该项目本身的组成部分之外，还将帮助在这一困难时期在阿拉伯和美国机构之间架起桥梁。最后，我们将开发一个包含阿拉伯语版本的网站，以便它可以用作美国和摩洛哥团体的教育工具，并围绕以下概念：这两个地区（美国东部和摩洛哥）是姐妹地质和生物省份，现在隔海相望，但曾经是同一片广阔陆地的一部分，并且彼此直接相邻。美国本科生将参与该项目的几个阶段，他们将在定量方法方面获得宝贵的经验，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.