Quantification of deep-time orbital forcing by average spectral misfit
Quantification of deep-time orbital forcing by average spectral misfit
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DOI：
10.2475/05.2007.01
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发表时间：
2007-05
影响因子：
2.9
通讯作者：
S. Meyers;B. Sageman
中科院分区：
文献类型：
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作者：
S. Meyers;B. Sageman
古代地层内米兰科维奇轨道周期性的量化已成为细化地质时间尺度的主要工具。然而，深时古气候记录中轨道信号的准确表征通常受到空间节律与时间周期校准的辐射时间限制不足的挑战。这个问题可能会给导数轨道时间尺度带来很大的误差。在这项研究中，我们开发了一种识别和校准旋回地层记录中轨道周期性的新方法。该方法（平均光谱失配，或 ASM）可对保留轨道强迫记录的地层区间的最佳沉积速率进行客观估计。该技术还提供了拒绝原假设（无轨道信号）的正式统计检验。应用该方法评估西部内陆盆地上部 Bridge Creek 石灰岩段（Turonian）的轨道循环性突出了这种新的旋回地层工具的实用性，并提供了一种独立评估岩性旋回的相互冲突的解释的方法。重要的是，ASM 提供了一个新的一致标准，可以用来比较轨道时间尺度。因此，轨道时间尺度的质量可以通过报告其平均谱失配和零假设显着性水平来正式鉴定。该技术将允许改进中生代/新生代轨道时间尺度并将轨道时间尺度发展扩展到古生代，因为该方法不依赖于严格约束的辐射年龄数据。
Quantification of Milankovitch orbital cyclicity within ancient strata has become a principal tool for refinement of the geologic time scale. However, accurate characterization of the orbital signal in deep time paleoclimate records is commonly challenged by inadequate radiometric time constraints for calibration of the spatial rhythms to temporal periods. This problem can potentially introduce large errors into derivative orbital timescales. In this study we develop a new method for the identification and calibration of orbital cyclicity in cyclostratigraphic records. The method (average spectral misfit, or ASM) yields an objective estimate of the optimal sedimentation rate for a stratigraphic interval that preserves a record of orbital forcing. The technique also provides a formal statistical test for rejecting the null hypothesis (no orbital signal). Application of the method to assess orbital cyclicity in the upper Bridge Creek Limestone Member (Turonian) of the Western Interior Basin highlights the utility of this new cyclostratigraphic tool, and provides a means to independently evaluate conflicting interpretations of the lithologic cycles. Importantly, ASM offers a new consistent standard by which orbital timescales may be compared. Hence, the quality of an orbital timescale can be formally qualified by reporting its average spectral misfit and null hypothesis significance level. This technique will permit improvement of Mesozoic/Cenozoic orbital timescales and extension of orbital time scale development into the Paleozoic, as the method is not dependent upon well-constrained radiometric age data.