Whither cyclostratigraphy? Testing the Gamma Method on Upper Pleistocene deep‐sea sediments, North Atlantic Deep Sea Drilling Project Site 609
Whither cyclostratigraphy? Testing the Gamma Method on Upper Pleistocene deep‐sea sediments, North Atlantic Deep Sea Drilling Project Site 609
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旋回地层学在哪里测试上更新世深海沉积物的伽马方法，北大西洋深海钻探项目 609 号站点
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发表时间：
1996
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通讯作者：
M. Kominz
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作者：
M. Kominz
1 摘要。伽马分析是一种调整循环沉积物的程序，其中伽马被定义为 1/沉积率，该分析被应用于来自北大西洋的深海钻探项目 609 站点的上更新世灰度记录。当主周期调谐到进动拍频时，伽马调谐时间序列的频谱会产生偏心率、倾斜度和进动索引信号。然而，时间尺度明显太长，这表明伽马调谐过程中使用的一些主要周期具有比进动节拍更高的频率。通过在 I 0-12 kyr 处过滤 SPECMAP 校准的时间序列，可以从调谐过程中去除杂散周期。在这种情况下，得到的伽马校正光谱看起来更像是 SPECMAP 调谐时间序列的光谱。然而，时间序列仍然有点太长。正演模型与堆芯模型的结果一致。也就是说，伽马方法在揭示轨道控制记录中的轨道周期性方面非常稳健，其中沉积速率取决于相。然而，该方法不能产生准确的时间序列。完全拒绝伽马结果的标准明确为 (1) 最小二乘结果包括负伽马值或 (2) 所得光谱不显示 或 位签名。沉降率的变化大于 ±5% 会导致时间序列不正确。然而，高达±15%的沉降率变化通常会产生很强的轨道光谱，有时，该方法还可以生成噪声高达±25%的轨道光谱。该方法在预测伽马值或沉降速率方面不那么稳健。虽然它通常区分沉积速率相对较高的相和沉积速率相对较低的相，但预测值可能不正确2倍。因此，虽然时间序列的伽玛调整比观测到的厚度有所改进，但所得的时间尺度并不正确。这些结果对旋回地层学具有重要意义。从时间序列生成的轨道谱显然是不正确的，这使人们对周期性作为约会工具产生了怀疑。
1 Abstract. Gamma analysis, a procedure for tuning cyclic sediments in which gamma is defined as 1/sedimentation rate, was applied to the upper Pleistocene gray scale record of Deep Sea Drilling Project site 609 from the North Atlantic. The spectrum of the gamma-tuned time series produces eccentricity, obliquity, and precession index signals when the primary periodicity is tuned to the precessional beat frequency. However, the timescales are significantly too long, suggesting that some of the primary cycles used in the gamma tuning procedure have higher frequency than the precessional beat. By filtering the SPECMAP-calibrated time series at I 0-12 kyr the spurious cy cles are removed from the tuning procedure. In this case, the resulting gamma-corrected spectra look much more like that of the SPECMAP-tuned time series. However, the time series remains slightly too long. Forward modeling is consistent with the results from modeling the core. That is, the gamma method is quite robust at revealing orbital periodicity in an orbitally controlled re cord for which sedimentation rates are facies dependent. However, the method does not produce an accurate time series. Criteria for complete rejection of gamma results are clarified as either (1) least squares results include negative gamma values or (2) the resulting spectrum does not show an or bital signature. Variation on sedimentation rates greater than ±5% result in incorrect time series. However, variations on sedimentation rates as high as ±15% generally reproduce strong orbital spectra, and occasionally, the method can also generate an orbital spectrum with up to ±25% noise. The method is not as robust in predicting gamma values or sedimentation rates. Although it generally distinguishes facies with relatively high sedimentation rates from facies with relatively low sedimentation rates, the values predicted may be incorrect by a factor of2. Thus while gamma tuning of the time series is an improvement over observed thicknesses, the resulting timescale is not correct. The implications of these results for cyclostratigraphy are significant. The generation of an orbital spectrum from a time series that is demonstrably incorrect casts doubt on cyclicity as a dating tool.