Automated Tools for Layer Recognition (BMPix) and Counting (PEAK)

We present tools for rapid and quantitative detection of sediment lamination. The BMPix tool extracts color and gray-scale curves from images at pixel resolution. The PEAK tool uses the gray-scale curve and performs, for the first time, fully automated counting of laminae based on three methods. The maximum count algorithm counts every bright peak of a couplet of two laminae (annual resolution) in a smoothed curve. The zero-crossing algorithm counts every positive and negative halfway-passage of the curve through a wide moving average, separating the record into bright and dark intervals (seasonal resolution). The same is true for the frequency truncation method, which uses Fourier transformation to decompose the curve into its frequency components before counting positive and negative passages.
We applied the new methods successfully to tree rings, to well-dated and already manually counted marine varves from Saanich Inlet, and to marine laminae from the Antarctic continental margin. In combination with AMS14C dating, we found convincing evidence that laminations in Weddell Sea sites represent varves, deposited continuously over several millennia during the last glacial maximum.
The new tools offer several advantages over previous methods. The counting procedures are based on a moving average generated from gray-scale curves instead of manual counting. Hence, results are highly objective and rely on reproducible mathematical criteria. Also, the PEAK tool measures the thickness of each year or season. Since all information required is displayed graphically, interactive optimization of the counting algorithms can be achieved quickly and conveniently.

本研究提出了用于快速定量检测沉积纹层（sediment lamination）的工具集。BMPix工具可从图像中以像素分辨率提取色彩与灰度曲线。PEAK工具以灰度曲线为输入，首次实现了基于三种方法的纹层全自动计数：极大值计数算法可在平滑曲线中统计每一组双纹层（年分辨率）的亮峰数量；过零算法通过宽窗口移动平均处理曲线，统计曲线穿越零点的正负过零点数量，将记录划分为亮暗区间（季节分辨率）；频率截断法则先通过傅里叶变换将曲线分解为各频率分量，再统计正负穿越次数，与过零算法逻辑一致。

本研究将该套新方法成功应用于三类对象：树轮、萨尼奇湾（Saanich Inlet）已精确测年且经人工计数的海洋纹泥（varves），以及南极大陆边缘的海洋纹层。结合加速器质谱碳-14测年（AMS14C dating），本研究获得了可靠证据：威德尔海（Weddell Sea）站位的沉积纹层实为纹泥，在末次冰盛期（last glacial maximum）期间持续沉积了数千年。

相较于传统方法，本研究提出的新工具集具备多项核心优势：计数流程基于灰度曲线生成的移动平均而非人工计数，因此结果具备高度客观性且遵循可复现的数学判定标准；PEAK工具可测量每一年或每一季的纹层厚度；此外，由于所需全部信息均以图形化方式展示，可快速便捷地完成计数算法的交互式优化。