Three-Dimensional Morphometry of Ooids in Oolites: A New Tool for More Accurate and Precise Paleoenvironmental Interpretation
Three-Dimensional Morphometry of Ooids in Oolites: A New Tool for More Accurate and Precise Paleoenvironmental Interpretation
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DOI：
10.1029/2020jf005601
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发表时间：
2021-04-01
影响因子：
3.9
通讯作者：
Maloof, Adam
中科院分区：
文献类型：
--
作者：
Howes, Bolton;Mehra, Akshay;Maloof, Adam
在地层记录中普遍存在的鲕粒，以及它们与浅水碳酸盐环境的联系，使鲕粒成为一个重要的古环境指标。最近的进展，在理论上理解的卵状体形态，沿着从特克斯和凯科斯群岛，大盐湖，巴哈马群岛的实证研究，已经表明，卵状体的形态是指示沉积环境和水力条件。为了将现代环境中的这一知识应用于地球历史的地层记录，研究人员测量了二维表面上的石化卵的大小和形状（即，薄切片），通常假设随机的2D切片与细胞核相交并且卵圆形的取向是已知的。在这里，我们证明了这些假设很少是真的，导致主轴长度等指标的误差高达35%。我们提出了一种通过连续研磨和成像进行3D重建的方法，该方法能够准确测量单个鲕粒内的形态，以及样品的分选和孔隙度。我们还提供了三个案例研究，使用的形态学ooids中的oeclampus提取环境信息。每个案例研究表明，如果环境信号相对于2D测量的误差较大，则2D测量可能是有用的。然而，3D测量大大提高了环境解释的准确性和精确度。这项研究的重点是oeros，但从2D测量的错误并不是唯一的oeros，这种方法可以用来提取准确的颗粒和孔隙度测量从任何连贯的，颗粒状的样品。
The prevalence of ooids in the stratigraphic record, and their association with shallow-water carbonate environments, make ooids an important paleoenvironmental indicator. Recent advances in the theoretical understanding of ooid morphology, along with empirical studies from Turks and Caicos, Great Salt Lake, and The Bahamas, have demonstrated that the morphology of ooids is indicative of depositional environment and hydraulic conditions. To apply this knowledge from modern environments to the stratigraphic record of Earth's history, researchers measure the size and shape of lithified ooids on two-dimensional surfaces (i.e., thin sections), often assuming that random 2D slices intersect the nuclei and that the orientation of the ooids is known. Here, we demonstrate that these assumptions rarely are true, resulting in errors of up to 35% for metrics like major axis length. We present a method for making 3D reconstructions by serial grinding and imaging, which enables accurate measurement of the morphology of individual ooids within an oolite, as well as the sorting and porosity of a sample. We also provide three case studies that use the morphology of ooids in oolites to extract environmental information. Each case study demonstrates that 2D measurements can be useful if the environmental signal is large relative to the error from 2D measurements. However, 3D measurements substantially improve the accuracy and precision of environmental interpretations. This study focuses on oolites, but errors from 2D measurements are not unique to oolites; this method can be used to extract accurate grain and porosity measurements from any coherent, granular sample.