Japan. 5Frontier Research Center for Energy and Resources, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. 6Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan. Correspondence and requests for materials should be addressed to Y.K. (email: [email protected])Scientific RepoRts | 6:29603 | DOI: 10.1038/srepwww.nature.com/scientificreports/Figure 1. Locations of the sites used in this study. Circles represent Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) drilling sites, and squares indicate the University of Tokyo piston core sites. Sites filled in black are age-constrained and were thus used for reconstruction of the spatiotemporal distribution of independent components (ICs). White lines indicate tracks of each site, with tiny circles marking palaeopositions of each site in 5 Myr steps. Sites with red and blue labels indicate representative high-IC1 and high-IC4 sediments, respectively. Bathymetric data are from ETOPO2v2 (NOAA National Geophysical Data Center, 2006; https://www.ngdc.noaa. gov/mgg/global/etopo2.html). This map was created by using Generic Mapping Tools software (https://www. soest.hawaii.edu/gmt/), Version 4.5.8 59, and GPlates software30,31 (http://www.gplates.org), Version 1.2.0.Although application of traditional multivariate statistical analyses such as Principal Component Analysis (PCA) or Factor Analyses (FA) to geochemical data can be insightful, these methods have limitations for use and cannot be applied to certain datasets such as those discussed here. Both PCA and FA transform the data using only the mean and variance, or first- and second-order statistics. This implies that the extracted new variables, known as principal components or common factors, are mutually independent in the true sense only when the observed data constitute a multivariate Gaussian distribution9. In fact, the sediment data of the Pacific and Indian oceans exhibit large skewness and multimodal distributions (Supplementary Fig. S1); therefore, application of PCA or FA to extract independent features is not necessarily appropriate10,11. The aforementioned constraints notwithstanding, a number of previous works have demonstrated fruitful results by applying multivariate analyses to datasets of tens to hundreds of samples. Here, we build upon these studies of marine sediments and order PD173074 expand our perspective to examine global-scale features by using a new statistical approach on a massive geochemical dataset. We construct a hemisphere-scale compositional dataset of 3,968 bulk sediment samples from 82 sites in the Pacific Ocean and 19 sites in the Indian Ocean (Fig. 1). Moreover, we employ Independent Component Analysis (ICA) to identify the geochemical signatures hidden in the huge dataset of deep-sea sediments. ICA is a relatively new computational statistical technique established in the fields of TAPI-2 biological activity neuroscience and information science during the past quarter century9; its utility has also been recognised in the geochemical field2,11?5. ICA can extract original independent source signals from observed signals on the basis of a fundamental assumption that the observed data consist of mutually independent source signals showing non-Gaussian distributions9. As the result of ICA, the original multi-elemental data can be expressed by a combination of independent c.Japan. 5Frontier Research Center for Energy and Resources, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. 6Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan. Correspondence and requests for materials should be addressed to Y.K. (email: [email protected])Scientific RepoRts | 6:29603 | DOI: 10.1038/srepwww.nature.com/scientificreports/Figure 1. Locations of the sites used in this study. Circles represent Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) drilling sites, and squares indicate the University of Tokyo piston core sites. Sites filled in black are age-constrained and were thus used for reconstruction of the spatiotemporal distribution of independent components (ICs). White lines indicate tracks of each site, with tiny circles marking palaeopositions of each site in 5 Myr steps. Sites with red and blue labels indicate representative high-IC1 and high-IC4 sediments, respectively. Bathymetric data are from ETOPO2v2 (NOAA National Geophysical Data Center, 2006; https://www.ngdc.noaa. gov/mgg/global/etopo2.html). This map was created by using Generic Mapping Tools software (https://www. soest.hawaii.edu/gmt/), Version 4.5.8 59, and GPlates software30,31 (http://www.gplates.org), Version 1.2.0.Although application of traditional multivariate statistical analyses such as Principal Component Analysis (PCA) or Factor Analyses (FA) to geochemical data can be insightful, these methods have limitations for use and cannot be applied to certain datasets such as those discussed here. Both PCA and FA transform the data using only the mean and variance, or first- and second-order statistics. This implies that the extracted new variables, known as principal components or common factors, are mutually independent in the true sense only when the observed data constitute a multivariate Gaussian distribution9. In fact, the sediment data of the Pacific and Indian oceans exhibit large skewness and multimodal distributions (Supplementary Fig. S1); therefore, application of PCA or FA to extract independent features is not necessarily appropriate10,11. The aforementioned constraints notwithstanding, a number of previous works have demonstrated fruitful results by applying multivariate analyses to datasets of tens to hundreds of samples. Here, we build upon these studies of marine sediments and expand our perspective to examine global-scale features by using a new statistical approach on a massive geochemical dataset. We construct a hemisphere-scale compositional dataset of 3,968 bulk sediment samples from 82 sites in the Pacific Ocean and 19 sites in the Indian Ocean (Fig. 1). Moreover, we employ Independent Component Analysis (ICA) to identify the geochemical signatures hidden in the huge dataset of deep-sea sediments. ICA is a relatively new computational statistical technique established in the fields of neuroscience and information science during the past quarter century9; its utility has also been recognised in the geochemical field2,11?5. ICA can extract original independent source signals from observed signals on the basis of a fundamental assumption that the observed data consist of mutually independent source signals showing non-Gaussian distributions9. As the result of ICA, the original multi-elemental data can be expressed by a combination of independent c.
