Geochemical mapping based on geological units: a case study from the Marnoso-arenacea formation (Northern Apennines,Italy) |
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| Affiliation: | 1. Department of Geology and Geophysics, University of Hawai‘i at Mānoa, 1680 East-West Road, POST 517A, Honolulu, HI 96822, USA;2. Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, USA;3. Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France;4. The Meteorite Market, Port Townsend, WA, USA;1. Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Nomi, Ishikawa 923-1224, Japan;2. National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama 236-8648, Japan;3. Japan Marine Science Foundation, Minato, Mutsu, Aomori 035-0064, Japan;4. Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan;5. Marine Ecology Research Institute, Yamabuki, Shinjuku, Tokyo 162-0801, Japan;6. Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho, Hakodate 041-8611, Japan;1. CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China;1. Helmholtz—Centre Potsdam, German Research Centre for Geosciences, Section 3.4 Fluidsystemmodellierung, 14473 Potsdam, Germany;2. Helmholtz—Centre for Environmental Research—UFZ, Dept. Catchment Hydrology, 06120 Halle/Saale, Germany |
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| Abstract: | Geochemical maps can provide us with much information on geology, earth surface processes and anthropogenic pressure and are valuable tools for ore prospecting and land management. Stream sediments represent an integral of the various possible sources of sediments upstream from the sampling point therefore there can be multiple signal sources but generally the prevailing signal source is the one related to bedrock geology. Stream sediments collected from active second-order channels including singular geological units, were selected in order to determine the geochemical characteristics of each unit. The aim of this study was to analyze their potential for using them to integrate geological interpretation and produce a geologically-oriented geochemical map. From the 770 samples collected for a regional geochemical mapping program, we selected 149 samples whose catchment basin included only one of the members recognized within the Marnoso-arenacea formation. This middle–upper Miocene (Langhian–Tortonian) turbiditic unit forms the backbone of the Romagna Apennines and has been subdivided into 14 members according to age and lithostratigraphic criteria. The results indicate that there are marked differences in the composition of the members of the Marnoso arenecea formation which indicate the provenance of the sediment and the palaeogeographic evolution of the units. By means of univariate and multivariate statistical analyses (Factor analyzes) two main types of sediment compositions are identified: Tortonian members are characterized by sialic coarse grain-sediments while the Langhian–Serravallian members are richer in carbonate fraction, slightly enriched in a mafic contribution. This study elaborated the geochemical data from a geological point of view by integrating the information available in literature to spatially extend the interpretation based on limited site observation as for petrographic studies. In general, the geochemical map based on a geological unit could be a useful tool for carrying out the geological reconstruction of a complex area. |
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| Keywords: | Geochemical mapping Geochemistry Stream sediments Provenance R-mode factor analysis Marnoso-arenacea formation Geological members Sediment composition Source rock weathering Apennines |
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