Numerical relationships between magnetic parameters measured in Quaternary sediments and global paleoclimatic proxies
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The complexity of most geological and geophysical problems prompts sometimes the use of non linear mathematical methods to handle them. An adaptive neuro fuzzy inference system (ANFIS) that combines fuzzy logic with neural networks, is applied here to study a paleoclimate section from the Quaternary sedimentary fill of the Lake Mucubají (western Venezuela). The purpose of this work is to find a set of numerical relationships that could predict the possible connections between oxygen isotope (δ18O) values from two different locations in the northern hemisphere (Ammersee in southern Germany and an ice core from the Greenland Ice Core Project — GRIP) and rock-magnetic parameters measured in Mucubají samples (i.e. mass-specific magnetic susceptibility — χ, magnetic remanence S-ratio, mass-specific saturation isothermal remanent magnetization — SIRM and anhysteretic remanent magnetization — ARM). The best inferences in terms of coefficient of determionation R2 and the Root Mean-Square Error (RMSE) are obtained using those magnetic data as input that include information about magnetite grain size distributions, e.g., SIRM and ARM in FIS structures [1χ, 4ARM] and [4ARM, 1SIRM]. A comparison between Ammersee and GRIP actual data, as well as their corresponding inferences for the FIS structure [4ARM, 1SIRM], reveals a reasonable good inference of global trends for both records, overlooking the regional and/or local paleoclimate forcings that might have affected Ammersee. A better correlation between global isotope paleoclimate records and magnetic proxies, is perhaps prevented by the role played by local and regional paleoclimate and tectonism in Mucubají. We also argue that the ratio of ARM over SIRM appears to be related in a complex way to the onset and to the end of the Younger Dryas. Our novel approach to the assessment of a specific paleoclimate case study shows the potential of the ANFIS technique in solving problems where traditional univariate and multivariate linear regression methods could prove inadequate.
KeywordsHolocene Neuro Fuzzy System paleoclimate rock magnetic properties
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- Alexander I., Kroon D. and Thompson R., 1993. Late Quaternary paleoenvironmental change on the northeastern Australian margin as evidenced in oxygen isotope stratigraphy, mineral magnetism and sedimentology. In: McKenzie J.A., Davies P.J., Palmer-Juslon A. et al. (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 133, College Station, TX (Ocean Drilling Program), 129–161, DOI: 10.2973/odp.proc.sr.133.224.1993.Google Scholar
- Da Silva A., Costanzo-Álvarez V., Hurtado N., Aldana M., Bayona G., Guzmán O. and López-Rodríguez D., 2010 Study of a possible correlation between Miocene global climatic changes and magnetic proxies d18O, using neuro fuzzy logic analysis: stratigraphic well Saltarín 1A (Llanos foreland basin, Colombia. Stud. Geophys. Geod., 54, 607–631CrossRefGoogle Scholar
- Finol J. and Jing X.D., 2002. Predicting petrophysical parameters in a fuzzy environment in soft computing for reservoir characterisation and modeling. In: Wong P., Aminzadeh F. and Nikravesh M. (Eds.), Soft Computing for Reservoir Characterization and Modeling. Studies in Fuzziness and Soft Computing, 80, Physica-Verlag, Heidelberg, 183–217.CrossRefGoogle Scholar
- Gautam D.K and Holz K.P., 2001. Rainfall-runoff modeling using adaptive neuro-fuzzy systems. J. Hydroinform., 3, 3–10.Google Scholar
- Giegengack R., Grauch R.I. and Sahagam R., 1976. Geometry of Late Cenozoic displacement along the Boconó Fault, Venezuelan Andes. Boletín de Geología Publicación Especial, 7/2, 1201–1223Google Scholar
- Moreno E., Thouveny N., Delanghe D., McCave N.I. and Shackleton N.J., 2002. Climatic and oceanographic changes in the Northeast Atlantic reflected by magnetic properties of sediments deposited on the Portuguese Margin during the last 340 ka. Earth Planet. Sci. Lett., 202, 465–480.CrossRefGoogle Scholar
- Pérez O., Bilham R., Bendick R., Hernández N., Hoyer M., Velando J., Moncayo C. and Kozuch M., 2001. Velocidad relative entre las places del Caribe y Sudamérica a partir de observaciones dentro del sistema de posicionamiento global (GPS) an el norte de Venezuela. Interciencia, 26, 69–74 (in Spanish).Google Scholar
- Tahmasebi P. and Hezarkhani A., 2010. Application of adaptive neuro-fuzzy inference system for grade estimation; case study, Sarcheshmeh Porphyry Copper deposit, Kerman, Iran. Aust. J. Basic Appl. Sci., 4, 408–420.Google Scholar