Reconstruction of the last deglaciation: deconvolved records of $\delta^{18}$O profiles, micropaleontological variations and accelerator mass spectrometric $^{14}$C dating

• Published in: Climate Dynamics
• Main Authors: Bard, E., Arnold, M, Duprat, J, Moyes, J, Duplessy, J-C
• Other Authors: Centre des Faibles Radioactivités, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Département de Géologie et d'Océanographie Talence (DGO), Université Sciences et Technologies - Bordeaux 1 (UB), Formations géologiques profondes (FGP), ANDRA-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1987
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Planktonic foraminifera
• Online Access: https://hal.science/hal-03549609; https://doi.org/10.1007/BF01054479

International audience Bioturbation acts as a low-pass filter in displacing and reducing the amplitudes of stratigraphic signals. This often leads to a loss of high-frequency events in thestratigraphic record. In addition, when considering an isotopic signal ($\delta^{18}$O, $^{14}$C) measured in stratigraphic "carriers", such as foraminifera, bioturbation and carrier abundance changes can create artifacts which may be falsely interpreted as leads or lags in the paleoclimati c record. We present here a model in which bioturbation is treated as a time-invariant filter whose impulse response function (IRF) is like that of a first-order system. The method involves first deconvoluting the abundance curves of the carriers and then the isotopic signals using the restored "carrier" abundances. This analysis was initially used toartificially generate ideal curves, with the aim of qualitatively modelling the effects ofbioturbation. Following this, deconvolved curves were obtained using data from the core CH73-139C using $\delta^{18}$O, A.M.S. C-14 ages, and abundances of two planktonic foraminifera: $G.bulloides$ and $N.pachyderma$ left-coiling. A comparison of the data with the unmixed curves enables separation of the bioturbation artifacts and the construction of a common deglaciationcurve based on the restored signals. Importantly, the model emphasizes some severe limitations of mathematical analysis of stratigraphic signals.