Reconstruction of the last deglaciation: deconvolved records of δ18O profiles,micropaleontological variations and accelerator mass spectrometric14C dating

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 the stratigraphic record. In addition, when considering an isotopic signal ¹⁸O,¹⁴C 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 paleoclimatic record.We presenthere a model in which bioturbationis 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 to artificially generate ideal curves, with the aim of qualitatively modelling the effects of bioturbation. Following this, deconvolved curves were obtained using data from the core CH73-139C using ¹⁸O, A. M. S. C-14 ages, and abundances of two planktonic foraminifera:G. bulloides andN. pachyderma left-coiling. A comparison of the data with the unmixed curves enables separation of the bioturbation artifacts and the construction of a common deglaciation curve based on the restored signals.Importantly, the model emphasizes some severe limitations of mathematical analysis of stratigraphic signals.