Preliminary cyclostratigraphy on planktonic foraminifera from IODP-Hole U1406A

Cyclostratigraphy reconstructs astronomical-periodic signals in quantitative data from climate-sensitive proxies, as microfossils, carbonate content, isotopic data or any physical properties measurable at sufficient resolution. The astronomical cycles strongly influence the climate changes at a long time scale. The deep link between climate, sedimentation and orbitally forced insolation can be detected at a smaller scale and it allows the tuning of sedimentary sequences using foraminifera. This study investigated the interval 23.40-21.17 Ma within IODP Site U1406 in the North Atlantic Ocean, detecting periodicities longer than 40 Ky. The spectral analysis on Paragloborotalia siakensis, Globigerina bulloides, Globoturborotalita and Catapsydrax provided the most reliable results, All signals resulted stronger in the upper portion of the succession and weaker in the lower one, highlighting problems on the first paleomagnetic age model of this site. Paragloborotalia siakensis shows the strongest correspondence with the 110 Ky, 400 Ky and 1.2 Ma eccentricity cycles. Thus, it was selected to elaborate the second age model. Iteratively using the 400 Ky periodicity as an additional checking tool, the P. siakensis filtered curve has been adjusted to achieve the final age model, correlating each peak of its distribution to the eccentricity curve Laskar2004. The abundance of G. bulloides seems paced by 110 Ky, 400 Ky and 1.2 Ma eccentricity cycles in antiphasic relation to P. siakenisis. Globigerina bulloides and Trilobatus group show unexpectedly a similar sensitivity to astronomical cycles, possibly explained by different paleoecological affinity of T. primordius in respect with the other taxa of the Globigerinoides plexus.