Integrated stratigraphy of the Ludlow (Silurian) of the Baubliai-2 core (western Lithuania) and the record of δ18O and δ13C climatically driven co-variability

Ludlow Epoch of the Silurian Period is a key point in understanding evolution of marine biota and large scale climate perturbations. Here we present an integrated record of graptolites, δ13C, and δ18O of carbonates from a deep shelf section of the south-eastern part of the Silurian Baltic Basin. Graptolite record allows us to distinguish ludensis (?), nilssoni, scanicus, leintwardinensis and tenuis graptolite biozones, and the δ13C trend shows ascending portion of the mid-Ludfordian excursion. In addition we investigated the time specific variability in δ13C, and δ18O and their interaction. Cross-correlation analysis revealed a significant interaction between these variables, where δ18O driven δ13C. Spectral and recurrence quantification analyses revealed that the variability in δ18O is characterized by a very distinct periodicity with period length of approximately 1 Myr, which putatively interpreted here as representing climatic signal of long-period amplitude modulation of obliquity. The presented data confirm the importance of grand Milankovitch cycles in the pacing of geobiological change during the late Silurian