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Gondwana Research, 86, 222–249p. (2020) DOI:10.1016/j.gr.2020.05.015
The upper Silurian, and especially Pridoli epoch is a critical interval for the understanding the evolution of Earth's biota, since it witnessed series of powerful extinction events, global reorganizations of paleocommunities, and expansion of new clades, which assumed dominance in the subsequent Devonian period. The stratigraphic record of the eastern part of the Silurian Baltic Basin represents an excellent candidate for the fine scale analysis of paleoecological and paleoceanographic dynamics. Therefore we presenting here stratigraphic record of the Milaičiai-103 core (south western Lithuania) of conodonts, brachiopods, δ13Ccarb, δ18Ocarb and a series of various geochemical and geophysical proxies, most of which were sampled at a very high resolution ( 11 Ka), spanning uppermost Ludlow, Pridoli, and the lowermost Devonian. The analysis revealed that the Pridoli was characterized by four distinct long-term dynamic states here named: i) Normal Pridoli I, ii) Šilalė negative carbon isotopic excursion and extinction event, iii) Normal Pridoli II, and iv) Klonk positive stable carbon isotopic event and excursion. The most significant change in most variables is detected approximately in the middle of the Pridoli, at the beginning of the Delotaxis detorta Zone, at the recovery after Šilalė event of conodonts, and at the onset of collapse of brachiopod communities. The analysis of dynamic complexity revealed the strong evidence for the presence of 405 Ka metronome Milankovitch cycles in the record of δ13Ccarb, which constrains the duration of the Pridoli epoch to 4.3 ± 0.2 Ma. The recurrence plot analyses revealed deterministic coordination between δ13Ccarb and conodont paleocommunity dynamics at all scales. Finally lead-lag analysis, using conditional joint recurrence, revealed that conodont dynamics, as a rule, were driven by perturbations in the carbon cycle, although Šilalė event interval shown opposite pattern, thus confirming the unusual nature of this previously unrecognized coordinated climatic and biotic event.
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