Paleoenvironmental and climatostratigraphic insights for Marine Isotope Stage 19 (Pleistocene) at the Montalbano Jonico succession, South Italy

Quantitative analyses on pollen and ostracods were performed on the Montalbano Jonico succession (MJS) through Marine Isotope Stages (MIS) 18-21 in order to acquire details of paleoenvironmental changes and climate pattern during MIS 19, which includes the Matuyama-Brunhes paleomagnetic boundary (MBB). While the MJS does not record the MBB, which is the main criterion for defining the Early-Middle Pleistocene boundary, it is a candidate Global Boundary Stratotype Section and Point (GSSP) for the Ionian Stage and Middle Pleistocene Subseries because of its excellent exposure, continuous deposition, and astronomically tuned record between MIS 37 and MIS 16. The new 40Ar/39Ar age of 773.9 ± 1.3ka for volcaniclastic layer V4 allows the age-model for the succession to be refined. Ostracod assemblages show significant paleodepth fluctuations at the glacial-interglacial scale, in agreement with the pollen distality index (Pinus vs. Caryophyllaceae, Amaranthaceae and Ephedra) which also suggests higher values during MIS 19. Pollen analysis provides supplementary paleoclimate data that are valuable to reconstruct temperature variation during the identified phases. A major expansion of steppic vegetation at 790ka in the uppermost MIS 20 correlates with a significant cold and arid Northern Hemisphere climate phase, as documented by a concurrent peak both in North Atlantic ice rafted debris and Mediterranean dust records. Climate conditions recorded in MIS 19.3 were similar to those of the present interglacial, whereas a dry climate phase marks MIS 19.2 at 771.84ka, slightly above the V4 layer. Millennial scale climate variability occurred during MIS 19 as evidenced by two abrupt short-term moderately dry pollen events at 783.5ka and 774.8ka that could be related to a period of reduced geomagnetic field intensity through the MBB transition. Additional environmental/chronological events accompanied this stratigraphic interval: i) the volcaniclastic layers V3 and V4, radiometrically dated at 801.2 ± 19.5ka and 773.9 ± 1.3ka, respectively; ii) the co-occurrence of maximum flooding and thermal maximum in agreement with the previously recorded co-occurrence of the Neopycnodonte community and tropical-subtropical mesopelagic teleostean Bonapartia pedaliota, close to the increase of Quercus; and iii) the maximum depth (MD) between 777.3 and 773.25ka as recorded by outer shelf/upper slope macroinvertebrate fauna, close to the highest value of pollen distality index in MIS 19. Results enhance the understanding of orbital-suborbital paleoenvironmental change during the mid-Pleistocene, and particularly of the climate pattern during MIS 19 and across the MBB.