The role of Holocene climate dynamics in the modeling of fluviomarine terraces in the northeastern Brazilian coast

Fluviomarine terraces comprise mixed sedimentary sequences formed through the interplay of fluvial and marine aggradational morphodynamics. Although they are very common along the vast Brazilian coast, they are currently little explored in the geomorphological literature. In recent official mappings, it is common to observe the classification of the last or predominant event in each sector of the plain, with the discussion of fluviomarine morphologies being little explored. Therefore, this study aims to analyze transitional environments near the Rio Pardo River estuary, located on the northeastern Brazilian coast, within the alluvial-coastal system, which presents complex morphosedimentary archives consolidated during the regressive trend of the Holocene Relative Sea Level. To better understand the genesis, chronology, and vertical sequence that formed these fluviomarine terraces. A morphological description of three stratigraphic profiles exposed on erosive riverbanks was conducted using optically stimulated luminescence dating, sediment grain size characterization, and environmental depositional conditions and pedogenesis process. The results suggest five distinct depositional stages occurred, driven by Holocene climatic variations in the region with close correlation with Bond events and variations of the Intertropical Convergence Zone and South Atlantic Convergence Zone: 1 - Early Holocene ~10.59 ± 0.85 ka; 2 - Middle Holocene ~5.30 ± 0.66 ka and 4.57 ± 0.48 ka; 3 - Late Holocene A ~3.44 ± 0.31 ka; 4 - Late Holocene B ~2.5 ka; 5 - Modern surface deposits ~1.93 ± 0.20; 1.59 ± 0.18 and 1.46 ± 0.1 ka. Thus, the fluviomarine terraces analyzed constituted support for the identification of the climatic pulses that occurred in the Holocene along the Brazilian northeast coast.