Characterization and Evolution of Tropical Barrier Island Systems on the Northern Coast of the State of Rio Grande do Norte, NE Brazil
Cores; Barrier Islands; Spits; Sedimentary Sequence.
The north coast of the state of Rio Grande do Norte is classified as a mixed energy tropical coast and presents a very intense coastal dynamic. Within this context, the presence of a system of barrier islands stands out – sandy spits, which are sandy bodies arranged parallel to the coastline, which isolate areas protected from the impact of the open sea and present different sedimentary deposits. From this perspective, the characterization and analysis of this system, having knowledge about the processes that act in these environments and their sedimentary/stratigraphic configuration is of paramount importance both for environmental studies and reservoir analogues. The main objective of this study was to characterize the barrier island systems/sandy spits on the northern coast of the state, close to the city of Macau/RN. The research included data from surface samples, cores of sedimentary material, collected in the sub-environments of the barrier island/sand point system, and interferometric bathymetry of tidal channels. 6 sedimentary facies were identified in the cores that were related to tidal channel deposits, tidal flat, tidal channel point bar, beach/barrier island, eolian sand and washover. The similarity between the characteristics of the surface samples and the facies described in the cores helped in the interpretation of the subenvironment associated with each of the facies. In bathymetry, the channels presented depths between 1.3 and -6.3 m, the main channel in a “U” shape, and sandy/muddy banks
were identified on the banks of the channel, in addition to two regions with 2D and 3D underwater dunes , small to large. In this highly dynamic system, the analyzed cores showed variations in the sedimentary record, indicating the change from one deposit to another, depending on their position within the system of barrier islands and tidal channels. Finally, correspondences were observed in the sequence of deposits presented by cores acquired in 1991 with cores collected in 2019, which suggests that the same processes and events that caused the deposition of these sediments occur in a similar way today.