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The São Francisco delta in eastern Brazil is considered a classical example of a wave-dominated delta constructed in a glacial isostatic adjustment (GIA) far-field region. Although this delta is widely mentioned in the international literature, few details about its sedimentary architecture have been published. In this paper, we use a new dataset consisting of 15 boreholes and 26 radiocarbon datings to discuss the 3D architecture of the delta and the role played by GIA far-field effects in delta construction. The delta plain consists of a 10–12 m thick littoral sand sheet that progrades over a muddy subaqueous clinoform, forming a compound clinoform. Delta construction began between 8.4 and 7.2 ka BP and included a stage of normal regression that lasted until 5.7 ka BP, followed by a stage of forced regression. The transition between these two stages is marked by the highest position of the sand–mud transition in the boreholes. This forced regression is due to a 3–4-m drop in relative sea level since the mid-Holocene, which is characteristic of GIA far-field regions. Additionally, as a consequence of this drop in relative sea level, there is a progressive increase in the altitude of the beach-ridge deposits continentward, which combined with the development of extensive dune fields in the later stages of delta construction, contributes to the increased resilience of the delta to ongoing sea-level rise. The 3D architecture of the delta was strongly influenced by antecedent topography. The delta was built on a bathymetric depression on the shelf that almost entirely traps the sediment load of the São Francisco River. The uneven relief inside this bathymetric depression ultimately controlled lateral variations in the total thickness of the delta edifice. • Two-stage delta construction in GIA far-field regions: normal and forced regression. • Drop in sea level since mid-Holocene in GIA far-field regions increases delta resilience to ongoing sea-level rise. • Antecedent topography strongly controlled the delta 3D architecture. • 3D architecture of the São Francisco wave-dominated delta is presented for the first time. [ABSTRACT FROM AUTHOR]

This study aims to reconstruct the Holocene evolution of a semiarid tidal channel system in response to the deglacial sea-level rise and modern coastal processes. With a maximum water depth of approximately 10 m, this very shallow system is in the easternmost part of the Brazilian equatorial margin along a tide-dominated coast in a semidiurnal, mesotidal regime. The channel system is interconnected with the Atlantic Ocean through a tidal inlet formed by the Galinhos spit. This work comprised ship and land-based fieldwork with sedimentological and stratigraphic approaches. Four seismic units (U1-U4) and seismic horizons (H1-H4) were identified by reconstructing the stratigraphic architecture. The results show that: (1) the formation of paleochannels in the current spit may have started before the middle Holocene; (2) there was a network of pre-existing channels with a different configuration filled by units U2 and U3, constituting the transgressive and highstand systems tracts; (3) spit migration is the key factor to open and close inlets; (4) internal configuration patterns show a less energy and monotonous depositional environment above H4, within unit U4 (which started at ~5000 cal yrs. BP); (5) the current system configuration has been active since the formation of the U3 unit since the closure of the paleochannels; and (6) the Galinhos region shows progressive sedimentary infilling of a lagoon behind a coastal spit via sediment accumulation from marine sources and its ultimate transformation into a coastal swamp with tidal channels. • Holocene semi-arid tidal channel system. • Equatorial spit-barrier island system, in a semidiurnal, mesotidal regime • Identification of four Holocene units and four boundaries • Definition of the Holocene seismic architecture framework of the Galinhos tidal channels system. • Identification of transgressive, highstand and lowstand system tracts • Sedimentary infilling of a lagoon behind a coastal spit. [ABSTRACT FROM AUTHOR]