Complex coastal change in response to autogenic basin infilling: An example from a sub‐tropical Holocene strandplain

摘要: Thick bay-fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground-penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions hydrodynamic modelling to explore the role autogenic processes – notably a reduction wave energy response coastal embayment infilling evolution shoreline morphodynamics. Following regional 2 4 m highstand at ca 5·8 ka, 75 km2 Tijucas Strandplain southern Brazil built from fluvial sediments deposited into semi-enclosed bay. Holocene regressive deposits are underlain by sands Pleistocene transgressive–regressive sequence, backed barrier-island. The immediately 5 16 m seaward-thickening, fluvially derived, Holocene-age, basin-fill mud. Several trends observed landward (oldest) seaward (youngest) sections strandplain: (i) upper shoreface foreshore become finer thinner shift sand-dominated mud-dominated; (ii) beachface slopes decrease >11° 7°; (iii) progradation rates increase 0·4 1·8 m yr−1. Hydrodynamic demonstrates correlation progressive shoaling Bay driven sea-level fall onshore wave-energy transport 18 4 kW m−1. combination allogenic (sediment supply, falling relative geology) (decrease due bay shoaling) drove system with characteristics rare, if not unique, rock records. These findings demonstrate complexities architecture styles systems tracts. Furthermore, this article highlights diverse feedbacks responsible for these intricate marginal marine systems.