Holocene evolution of Patos Lagoon, Brazil: The role of antecedent topography

Eduardo Calixto Bortolin, Jair Weschenfelder, Andrew Cooper

Research output: Contribution to journalArticle

Abstract

The Patos Lagoon in Rio Grande do Sul, Brazil, is part of the largest barrier lagoon system in the world. It is enclosed by
a 400-km-long composite late Pleistocene/Holocene sandy barrier and has a single tidal inlet. The modern lagoon is
shallow (average , 5 m) and is dominated by silt deposition. More than 1000 km of shallow seismic data (3.5 kHz)
indicate that the lagoon is underlain by several shore-normal incised valleys separated by interfluves. Each incised
valley existed as an individual estuary since its first flooding during the mid-Holocene. The infill of these valleys contains
a basal fluvial unit, a central estuarine mud unit, and locally developed tidal sand bodies associated with former tidal
inlets. The contemporary lagoonal sediments form a blanketing upper unit. Ultimately, the interfluves were drowned
and the contemporary lagoon was formed by the coalescence of the incised valley estuarine systems in the late Holocene.
This expansion of accommodation space coincided with a dramatic reduction in vertical sedimentation rates. Seismic
profiling reveals the contemporary sandy spits, and their subaqueous extensions coincide with the location of former
interfluves, indicating that inherited topography exerts major control over the location and development of lagoonmarginal
spits.
Original languageEnglish
Pages (from-to)357-368
JournalJournal of Coastal Research
Volume35
Issue number2
DOIs
Publication statusPublished - 1 Mar 2019

Keywords

  • Paleotopography
  • paleovalleys
  • coastal plain

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