Modern foraminifera from coastal settings in northern Argentina: implications for the paleoenvironmental interpretation of Mid Holocene littoral deposits

  • Cecilia Laprida Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
  • Damián Diego Enrique Chandler Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, Ciudad Autónoma de Buenos Aires, Argentina
  • Josefina Ramón Mercau Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
  • Rubén Alvaro López Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
  • Silvia Marcomini Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Keywords: benthic foraminifera, modern beaches, paleoenvironmental reconstruction, Holocene, Argentina.

Abstract

In Buenos Aires coasts, sedimentary processes were particularly active during the Quaternary owing to eustatic fluctuations in sea level. As a result, during the late Quaternary transgressions, marine and marginal marine sediments were deposited in the coastal plain. In order to interpret these Holocene littoral sequences, we analyzed the distribution, diversity, species composition and taphonomic features of total benthic foraminifera assemblages from modern littoral settings, from the top of the dune to the lower shoreface, in two close but geomorphologically different transects located in the Atlantic coast of Northern Buenos Aires Province (Argentina, South America). Total benthic foraminiferal assemblages from subtidal and supratidal environments are distinguishable in terms of composition, diversity and taphonomic features. In upper shoreface, foreshore, backshore and foredune environments, assemblages are clearly dominated by three species: Buccella peruviana, Ammonia beccarii and Elphidium discoidale (the BAE group). This feature is the result of taphonomic processes that favor the selective preservation of such species. The study of taphonomic modifications of shells in modern assemblages allows a better discrimination between subenvironments than the analysis of taxonomic composition. Although Holocene assemblages have no strict counterparts between total modern assemblages, taxonomic composition and taphonomic modification of shells allow us to infer that the Holocene sequence was deposited between the upper shoreface and the backshore.

Published
2018-01-05
Section
Articles