U- and Th-series disequilibria in coastal infill sediments from Praia da Rocha (Algarve Region, Portugal): a contribution to the study of late Quaternary weathering and erosion

H. M. Roberts, A. J. Plater

Research output: Contribution to journalArticlepeer-review

17 Citations (SciVal)

Abstract

U- and Th-series disequilibria observed in a sequence of infill sediments from Praia da Rocha, southern Portugal, were used in combination with geochemical and particle size data to investigate sediment provenance with a view to resolving the late Quaternary weathering and erosion history of the Algarve region, and the stratigraphy of coastal karstic exposures of the Faro/Quarteira (FQ) formation. The red infill units can be distinguished from the brown and buff units on the basis of their lower residual U- and Th-concentrations, their differing post-depositional histories (as revealed by U- and Th-series disequilibria in sequentially extracted sediment phases), and their greater degree of sediment processing. Hence, the buff and brown infill units appear to be derived locally from weathering of the Miocene limestone whilst the red infill may be linked to large-scale mass movement of the FQ formation from further inland, but south of Silves, during the Late Pleistocene. This sequence of events confirms a close association between the formation of karst topography and infilling by gravitational slumping, debris flow and fluvial activity, and, hence, accounts for the complex (three-stage) sediment provenance of the infill material.

Original languageEnglish
Pages (from-to)223-238
Number of pages16
JournalGeomorphology
Volume26
Issue number4
DOIs
Publication statusPublished - Jan 1999

Keywords

  • URANIUM
  • Praia da Rocha
  • U-series
  • ALPHA-RECOIL
  • LOW-TEMPERATURES
  • WATERS
  • THORIUM
  • Th-series
  • ISOTOPES
  • RADIONUCLIDES
  • ADSORPTION
  • Late Quaternary
  • SOUTHERN PORTUGAL
  • SORPTION

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