Timing of the last sequence boundary in a fluvial setting near the highstand shoreline - Insights from optical dating

Torbjorn E. Tornqvist*, Jakob Wallinga, Freek S. Busschers

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

55 Citations (Scopus)

Abstract

We investigated, by means of optical dating, the chronostratigraphic nature of the sequence boundary associated with the last glacial in a sandy to gravelly compound paleovalley fill, just landward of the highstand shoreline in the Rhine-Meuse Delta (Netherlands). Laterally extensive fluvial strata deposited during oxygen isotope stage 4, coeval with a major sea-level fall, unconformably overlie estuarine deposits from stage 5 or fluvial deposits from the penultimate glacial (stage 6). These chronostratigraphic relationships differ substantially from widely used models and indicate (1) that sequence-boundary formation in this setting was associated with the onset of pronounced sea-level fall, shortly after 80 ka; (2) that the time gap represented by the sequence boundary may be extremely small (<10 k.y.); (3) that the age of the sequence boundary may decrease both updip and downdip of the highstand shoreline; and (4) that our study does not provide viable diagnostic criteria for a sea-level-controlled sequence boundary above the falling-stage systems tract. Despite the high-frequency, high-amplitude glacio-eustatic regime that might be considered ideal for the formation of an unambigous unconformity, the last sequence boundary in this setting is commonly cryptic.

Original languageEnglish
Pages (from-to)279-282
Number of pages4
JournalGeology
Volume31
Issue number3
DOIs
Publication statusPublished - 1 Mar 2003
Externally publishedYes

Keywords

  • Optical dating
  • Quaternary
  • Rhine-Meuse system
  • Sequence stratigraphy

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