XRF analysis of Laguna Pallcacocha sediments yields new insights into Holocene El Niño development

Samuel Z. Mark, Mark B. Abbott, Donald T. Rodbell, Christopher M. Moy

Research output: Contribution to journalArticlepeer-review

Abstract

The laminated sedimentary sequence of Ecuador's Laguna Pallcacocha is one of the most widely cited proxy records of Holocene El Niño Southern Oscillation (ENSO) variability. Previous efforts to reconstruct flood-driven laminae from Laguna Pallcacocha relied solely on sediment color, a useful but non-specific metric of flood events. We improved the chronology with 210Pb and additional 14C dates over the past millennium, which allows for comparison of the sedimentary record with historically documented El Niño events. Additionally, we use elemental composition derived from X-ray Fluorescence (XRF) to reconstruct flood history at Pallcacocha. A principal component analysis (PCA) of the XRF dataset identifies minerogenic flood-driven clastic laminae. The first principal component (PC1) of the XRF data and red color intensity are positively correlated over the past 7.5 kyr, but the color record fails to capture high frequency variability that is preserved in the XRF dataset during the early Holocene (approximately 7.5-11 kyr BP). The new XRF dataset indicates moderate El Niño activity during the early Holocene, suppressed El Niño activity in the middle Holocene, and enhanced El Niño activity during the late Holocene. This pattern is relatively common among other ENSO records, and has been attributed to long-term changes in tropical insolation. Some intervals-most notably between 3-2 kyr BP and during the last millennium-deviate from expected trends if insolation was the sole forcing mechanism. Previously proposed mechanisms linking ENSO to latitudinal displacement of the ITCZ and ocean-atmospheric variabilities in other ocean basins appear to play an additional role in modulating Holocene ENSO development, as demonstrated by statistically significant correlations between the revised Laguna Pallcacocha flood history and proxy records from the Atlantic.

Original languageEnglish (US)
Article number117657
JournalEarth and Planetary Science Letters
Volume593
DOIs
StatePublished - Sep 1 2022

Bibliographical note

Funding Information:
We would like to thank two anonymous reviewers whose input greatly improved the quality of this manuscript. This project was funded by the National Science Foundation (grant number # 502227 ), the University of Pittsburgh Department of Geology and Environmental Science, the University of Pittsburgh Climate and Global Change Center, and the Union College Geology Department. This work was also made possible by the Continental Scientific Drilling (CSD) Facility X-ray Fluorescence Lab at the University of Minnesota Duluth's Large Lakes Observatory, funded by the National Science Foundation (grant # 502227 ).

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • ENSO
  • flood history
  • Holocene
  • paleolimnology
  • tropical Pacific
  • XRF

Continental Scientific Drilling Facility tags

  • 68

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