Title
Cross-stratigraphies from a seismically active mud lens off Peru indicate horizontal extensions of laminae, missing sequences, and a need for multiple cores for high resolution records
Date Issued
01 November 2014
Access level
metadata only access
Resource Type
journal article
Author(s)
Salvatteci R.
Field D.
Ortlieb L.
Ferreira V.
Baumgartner T.
Caquineau S.
Reyss J.
Sanchez-Cabeza J.
Publisher(s)
Elsevier
Abstract
Marine laminated sediments in dysoxic areas of the ocean floor are an excellent archive for high-resolution climate reconstructions. While the existence of discontinuities produced by natural events, such as underwater landslides (slumps), strong bottom currents, and/or bioturbation is usually acknowledged for long records, the extent of their influence on high-resolution sequences is usually not considered. In the present work we show strong evidence for multiple stratigraphic discontinuities in different gravity and box-cores retrieved off Pisco (Peru) covering the last 600years. Chronostratigraphies are largely based on cross-correlation of distinct sedimentary structures (determined by X-ray image analysis) and validated using 210Pb, 241Am, and 14C profiles, as well as proxy records. The cross-correlation of distinct stratigraphic layers allows for chronostratigraphic tie points and clearly shows that some sedimentary sequences are continuous across scales of tens of kilometers, indicating that regional processes often determine laminae formation. Some differences in laminae thickness were found among cores, which could be explained by different sedimentation rates, spatially variable deposition of diatom blooms, changes in silica dissolution and partial deposition/erosion caused by bottom currents. Using multiple stratigraphic tie points provides clear evidence for laminated sequences present in some cores to be missing in other cores. Moreover, instantaneous depositions from upslope were identified in all the cores disrupting the continuity of the sediment records. These discontinuities (instantaneous deposits and missing sequences) may be due to slumps, possibly triggered by earthquakes and/or erosion by strong bottom currents. In spite of the missing sequences in some cores, a continuous composite record of the last six centuries was reconstructed from spliced sequences of the different cores, which provides a well-constrained temporal framework to develop further high-resolution proxies in this region. The present work shows that paleoreconstructions developed from single cores, particularly in areas with strong seismic activity and/or strong bottom currents, are subject to both temporal gaps and instantaneous depositions from upslope, both of which could be misinterpreted as abrupt climate changes or anomalous climate events. We stress the need for multiple cores to determine the stratigraphic continuity and chronologies for high-resolution records. © 2014 Elsevier B.V.
Start page
72
End page
89
Volume
357
Language
English
OCDE Knowledge area
Biología marina, Biología de agua dulce, Limnología
Scopus EID
2-s2.0-84898037524
Source
Marine Geology
ISSN of the container
00253227
Sponsor(s)
We thank IMARPE for full support of this research. We acknowledge the crew of the RV José Olaya Balandra and other scientific participants in the box-coring survey: E. Enríquez, J. Ledesma, R. Marquina, L. Quipúzcoa, J. Solís, and L. Vásquez, without their support this research could not have taken place. We would like to thank G. Vargas for his help during the cruise “Paleomap 2006”. We also acknowledge F. Cetin for her valuable help in the %N analyses, L. Wee Kwong for the 210 Pb alpha analyses and P. Martinez for the SCOPIX images. We are grateful to R. Gingold (sweepandmore.com) for constructive ideas and proof-reading the manuscript. The AMS radiocarbon measurements were obtained by the “Laboratoire de mesures de C-14” LMC14 (UMS 2572, CEA-CNRS-IRD-IRSN-Ministère de la Culture), Gif-sur Yvette, France, through the IRD financial and technical support to this laboratory. We also acknowledge the Laboratoire des Sciences du Climat et de l'Environnement (CNRS-CEA-Univ. St Quentin en Yveline, in Gif-sur Yvette, France) for gamma counting and the Marine Environment Laboratories of the IAEA (International Atomic Energy Agency, Monaco) for alpha analyses. We acknowledge support from the project PALEOMAP, the IAEA Coordinated Research Project 12789 (Nuclear and Isotopic Studies of the El Niño Phenomenon in the Ocean), the PALEOTRACES project, the PALEOPROXUS project and the Chaire croisée PROSUR. The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco. We especially acknowledge Lutz Reinhardt for his valuable comments that greatly improved this manuscript.
Sources of information: Directorio de Producción Científica Scopus