Sediments from around the lower younger dryas boundary (se arizona, usa): implications from la‐icp‐ms multi‐element analysis

Abstract

One of the prominent features in sediment sequences formed around the Allerød‐Younger Dryas transition (c. 12.9–12.8 ka bp) in North America is a dark layer of organic‐rich material, i.e. the black mat. The black mat sequences in southeast Arizona contain a thin sandy basal layer corresponding to the lower Younger Dryas boundary. Trace element concentrations in the lower Younger Dryas boundary sediments, in the black mat, in the host sediments, and in charcoal from Western Europe and southeast Arizona were studied using LA‐ICP‐MS. The black mat samples and samples of the underlying host sediments display compositions similar to the average continental crust, while the sediments from the lower Younger Dryas boundary are enriched in rare earth elements, Ni, and Co whereas Ta, Nb, Zr, and Hf are depleted relative to the rare earth elements. Such a difference in compositions between the lower Younger Dryas boundary sediments and other sediments points to a short enigmatic event, which changed conditions of sedimentation just before the onset of the Younger Dryas cooling. The presence of products of biomass burning of still unknown origin is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary.

Key words:

• sediments
• trace elements
• Younger Dryas

Acknowledgements

The authors thank D.S. Lauretta for provided opportunity to work in the LPL cosmochemistry laboratory. R.J. Maxwell and J.S.M. Ballenger are thanked for help with fieldworks. J.S.M. Ballenger is also thanked for providing us with the Palominas samples. P. Bertran is thanked for providing us with samples from SW France. We thank J.S.M. Ballenger, C.V. Haynes Jr, A. van Hoesel, W.Z. Hoek, M. Drury, E. Rudnickaitė, D. Subetto, and C. Verbruggen for the fruitful discussion of the obtained results. Two anonymous reviewers are thanked for reading the earlier version of the manuscript, and for invaluable comments and suggestions. I. Fay Barton is thanked for checking English. This study was supported in part by the NAI International Collaboration Fund for AVA.

Additional information

Notes on contributors

Alexandre V. Andronikov

Alexandre V. Andronikov, Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ 85721, USA Email: [email protected]

Irina E. Andronikova

Irina E. Andronikova, Lunar and Planetary Laboratory, University of Arizona, 1415 N. 6th Ave., Tucson, AZ 85705, USA Email: [email protected]