Marine chronology based on 14C dating on diatoms proteins

Abstract

We present a new method of obtaining radiocarbon dates for proteins intrinsic to diatom frustules (sillafin). By asserting age models for sediment core samples that lack calcium carbonate, this method will improve interpretations of diatom-based paleoproxies for either marine or lacustrine. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, diatoms were concentrated from core sediment samples. The diatoms frustules were freed of any surface-bound organic matter, through chemical and physical treatments that will be discussed later in this paper. Compounds intrinsic to diatoms frustules were released from their opal matrix by HF dissolution. This method differs from approaches based on specific compound extractions from complex organic mixture by preparative chromatography because we eliminated most of the contaminated organic matter. The advantage of our method is that it does not require heavy cost investment and it can be added to a preparative chromatography protocol to ensure dating reliability. This method was applied to samples from a marine core collected in the Southern Ocean, that spans the last climatic cycle. We report on the radiocarbon dating results obtained on organic matter at each step of the chemical treatment, from bulk to sillafin and their interpretation.