Organic geochemistry and micropaleontology are used to determine the origin of sapropel S1 in the Aegean Sea. Low-molecular-weight (C15, C17 and C19) n-alkane data show that net primary productivity (NPP) increased from ~14,000 to 10,000 yr BP at the glacial interglacial transition, but the onset of S1 at 9600 yr BP marks a sharp decline in NPP, which remained low until ~8200 yr BP. The start of sapropel deposition is marked by increased total organic carbon (TOC) and pollen-spore concentrations, together with increased high-molecular-weight (C27, C29, C31 and C33) n-alkanes. Pollen assemblages show large influx of tree pollen from central-northern European forests. Increases in high-molecular-weight n-alkanes suggest greater influx of fresh vascular plant material at the start of S1, although the amount is small compared to other insoluble organic matter. Palynologicai studies showed that most of this insoluble organic matter are flocks of dark-brown amorphous kerogen, typical of terrigenous humic compounds. From ~8200 yr BP to the top of S1 at ~6400 yr BP, there is a decline in high-molecular-weight n-alkanes and terrigenous kerogen, and an increase in low-molecular-weight n-alkanes, suggesting that NPP recovered during the later deposition of S1 in the Aegean Sea. The increase in low-molecular-weight n-alkanes coincides with the recovery of coccolithophores and dinoflagellates, suggesting that these phytoplankton are primarily responsible for the low-molecular-weight n-alkane variations. These data from the Aegean Sea support the model for sapropel deposition resulting from increased influx of TOC during times of stagnant bottom water, but disagree with Mediterranean models prescribing a large increase in marine productivity.
Bibliographical noteFunding Information:
We thank Prof. Dr. Erol Izdar, the director of the Piri Reis Foundation for Maritime and Marine Resources Development and Education, and Prof. Dr. Orhan Uslu, the director of the Institute of Marine Sciences and Technology, for their continual support and encouragement. We further thank the officers, crew and scientific personnel of the R.V. Koca Piri Reis for their assistance in core collection. We extend our special appreciation to Linda Winsor and Jeff Hunt for their assistance in organic geochemical and isotopic analyses. We acknowledge research funds from the Natural Sciences and Engineering Research Council of Canada to Aksu (OGP0042760) and to Abrajano (OGP0121709) and from the Geological Survey of Canada to Mudie (Project # 930067). Richard Hiscott of the Department of Earth Sciences, Memorial University of Newfoundland critically read the manuscript and provided many valuable comments.
- Aegean Sea
- Fatty acids
- Sapropel S1
ASJC Scopus subject areas
- Geochemistry and Petrology