『Abstract
　In this study, organic carbon to organic phosphorus (Corg/Porg) and total phosphorus (Corg/Ptot) ratios as bottom water redox proxies are explored for two eastern Mediterranean sediment records extending back 〜600-700 kyrs. Cores KC19C (19.6 m long, 2750 m water depth) and KC01B (37.0 m long, 3643 m water depth) contain numerous organic-rich layers (sapropels). Throughout the two cores, variations found in the Corg/P ratios correspond to those for other redox proxies such as total S contents and V/Al ratios. Accordingly, these are interpreted as variations in bottom water oxygenation and inter-sapropel redox variability. In core KC19C, the original Corg/P signals seem to have been preserved despite intense post-depositional sulfidization. High-resolution P fractionation data of sapropel S5 from a third core (PS25PC, 3304 m water depth) showing high and relatively stable Corg/Porg ratios, indicate that sapropel S5 at this deep location was deposited under permanently reducing conditions. While P regeneration from organic matter was intense, net P burial increased in the sapropel due to enhanced burial of inorganic calcium phosphate, likely biogenic Ca-P. Sediment P contents and Corg/Ptot ratios in S5 are variable, reflecting short-term changes in marine conditions (productivity/redox) and sediment chemistry. The Corg/Porg and Corg/Ptot ratios thus provide valuable insight into paleoceanographic conditions and pathways of P cycling for (Mediterranean) sediment records extending back at least 〜600-700 kyrs.

Keywords: Phosphorus; C/P ratio; Redox proxy; Sapropel; S5; Mediterranean』

1. Introduction
2. Materials and methods
　2.1. Core material
　2.2. Solid phase bulk analyses
　2.3. Phosphorus fractionation
　2.4. Fish debris counts
3. Results
　3.1. Bulk geochemistry of cores KC19C, KC01B and PS25PC
　3.2. Phosphorus fractionation in cores PS25PC and KC19C
4. Discussion
　4.1. Stability of Corg/P ratios on Quaternary timescales
　4.2. Sediment Corg/P ratios: redox conditions and P cycling during sapropel formation
　4.3. Redox conditions and phosphorus cycling during formation of sapropel S5
5. Conditions
Acknowledgements
References