ABSTRACT

In an attempt to discriminate different sources of organic matter and reconstruct the paleo-environment of the Taipei Basin, northern Taiwan over the past 250,000 years, organic carbon and nitrogen content (C/N ratios) and isotope composition (δ¹³C and δ¹⁵N) are measured for sediment samples collected from core Wu-ku drilled at the depocenter in western Taipei Basin. The high δ¹³C values (up to -17.0‰) and high C/N ratio (up to 14.9 and 13.0, respectively) indicate that this area underwent a period of relative aridity during MIS 2 and mid MIS 6. Another two periods of high and variable δ¹⁵N values (up to 15.5 and 13.5‰, respectively) in MIS 1 and MIS 7 represent different nutrient condition in the basin. In MIS 1, high δ¹⁵N variability along with increasing TOC may reflect an unstable trend of aquatic productivity related to the dynamic mixing ratios of seawater and fresh water. The high δ¹⁵N values observed in the sediments of MIS 7 could be explained by the employment of a ¹⁵N-enriched nitrate from denitrification as the main source of nitrogen for primary producers.