Paleo-environmental evolution as revealed by analysis of organic carbon and nitrogen: A case of coastal Taipei Basin in Northern Taiwan

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 (δ 13 C and δ 15 N) are measured for sediment samples collected from core Wu-ku drilled at the depocenter in western Taipei Basin. The high δ 13 C 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 δ 15 N 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 δ 15 N 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 δ15 N values observed in the sediments of MIS 7 could be explained by the employment of a 15 N-enriched nitrate from denitrification as the main source of nitrogen for primary producers.

Climatic changes since the last deglaciation inferred from a lacustrine sedimentary sequence in the eastern Nanling Mountains, south China

“…Stable isotope ratios of organic carbon are affected by a number of factors (Stuiver, 1975; Hakansson, 1985; Ku et al , 2007) such as [CO 2 ]aq, temperature and precipitation. Besides the primary producer (i.e.…”

“…Each of these sources is characterised by different isotopic values (O'Leary, 1988). Primary producers and macrophytes have wide‐ranging δ 13 C org values from −27‰ to −17‰ (Ku et al , 2007). On the other hand, the source of terrestrial plants is dominated by three distinct vegetation groups – the C3, C4 and CAM plants – which employ different photosynthetic pathways and produce different δ 13 C org values.…”

Bulk organic carbon isotopic record of lacustrine sediments in Dahu Swamp, eastern Nanling Mountains in South China: Implication for catchment environmental and climatic changes in the last 16,000 years

“…Each of these sources is characterized by different carbon isotopic values (O'Leary, 1988). Primary producers and macrophytes have wideranging d 13 C org values from À27.0 to À17.0‰ (Ku et al, 2007). A previous study (Lücke et al, 2003) has pointed out that in the mid-latitudes of the Northern Hemisphere organic carbon derived from land plants and aquatic macrophytes is characterized by d 13 C org values in general higher than À28.0‰ (e.g., Osmond et al, 1981;LaZerte, 1983;Meyers and Ishiwatari, 1995) while lacustrine algae, respectively, lacustrine sediments normally show values below À25.0‰.…”

Humification degrees of a lacustrine sedimentary sequence as an indicator of past climatic changes in the last c. 49 000 years in South China

“…Each of these sources is characterized by different isotopic values (O'Leary 1988). Primary producers and macrophytes have wide‐ranging δ 13 C org values from −27‰ to −17‰ (Ku et al 2007). On the other hand, the sources of terrestrial plants are dominated by three distinct vegetation groups, namely the C3, C4 and CAM plants, which employ different photosynthetic pathways and produce different δ 13 C org values.…”

“…3). The organic carbon isotopic ratio of lacustrine sediments is affected by a number of factors (Stuiver 1975;Hakansson 1985;Ku et al 2007). Besides the primary producer (i.e.…”