Abstract
In an attempt to discriminate between organic matter sources and reconstruct further the paleoenvironment of the southwestern coastal plain of Taiwan, organic carbon and nitrogen content (C/N) ratios and isotope composition (δ13C and δ15N) are measured for sedimentary core samples collected from San-liao-wan, Zai-kang and Yihju in the southwestern coastal plain of Taiwan. Heavy δ13C values (up to -14.3‰) and high C/N ratios (average 9.3) with good correlation indicate that this area underwent a period of relative aridity from early Marine Isotopic Stage (MIS) 2 to the early MIS 1. In MIS 1, the δ13C and C/N ratio both vary initially before later steadying, indicating that the environment became progressively more stable, with C3 plants becoming dominant again. The Zai-kang core appears to have come from a shallow lagoon system that potentially preserved the record of δ15N from autochthonous primary producers. Regional organic source variation is revealed through the high δ15N values and constant C/N ratios in MIS 1 of the Zai-kang core. This may suggest that man- groves and macrophytes were the main aquatic organic matter source in the Zai-kang area during MIS 1.
Highlights
Isotopic analysis and carbon to nitrogen ratios of bulk sediment organic matter are widely used to discriminate various organic sources in order to reconstruct depositional environments, TAO, Vol 16, No 5, December 2005 or vegetation changes (Tenzer et al 1999; Schubert and Calvert 2001)
The southwestern coastal plain of Taiwan initially formed during the late Pleistocene
Δ13C and δ15N, and bulk abundances of total organic carbon (TOC) and total or ganic nitrogen (TON) along with their atomic carbon to nitrogen ratios (C/N) are used to diagnose detailed information about the paleo-environment afforded by three-core samples taken from San-liao-wan, Zaikang and Yihju
Summary
Isotopic analysis and carbon to nitrogen ratios of bulk sediment organic matter are widely used to discriminate various organic sources in order to reconstruct depositional environments, TAO, Vol 16, No 5, December 2005 or vegetation changes (Tenzer et al 1999; Schubert and Calvert 2001). Sedimentary sources vary and change rather often; core sediments record organic matter change and reflect regional environmental changes. The southwestern coastal plain of Taiwan initially formed during the late Pleistocene. It is covered by several hundred meters of alluvium captured by the gentle near-shore slope (Fig. 1). Swamps, lagoons and sand bars developed commonly along the shallow shore area with the rivers noted for their high sand content and frequent avulsion. This area received an abundant supply of eroded terrestrial sediments such as sandstone, shale, and mudstone from the Western Foothills to the east. Δ13C and δ15N , and bulk abundances of total organic carbon (TOC) and total or ganic nitrogen (TON) along with their atomic carbon to nitrogen ratios (C/N) are used to diagnose detailed information about the paleo-environment afforded by three-core samples taken from San-liao-wan, Zaikang and Yihju
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