Environmental Change in the Southwestern Coastal Plain of Taiwan since Late Pleistocene: Using Multiple Proxies of Sedimentary Organic Matter

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 mangroves and macrophytes were the main aquatic organic matter source in the Zai-kang area during MIS 1.

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