The vegetation response to MIS5 and MIS1 as revealed by pollen data from the Pearl River estuary, China

Abstract

The Pearl River delta (PRD) is situated on the southeastern coast of the Chinese mainland, facing the northern part of the South China Sea. Its estuary serves as the main sedimentary region for river discharge. The Quaternary sedimentary units consist primarily of two major sets of transgressive and regressive sequences. However, controversy exists regarding the chronology of the late Pleistocene marine transgression sequence. High-resolution records for the paleovegetation and paleoclimate of the late Quaternary upper and lower marine cycles are also lacking. In this study, a detailed analysis involving pollen, microfossils, and particle size has been carried out on a core from the Macau Sea area in the southwest of the Pearl River estuary. Chronostratigraphic models were based on accelerator mass spectrometry (AMS) ¹⁴C and optically stimulated luminescence (OSL) dating, combined with regional stratigraphic correlations. The reconstructed sediment facies for the late Pleistocene were mainly tidal flat, delta front, and pro-delta, corresponding to Marine Isotope Stage 5 (MIS5). The finding of mangrove Sonneratia pollen along with numerous tropical rain forest elements in the late Pleistocene sediments not only indicates a mud tidal flat environment in the PRD, but also reflects tropical climatic conditions. By comparing the pollen assemblages from the MIS5 and early part of the Holocene period (9.2–7.5 cal kyr BP) statistically, we obtained a consistent assemblage dominated by the same pollen taxa favoring warm and humid tropical conditions, which further confirmed the late (i.e. MIS5) age for the Pleistocene sequence. For the topmost samples representing the last 900 years, high percentages of Poaceae, Artemisia, Cyperaceae and fern spores, significantly different from those observed in samples from the early to mid-Holocene as well as the MIS5 interglacial sediments, indicated a strong anthropogenic impact on land cover.