Lithological and Palynological Evidence of late Quaternary Depositional Environments in the Subaqueous Yangtze Delta, China

Abstract

AMS 14C ages of post-glacial core sediments from the subaqueous Yangtze delta, along with sedimentary structures and distributions of grain size, pollen spores, and dinoflagellate cysts, show an estuarine depositional system from 13 to 8.4 cal ka BP and a deltaic system from 5.9 cal ka BP to the present. The estuarine system consists of intertidal to subtidal flat, estuarine, and estuarine-front facies, characterized by sand"mud couplets and a high sedimentation rate. The deltaic system includes nearshore shelf and prodelta mud featured by lower sedimentation rate, markedly fewer coastal wetland herbaceous pollens, and more dinoflagellate cysts. We explain the extremely high sedimentation rate during 9.2–8.4 cal ka BP at the study site as a result of rapid sea-level rise, high sediment load due to the unstable monsoonal climate, and subaqueous decrease of elevation from inner to outer estuary. A depositional hiatus occurred during 8.2–5.9 cal ka BP, the transition from estuarine to deltaic system, caused possibly by a shortage of sediment supply resulting from delta initiation in paleo-incised Yangtze valley and strong tidal or storm-related reworking in offshore areas. The subsequent development of deltaic system at the study site indicates accelerated progradation of Yangtze delta post-5.9 cal ka BP.

A new catalogue of tropical cyclones of the northern Bay of Bengal and the distribution and effects of selected landfalling events in Bangladesh

“…Even though India has a long civilization and history, its historical records are poorly preserved (Majumdar, ; Hoxie, ; Murthy, ). By contrast, official records of tropical cyclones in China go back to AD 816 (Louie and Liu, ) and geological records date back to 5900–8200 BP (Wang et al , ). In Australia, historical records of tropical cyclone are available from the 17th century onward, and geological records extend up to 5000–6000 BC (Nott, ) whereas on the coast of Florida, USA, geological records of hurricanes extend back to 5000 BC (Liu and Fearn, ).…”

Holocene environmental change inferred from multiple proxies in the mouth of Gomso Bay on the west coast of South Korea

“…Previous studies have described the paleoenvironmental changes in large river mouth areas, such as Mekong (Tamura et al, 2009), Red (Hori et al, 2004), and Changjiang Rivers (Hori et al, 2001a, 2001b; Wang et al, 2010; Song et al, 2013). These three areas share a similar Holocene sedimentary model (Hori et al, 2001a, 2001b, 2004; Tamura et al, 2009; Song et al, 2013; Feng et al, 2016), which may be divided into three stages (Fig.…”

“…Estuaries are among the most dynamic geomorphological units in marginal marine environments (Wang et al, 2010). These areas are very sensitive to changes in both sea level and climate (IPCC, 2014), but are also important for human activity.…”

“…However, most studies have focused on the mouths of very large rivers, such as the Mekong (Tamura et al, 2009), Red (Hori et al, 2004), and Changjiang Rivers (Hori et al, 2001a, 2001b; Wang et al, 2010; Song et al, 2013; Feng et al, 2016). Nearly all of these studies have reported that environmental changes during the Holocene were closely tied to sea-level changes.…”

Phytolith and diatom evidence for rice exploitation and environmental changes during the early mid-Holocene in the Yangtze Delta

“…Although many previous studies have reconstructed detailed environmental changes and climatic variability, especially in the southern parts of the delta (Liu et al, 1992;Zhang et al, 2004Zhang et al, , 2005Chen et al, 2005;Tao et al, 2006;Wang et al, 2010b;Wang et al, 2010cWang et al, , 2012Qin et al, 2011;Wang and Yang, 2013), reliable reconstruction is hampered by comparatively low temporal resolution in the middle and lower delta regions during the early mid-Holocene. Archaeological sites faithfully recorded the development of rice exploitation (Stanley and Chen, 1996;Atahan et al, 2007Atahan et al, , 2008Itzstein-Davey et al, 2007;Innes et al, 2009;Zong et al, 2011Zong et al, , 2012Innes et al, 2014;Long et al, 2014;Patalano et al, 2015); however, these records may lack the details necessary for the reconstruction of climate changes due to low temporal resolution, sedimental hiatuses, and extensive human influences.…”