Sedimentary facies and Holocene progradation rates of the Changjiang (Yangtze) delta, China

Citation
K. Hori et al., Sedimentary facies and Holocene progradation rates of the Changjiang (Yangtze) delta, China, GEOMORPHOLO, 41(2-3), 2001, pp. 233-248
Citations number
58
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOMORPHOLOGY
ISSN journal
0169-555X → ACNP
Volume
41
Issue
2-3
Year of publication
2001
Pages
233 - 248
Database
ISI
SICI code
0169-555X(20011115)41:2-3<233:SFAHPR>2.0.ZU;2-0
Abstract
The Changjiang (Yangtze) River, one of the largest rivers in the world, has formed a broad tide-dominated delta at its mouth during the Holocene sea-l evel highstand. Three boreholes (CM97, JS98, and HQ98) were obtained from t he Changjiang delta plain in 1997-1998 to clarify the characteristics of ti de-dominated delta sediments and architecture. Based on sediment compositio n and texture, and faunal content, core sediments were divided into six dep ositional units. In ascending order, they were interpreted as tidal sand ri dge, prodelta, delta-front, subtidal to lower intertidal flat, upper intert idal flat, and surface soil deposits. The deltaic sequence from the prodelt a deposits to the delta front deposits showed an upward-coarsening successi on, overlain by an upward-fining succession from the uppermost part of the delta front deposits to the surface soil. Thinly interlaminated to thinly i nterbedded sand and mud (sand-mud couplets), and bidirectional cross lamina tions in these deposits show that tide is the key factor affecting the form ation of Changjiang deltaic facies. Sediment facies and their succession co mbined with AMS C-14 dating revealed that isochron lines cross unit boundar ies clearly, and delta progradation has occurred since about 6000 to 7000 y ears BP, when the rising sea level neared or reached its present position. The average progradation rate of the delta front was approximately 50 km/ky ear over the last 5000 years. The progradation rate, however, increased abr uptly ca. 2000 years BP, going from 38 to 80 km/kyear. The possible causes for this active progradation could have been an increase in sediment produc tion in the drainage basin due to widespread human interference and/or decr ease in deposition in the middle reaches related to the channel stability c aused by human activity and climatic cooling after the mid-Holocene. (C) 20 01 Elsevier Science B.V. All rights reserved.