DOI: 10.1016/j.palaeo.2014.03.034
论文题名: Magnetic fingerprint of the late Holocene inception of the Río de la Plata plume onto the southeast Brazilian shelf
作者: Mathias G.L. ; Nagai R.H. ; Trindade R.I.F. ; de Mahiques M.M.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2014
卷: 415 起始页码: 183
结束页码: 196
语种: 英语
英文关键词: Brazilian shelf
; Holocene
; Magnetic mineralogy
; Paleoceanography
; Río de la Plata
; South America
英文摘要: Measurement of changes in the assembly of magnetic particles in sediment records is useful both for paleoclimatic and paleoceanographic reconstructions and for assessing provenance and pathways of sediment transport. In this study we provide detailed rock magnetic analysis along with scanning electron microscopy (SEM), Ti/Ca ratio and particle size distribution of the decarbonated fraction of sediments to trace terrigenous source changes during the last 6. cal. kyr. BP in core 7610 collected on the SE Brazilian continental shelf. Magnetic mineralogy data indicate a gradual shift between two distinct sources of sediments: (1) dust from southern South America (Patagonia, central western Argentina and Puna-Altiplano plateau) and (2) sediments eroded from the weathered volcanics of Paraná Basin. These materials reached the continental margin off Argentina and Uruguay by different pathways and were transported northward by the Brazilian Coastal Current (BCC). The chronology of events related to the environmental record of core 7610 indicates that between 6 and 4.7. cal. kyr. BP dry conditions over continental South America resulted in enhanced eastward eolian transport of the Argentinean loess and a limited discharge of the RdlP river load into the Atlantic Ocean. At this time, the sedimentary magnetic fraction that reached the SE Brazilian shelf reflect predominantly loessic sources transported from the Pampean terraces to the Argentinean and Uruguay shelves and then distributed northward by the shelf current system. From 4.7 to 2. cal. kyr. BP the climate became gradually wetter over the continent and the contribution of oxidized phases from the weathered Paraná Basin (mainly from the basaltic and acidic volcanics) started to become important. This change in climate overlaps in time a with the late Holocene sea level fall recorded along the SE South American coast. Later, from 2 up to 0.9. cal. kyr. BP even wetter conditions were prevalent in S and SE South America, and the RdlP sedimentary load became the main source of sediments transported to the SE Brazilian shelf by the BCC. The magnetic record of core 7610 reported here together with other paleoenvironmental tracers (palynology, geochemistry and stable isotopes) thus indicates that the inception of the RdlP plume onto the SE Brazilian shelf started as early as 4.7. cal. kyr. BP and has been strengthened since then mostly due to changes in precipitation over South America and to a smaller extent by sea-level changes. © 2014 Elsevier B.V. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69176
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Departamento de Geofísica, Universidade de São Paulo, Rua do Matão, 1226, São Paulo, Brazil; Instituto de Oceanografia, Universidade de São Paulo, Praça do Oceanográfico, 191, São Paulo 05508-120, Brazil
Recommended Citation:
Mathias G.L.,Nagai R.H.,Trindade R.I.F.,et al. Magnetic fingerprint of the late Holocene inception of the Río de la Plata plume onto the southeast Brazilian shelf[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2014-01-01,415