Comparison of Ba/Ca and δ18OWATER as freshwater proxies: A multi-species core-top study on planktonic foraminifera from the vicinity of the Orinoco River mouth

被引：44

作者：

Bahr, Andre ^{[1
]}

Schoenfeld, Joachim ^{[2
]}

Hoffmann, Julia ^{[1
]}

Voigt, Silke ^{[1
]}

Aurahs, Ralf ^{[3
]}

Kucera, Michal ^{[3
]}

Floegel, Sascha ^{[2
]}

Jentzen, Anna ^{[2
]}

Gerdes, Axel ^{[1
]}

机构：

[1] Goethe Univ Frankfurt, Inst Geosci, D-60438 Frankfurt, Germany

[2] GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, D-24148 Kiel, Germany

[3] Univ Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen, Germany

来源：

EARTH AND PLANETARY SCIENCE LETTERS | 2013年 / 383卷

关键词：

foraminiferal Ba/Ca; delta O-18 of seawater; Ba desorption; Orinoco; Globigerinoides ruber; SEA-SURFACE TEMPERATURE; GULF-OF-MEXICO; GLOBIGERINOIDES-RUBER WHITE; TROPICAL NORTH-ATLANTIC; CARIBBEAN SEA; FLUVIAL GEOCHEMISTRY; DISSOLVED BARIUM; MIXING ZONE; AMAZON; EASTERN;

D O I：

10.1016/j.epsl.2013.09.036

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

Past river run-off is an important measure for the continental hydrological cycle and the assessment of freshwater input into the ocean. However, paleosalinity reconstructions applying different proxies in parallel often show offsets between the respective methods. Here, we compare the established foraminiferal Ba/Ca and delta O-18(WATER) salinity proxies for their capability to record the highly seasonal Orinoco freshwater plume in the eastern Caribbean. For this purpose we obtained a data set comprising Ba/Ca and delta O-18(WATER) determined on multiple species of planktonic foraminifera from core tops distributed around the Orinoco River mouth. Our findings indicate that interpretations based on either proxy could lead to different conclusions. In particular, Ba/Ca and delta O-18(WATER) diverge in their spatial distribution due to different governing factors. Apparently, the Orinoco freshwater plume is best tracked by Ba/Ca ratios of G. ruber (pink and sensu lato morphotypes), while delta O-18(WATER) based on the same. species is more related to the local precipitation-evaporation balance overprinting the riverine freshwater contribution. Other shallow dwelling species (G. sacculifer, O. universa) show a muted response to the freshwater discharge, most likely due to their ecological and habitat preferences. Extremely high Ba/Ca ratios recorded by G. ruber are attributed to Ba2+-desorption from suspended matter derived from the Orinoco. Samples taken most proximal to the freshwater source do not show pronounced Ba/Ca or delta O-18(WATER) anomalies. Here, the suspension loaded freshwater lid developing during maximum discharge suppresses foraminiferal populations. Both proxies are therefore biased towards dry season conditions at these sites, when surface salinity is only minimally reduced. (C) 2013 Elsevier B.V. All rights reserved.

引用

页码：45 / 57

页数：13

共 101 条

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