Little Ice Age dryness in Northeast Brazil recorded by lacustrine sediments of lake Boqueirão explains discrepancies between 14C and 210Pb measurements

Abstract : Lake Boqueirão is located at 5°S latitude, on the Brazilian Atlantic coast, a region where the climate is directly influenced by the Intertropical Convergence Zone (ITCZ) displacements. Two cores were collected at different water depths based on a seismic survey. 210Pb were measured in the top 20 cm and 14C all along the profiles. The two methods indicated very different results concerning ages and sedimentation rates of the sediment. Lake level changes has been reconstructed using granulometry, Total Organic Carbon, C/N, 13C, 15N and Rock Eval (Hydrogen Index (HI), Oxygen Index (OI)). These proxies indicate large variations of the lake levels during the last 3000 cal yrs BP. Moreover, a prolonged dryness occurred in Lake Boqueirão since 570 cal yrs BP, till the last decades. This event provoked a drying of the lake at the two sampling sites. This drying can explains why the 210Pb method did not work in this lake probably due to an enrichment phenomenon of bare surfaces called " meteoric cap ". This dry phase corresponds to the Little Ice Age characterized by a cooler North Atlantic Ocean. These data indicate that the teleconnection pattern between tropical Atlantic, ENSO and Northeast Brazil rainfalls has changed in the past 3000 years.
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Submitted on : Thursday, July 11, 2013 - 11:10:09 AM
Last modification on : Tuesday, July 9, 2019 - 3:08:21 PM

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  • HAL Id : insu-00843366, version 1

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Bruno Turcq, Renata Zocatelli, R.L. Costa, Renato Campello Cordeiro, Ana Luiza Spadano Albuquerque, et al.. Little Ice Age dryness in Northeast Brazil recorded by lacustrine sediments of lake Boqueirão explains discrepancies between 14C and 210Pb measurements. 21th International Radiocarbon Conference, Jul 2012, Paris, France. ⟨insu-00843366⟩

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