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Models dated by {sup 210}Pb; Modelos de fechado por {sup 210}Pb

Abstract

The {sup 210}Pb{sub ex} present in sediments, regardless of their origin, decays following the law of radioactive decay. If the rate of sediment accumulation and flow of {sup 210}Pb are constant and there are no redistribution processes of {sup 210}Pb{sub ex} in the sediment, a profile of {sup 210}Pb{sub ex} should be perfectly exponential. Although some of these conditions are not met in all cases and observed profiles are rarely found perfect exponentials, models dated by {sup 210}Pb described in this chapter allow to obtain valid dated. Anyway, the models described should be seen as tools of interpretation and the dates obtained as estimates to be corroborated by alternative observations. It is recommended to the reader to go deeper into the topics discussed in this chapter reading references and bibliography at the end. Throughout, the closed system hypothesis must be met. For dating of sediments implies that the radionuclide used is integrated into the matrix tested unaffected by redistribution processes. No cases of mixed sediments or showing evidence of mobility by diagenesis are addressed in this chapter, although we believe that in some circumstances estimates of the accumulation rates are provided but not of the age of formation. Starting with  More>>
Authors:
Sanchez-Cabeza, Joan-Albert; [1]  Ruiz-Fernandez, Ana Carolina [2] 
  1. Organismo Internacional de la Energia Atomica, Laboratorios del Medio Marino (Monaco)
  2. Universidad Nacional Autonoma de Mexico, Instituto de Ciencias del Mar y Limnologia (Mexico)
Publication Date:
Jul 01, 2012
Product Type:
Book
Resource Relation:
Other Information: 3 figs, 18 refs; Related Information: In: Sediment Radiochronology Using Coastal {sup 210P}b: Model, Validation and Applications (Spanish Edition)| 118 p.
Subject:
54 ENVIRONMENTAL SCIENCES; AGE ESTIMATION; DIAGENESIS; HYPOTHESIS; LEAD 210; NUCLEAR DECAY; SEDIMENTS; SURFACES
OSTI ID:
22030296
Research Organizations:
International Atomic Energy Agency, Radiometrics Laboratory, Marine Environmental Studies Laboratory (Monaco); United Nations Environment Program-Caribbean Regional Coordinating Unit (UNEP-CAR/RCU), Kingston (Jamaica)
Country of Origin:
IAEA
Language:
Spanish
Other Identifying Numbers:
Other: ISBN 978-92-0-325210-2; TRN: XA12N2099119001
Availability:
Also available on-line: http://www-pub.iaea.org/MTCD/Publications/PDF/P1538_S_web.pdf; Enquiries should be addressed to IAEA, Marketing and Sales Unit, Publishing Section, E-mail: sales.publications@iaea.org; Web site: http://www.iaea.org/books
Submitting Site:
INIS
Size:
page(s) 47-61
Announcement Date:
Jan 31, 2013

Citation Formats

Sanchez-Cabeza, Joan-Albert, and Ruiz-Fernandez, Ana Carolina. Models dated by {sup 210}Pb; Modelos de fechado por {sup 210}Pb. IAEA: N. p., 2012. Web.
Sanchez-Cabeza, Joan-Albert, & Ruiz-Fernandez, Ana Carolina. Models dated by {sup 210}Pb; Modelos de fechado por {sup 210}Pb. IAEA.
Sanchez-Cabeza, Joan-Albert, and Ruiz-Fernandez, Ana Carolina. 2012. "Models dated by {sup 210}Pb; Modelos de fechado por {sup 210}Pb." IAEA.
@misc{etde_22030296,
title = {Models dated by {sup 210}Pb; Modelos de fechado por {sup 210}Pb}
author = {Sanchez-Cabeza, Joan-Albert, and Ruiz-Fernandez, Ana Carolina}
abstractNote = {The {sup 210}Pb{sub ex} present in sediments, regardless of their origin, decays following the law of radioactive decay. If the rate of sediment accumulation and flow of {sup 210}Pb are constant and there are no redistribution processes of {sup 210}Pb{sub ex} in the sediment, a profile of {sup 210}Pb{sub ex} should be perfectly exponential. Although some of these conditions are not met in all cases and observed profiles are rarely found perfect exponentials, models dated by {sup 210}Pb described in this chapter allow to obtain valid dated. Anyway, the models described should be seen as tools of interpretation and the dates obtained as estimates to be corroborated by alternative observations. It is recommended to the reader to go deeper into the topics discussed in this chapter reading references and bibliography at the end. Throughout, the closed system hypothesis must be met. For dating of sediments implies that the radionuclide used is integrated into the matrix tested unaffected by redistribution processes. No cases of mixed sediments or showing evidence of mobility by diagenesis are addressed in this chapter, although we believe that in some circumstances estimates of the accumulation rates are provided but not of the age of formation. Starting with the first published use of {sup 210}Pb as a tool dating ice cores, different authors develop model conditions adapted to the dating of sediments. In this chapter we describe the most widely used models, which are based on assumptions about the flow of {sup 210}Pb{sub ex} the sediment surface, the rate of accumulation and concentration of initial{sup 210}Pb{sub ex} in surface sediments. The models describing nomenclatures have been different and even contradictory. To facilitate reading of the chapter we propose a nomenclature based on the fundamental assumptions of each model (not in implementation) and have homogenised the nomenclature used. While the model most commonly used for dating sediments is the CF (Constant Flux - Constant Flow), commonly known as CRS (Constant Rate of Supply), the model to use depends on the profile of {sup 210}Pb{sub ex} and the observed validity of the assumptions of each model in the study area. [Spanish] El {sup 210}Pb{sub ex} presente en los sedimentos, independientemente de su origen (ver Capitulo 2), decae siguiendo la ley de la desintegracion radiactiva. Si la tasa de acumulacion del sedimento y el flujo de {sup 210}Pb son constantes y no hay procesos de redistribucion del {sup 210}Pb{sub ex} en el sedimento, un perfil de {sup 210}Pb{sub ex} deberia ser perfectamente exponencial. Aunque algunas de estas condiciones no se cumplen en todos los casos y los perfiles observados no sean casi nunca perfectamente exponenciales, los modelos de fechado por {sup 210}Pb descritos en este capitulo permiten obtener fechados validos. En todo caso, los modelos descritos deben ser entendidos como herramientas de interpretacion y las fechas obtenidas como estimaciones que deben ser corroboradas mediante observaciones alternativas. Recomendamos al lector profundizar en los temas descritos en este capitulo leyendo las referencias y bibliografia al final del mismo. En todo fechado se debe cumplir la hipotesis de sistema cerrado. En el caso del fechado de sedimentos esto implica que el radionuclido utilizado quede integrado en la matriz analizada sin ser afectado por procesos de redistribucion. No abordamos en este capitulo los casos de sedimentos mezclados o que presenten evidencia de movilidad por diagenesis, si bien consideramos que en algunas circunstancias se pueden obtener estimaciones de las tasas de acumulacion pero no de las edades de formacion. A partir del primer uso publicado del {sup 210}Pb como herramienta de fechado de cores de hielo, diferentes autores desarrollan modelos adecuando las condiciones para el fechado de sedimentos. En este capitulo describimos los modelos mas ampliamente utilizados, los cuales se basan en hipotesis sobre el flujo de {sup 210}Pb{sub ex} a la superficie del sedimento, la tasa de de acumulacion y la concentracion inicial de {sup 210}Pb{sub ex} en los sedimentos superficiales. Los modelos que describimos han recibido nomenclaturas diferentes e incluso contradictorias. Para facilitar la lectura del capitulo proponemos una nomenclatura basada en las hipotesis fundamentales de cada modelo (no en su aplicacion) y hemos homogeneizado la nomenclatura utilizada. Si bien el modelo mas comunmente utilizado para fechar sedimentos es el CF (Constant Flux - Flujo Constante), comunmente conocido como CRS (Constant Rate of Supply), el modelo a utilizar depende del perfil de {sup 210}Pb{sub ex} observado y de la validez de las hipotesis de cada modelo en el area de estudio.}
place = {IAEA}
year = {2012}
month = {Jul}
}