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No. de sistema: 000044561

LDR _ _ 00000nab^^2200000za^4500
008 _ _ 080129m20009999enk^r^p^^^^^^z0^^^a|eng^d
040 _ _ a| ECO
c| ECO
043 _ _ a| s-ck---
a| s------
044 _ _ a| enk
100 1 _ a| Veer, Ron van 'T
245 1 0 a| Climatic change during the Younger Dryas chron in northern South America
b| a test of the evidence
520 1 _ a| New AMS and palynological data are presented from the Colombian Andes to assess vegetational and climatic change during the Lateglacial–Holocene transition, with special emphasis on the Younger Dryas (YD) chronozone. The new evidence is compared and discussed with other Colombian cores and with data from other countries in the region. The Lateglacial climatic reversal in Colombia, known as the El Abra stadial, has an estimated lower boundary of 11,200 (conventional) and 10,900 (interpolated) 14C yr BP, respectively. Although the El Abra stadial is assumed to be the equivalent of the European YD, the present data suggest that the El Abra stadial is a biostratigraphical signal representing both the YD chronozone and the earliest Holocene (11,000–9000 14C yr BP). On the basis of new AMS dates and a re-evaluation of the pollen zones, we divided the Colombian El Abra biozone into two phases. From ca. 11,000 to ca. 10,500 14C yr BP there is a sharp increase of subparamo and paramo pollen, reflecting a relatively cool phase during the YD chronozone (zone Y1). After ca. 10,500 14C yr BP, a slight increase of arboreal pollen and the presence of Cactaceae (zone Z1) point toward a relatively milder but drier phase extending to ca. 9000 14C yr BP in the earliest Holocene.
520 1 _ a| Our conclusions add detail to the concept of astronomical forcing of contrasting rainfall changes in northern South America between 12,400 and 8800 14C yr BP. We propose an environmental drought during the El Abra biozone, with subsequent erosion of the sediments deposited during that period, as a major factor explaining the poor presence of YD evidence in northern South America. We conclude that at hydrologically sensitive sites without a clear lithological change around 11,000–9000 14C yr BP, a hiatus during the YD chronozone can only be detected if other cores are available with bracketed time control. We state that the start of the temperature decline in Central America and northern South America is related to the global YD cooling event. However, much work is still required to understand the duration and amplitude of the climatic reversal during the YD chronozone in this part of the globe.
650 _ 4 a| Palinología
650 _ 4 a| Cambio climático
651 _ 4 a| Colombia
651 _ 4 a| América del Sur
700 1 _ a| Islebe, Gerald A.
c| Doctor
e| coaut.
700 1 _ a| Hooghiemstra, Henry
e| coaut.
773 0 _
t| Quaternary Science Reviews
g| Vol. 19, no. 17-18 (December 2000), p. 1821-1835
x| 0277-3791
900 _ _ a| En hemeroteca, SIBE-Chetumal
902 _ _ a| EPV/DIMT / MM
904 _ _ a| Enero 2008
905 _ _ a| Artecosur
905 _ _ a| Biblioelectrónica
LNG eng
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*En hemeroteca, SIBE-Chetumal
Climatic change during the Younger Dryas chron in northern South America: a test of the evidence
Veer, Ron van 'T (autor)
Islebe, Gerald A. (autor)
Hooghiemstra, Henry (autor)
Contenido en: Quaternary Science Reviews. Vol. 19, no. 17-18 (December 2000), p. 1821-1835. ISSN: 0277-3791
No. de sistema: 44561
Tipo: Artículo
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Inglés

"New AMS and palynological data are presented from the Colombian Andes to assess vegetational and climatic change during the Lateglacial–Holocene transition, with special emphasis on the Younger Dryas (YD) chronozone. The new evidence is compared and discussed with other Colombian cores and with data from other countries in the region. The Lateglacial climatic reversal in Colombia, known as the El Abra stadial, has an estimated lower boundary of 11,200 (conventional) and 10,900 (interpolated) 14C yr BP, respectively. Although the El Abra stadial is assumed to be the equivalent of the European YD, the present data suggest that the El Abra stadial is a biostratigraphical signal representing both the YD chronozone and the earliest Holocene (11,000–9000 14C yr BP). On the basis of new AMS dates and a re-evaluation of the pollen zones, we divided the Colombian El Abra biozone into two phases. From ca. 11,000 to ca. 10,500 14C yr BP there is a sharp increase of subparamo and paramo pollen, reflecting a relatively cool phase during the YD chronozone (zone Y1). After ca. 10,500 14C yr BP, a slight increase of arboreal pollen and the presence of Cactaceae (zone Z1) point toward a relatively milder but drier phase extending to ca. 9000 14C yr BP in the earliest Holocene."

"Our conclusions add detail to the concept of astronomical forcing of contrasting rainfall changes in northern South America between 12,400 and 8800 14C yr BP. We propose an environmental drought during the El Abra biozone, with subsequent erosion of the sediments deposited during that period, as a major factor explaining the poor presence of YD evidence in northern South America. We conclude that at hydrologically sensitive sites without a clear lithological change around 11,000–9000 14C yr BP, a hiatus during the YD chronozone can only be detected if other cores are available with bracketed time control. We state that the start of the temperature decline in Central America and northern South America is related to the global YD cooling event. However, much work is still required to understand the duration and amplitude of the climatic reversal during the YD chronozone in this part of the globe."