High-resolution paleoclimate reconstruction of the last 9000 years based on speleothem isotope records from northeastern Venezuela

• Main Author: Martinez Medina, Nathalie Melissa
• Other Authors: Cruz, Framcisco William
• Format: Master Thesis
• Language: English
• Published: Biblioteca Digital de Teses e Dissertações da USP 2022
• Subjects: América do Sul; Venezuela; Paleoclima; Isótopos estáveis; Zona de Convergência Inter-tropical; Holoceno; Espeleotemas; Ciclos Bond; Bacia de Cariaco; Caribe; Stable isotopes; Speleothems; South America; Paleoclimate; Bond cycles; Cariaco Basin; Caribbean; Holocene; Inter-tropical Convergence Zone; Alta; Nordeste; North Atlantic
• Online Access: https://www.teses.usp.br/teses/disponiveis/44/44142/tde-10082022-082214/; https://doi.org/10.11606/D.44.2022.tde-10082022-082214

Few high-resolution paleoclimate proxy records exist in the region located under the direct influence of the Inter-tropical Convergence Zone (ITCZ) in South America (SA); most of them retrieved from the Cariaco Basin (CB) off the coast of Venezuela. Here we present new high-resolution 18O and 13C records of speleothems collected in caves in the region adjacent to the CB in Venezuela, covering the Mid and Late Holocene. We document previously undetected multidecadal- to secular-scale climate variability in the core region of the ITCZ, which is being compared to other high-resolution records from the North Atlantic (NA), Caribbean and southern tropical South America. We show that the northeastern Venezuelan Holocene hydroclimate variability and the input of nutrients, productivity and oxygen demand in the CB has primary (but not exclusively) responded to NA climate (Bond cycles). However, the magnitude of those events and the background insolation conditions might have been the main determinants. Increased Northern Hemisphere (NH) insolation during the Mid-Holocene likely led to mostly in-phase relation between Venezuela and eastern Caribbean records (i.e. wet conditions occurred between 8.1-6.5 ka despite coinciding with Bond 5, due to the enhanced NH insolation and northward position of the ITCZ, whereas dry conditions were observed during the strongest of the Bond Cycles (4) around 5.5 ka). In addition, the comparison between the speleothem record of this study and other ones suggest that ITCZ stayed between Venezuela and Barbados as a narrower band during weaker and shorter events such as the Bond 3 with drying conditions observed to the north in Cuba and to the south in Peru. Our NE Venezuela record from Caripe Cave considerable differs from the Cariaco Basin Ti record during the last 2.3 ka. Pointing to non-previously reported relations to Caribbean and southern hemisphere tropical high-resolution records. During this period an out-phase relation is observed between Venezuela and Caribbean records and rather ...