Hydrology and climatology at Laguna La Gaiba, lowland Bolivia: complex responses to climatic forcings over the last 25 000 years

Abstract

Diatom, geochemical and isotopic data provide a record of environmental change in Laguna La Gaiba, lowland Bolivia, over the last ca. 25,000 years. High-resolution diatom analysis around the last glacial -interglacial transition provides new insights into this period of change. The full and late glacial lake was generally quite shallow, but with evidence of periodic flooding. At about 13,100 cal a BP, just prior to the start of the Younger Dryas chronozone, the diatoms indicate shallower water conditions, but there is a marked change at about 12,200 cal a BP indicating the onset of a period of high variability, with rising water levels punctuated by periodic drying. From ca. 11,800 to 10,000 cal a BP stable, deeper water conditions persisted. There is clear evidence for drying in the early to mid Holocene, but not as pronounced as that reported from elsewhere in the southern hemisphere tropics of South America. This was followed by the onset of wetter conditions in the late Holocene consistent with insolation forcing. Conditions very similar to present were 2 established about 2,100 cal a BP. A complex response to both insolation forcing and millennial scale events originating in the North Atlantic is noted.

Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest

“…This lake has yielded long-term palaeoclimate records, inferred from reconstructed lake-level changes [19][20][21] and pollen-based vegetation reconstructions [22,23]. These records indicate that eastern Chiquitanía and the Pantanal have rstb.royalsocietypublishing.org Phil.…”

“…The LLG record extends beyond 40 000 years BP and demonstrates large-scale landscape rearrangement and catchment change in the western Pantanal at the end of the Pleistocene [21,22]. Our analysis focuses on the last 12 000 years; a period defined by landscape stability, the establishment of modern lake conditions and the spread of SDTF in eastern Chiquitanía [22,23].…”

Impact of pre-Columbian “geoglyph” builders on Amazonian forests

“…Charcoal was extracted using a macroscopic sieving method (57) and divided into size classes to distinguish local (>250 μm) from extralocal (125-250 μm) burning signals. Stable carbon isotope analysis of SOM was conducted at JS1 (every 10 cm) and JS3 (every 10 cm, then every 20 cm below 0.4 m below surface) using standard procedures (58). Detailed information for the methodologies used in this study is provided in SI Methods.…”

Late Quaternary environmental change in the interior South American tropics: new insight from leaf wax stable isotopes

“…Available pollen records from several sites in the southern Amazon Basin point to drier conditions during the last glacial period (Mayle et al 2000;Burbridge et al, 2004), suggesting a disconnect between the interior tropics and other regions. Several recent studies have focused on reconstructing hydrologic conditions in the Pantanal, a large wetland expanse primarily located in the Mato Grosso do Sul region of Brazil and roughly equidistant between the well-studied Central Andes and southern Brazil regions (Metcalfe et al, 2014;Whitney et al, 2011;Whitney and Mayle, 2012;McGlue et al, 2012). Evidence from pollen, diatoms and other biological proxies in a continuous ~45,000-year sediment record from Laguna La Gaiba (LLG) suggest drier and cooler conditions in the Pantanal during the last glacial period (Metcalfe et al, 2014;Whitney et al, 2011).…”

“…Several recent studies have focused on reconstructing hydrologic conditions in the Pantanal, a large wetland expanse primarily located in the Mato Grosso do Sul region of Brazil and roughly equidistant between the well-studied Central Andes and southern Brazil regions (Metcalfe et al, 2014;Whitney et al, 2011;Whitney and Mayle, 2012;McGlue et al, 2012). Evidence from pollen, diatoms and other biological proxies in a continuous ~45,000-year sediment record from Laguna La Gaiba (LLG) suggest drier and cooler conditions in the Pantanal during the last glacial period (Metcalfe et al, 2014;Whitney et al, 2011). During the Holocene, hydrologic patterns in the Pantanal appear to be consistent with other SASM records, with a relatively dry early/mid-Holocene followed by wetter conditions in the late Holocene (Metcalfe et al, 2014;Whitney et al, 2011;Whitney and Mayle, 2012;McGlue et al, 2012).…”