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

Fornace, Kyrstin L.; Whitney, Bronwen S.; Galy, Valier; Hughen, Konrad A; Mayle, Francis E.

doi:10.1016/j.epsl.2016.01.007

Cited by 35 publications

(25 citation statements)

References 58 publications

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“…A progressive increase in regional effective precipitation best explains the evolution of the stable freshwater lake. Many paleolimnological and cave records from the Pantanal and elsewhere in the South American tropics bear witness to a late Holocene recovery from a drier climate (Fornace et al, 2016) that is consistent with our observations from Salina da Ponta.…”

Section: Hydrochemical and Climatic Changessupporting

confidence: 90%

Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

et al. 2017

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The objective of this research is to examine the history of lentic ecosystem salinity in the southern Pantanal wetlands (Brazil). The timing and controls on hydrochemical changes were inferred using sponge spicule and diatom paleoecology on a Holocene-aged sediment core from Nhecolândia, a lake district situated on a fossil lobe of the Taquari megafan. The oldest portion of the core contains Heterorotula fistula spicules, indicative of an ephemeral freshwater lake that existed until * 4.6 cal ka BP. Benthic diatoms of the genus Gomphonema and Eunotia appeared * 3.2 cal ka BP, indicating a shallow and dystrophic environment. A transition to a more permanent lake that hosted freshwater sponges (e.g., Corvoheteromeyenia spp.), and diatom assemblages (e.g., Cyclotella meneghiniana, Aulacoseira pantanalensis) endured until * 1.3 cal year BP; after this time, most sponges and planktic diatoms disappear from the sedimentary record. High abundances of Anomoeoneis sphaerophora and Craticula guaykuruorum in the latest Holocene reflect a transition to a hyperalkaline, saline lake environment. The results suggest that Nhecolândia's saline lakes may evolve from freshwater precursors due to local (biochemical) and regional (geo-climatic) controls on water availability, which has implications for patterns of biodiversity and ecosystems services in Pantanal.

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Section: Hydrochemical and Climatic Changessupporting

confidence: 90%

Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

et al. 2017

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“…The fact that the JAR record is characterized by wetter conditions during the Last Glacial than during the Holocene is in disagreement with interpretations of biological proxies at a nearby site1523. However, vegetation in the region may not have responded primarily to changes in precipitation.…”

Section: Discussionmentioning

confidence: 89%

“…1), at a location where hitherto no proxy records of similar resolution have been recovered. Fornace et al 15. recently published a stable isotopic record derived from leaf waxes in lake sediments from a shallow lake located at the Brazil-Bolivia border, a few hundred kilometers to the northwest from our site.…”

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confidence: 93%

A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene

Novello

Cruz

Vuille

et al. 2017

Sci Rep

156

104

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The exact extent, by which the hydrologic cycle in the Neotropics was affected by external forcing during the last deglaciation, remains poorly understood. Here we present a new paleo-rainfall reconstruction based on high-resolution speleothem δ18O records from the core region of the South American Monsoon System (SAMS), documenting the changing hydrological conditions over tropical South America (SA), in particular during abrupt millennial-scale events. This new record provides the best-resolved and most accurately constrained geochronology of any proxy from South America for this time period, spanning from the Last Glacial Maximum (LGM) to the mid-Holocene.

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“…Our data from the Late Pleistocene (48e19 ka) lobes of the Cuiab a megafan agree with environmental conditions interpreted from pollen records for regional lowlands. Stable carbon isotopes in bulk organic matter (d 13 C), carbon and hydrogen stable isotopes in leaf wax (d 13 C and dD) and pollen and diatom data from the Lagoa Gaiva sediments indicate an open vegetation landscape dominated by grasses and herbs during the last glacial period (41e20 ka) in the Pantanal wetland (Whitney et al, 2011;Metcalfe et al, 2014;Fornace et al, 2016). A similar scenario was interpreted through pollen and charcoal data from sediments of the Chaplin and Bella Vista Lakes in northeastern lowland Bolivia (southwestern Amazon Basin), which also suggest the expansion of dry forests and savannas during the last glacial period, especially during the LGM (Mayle et al, 2000;Burbridge et al, 2004).…”

Section: The Role Of Tectonic and Climate Controls On Fluvial Fan Evomentioning

confidence: 99%

Late Quaternary Cuiabá megafan, Brazilian Pantanal: Channel patterns and paleoenvironmental changes

Pupim

Assine

Sawakuchi

2017

Quaternary International

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The Brazilian Pantanal wetlands comprise some of the largest Quaternary megafans in South America. The origin of these megafans has been linked to climate changes during the Late Quaternary. This study focuses on the Cuiab a megafan, the second largest megafan of the Pantanal, which has not been studied from the perspective of its basic geomorphology, river channel patterns and sediment deposition ages. Analysis of the channel and floodplain morphology as well as optically stimulated luminescence dating enable us to establish the succession of events that built up the Cuiab a megafan since the last glacial period. Abandoned lobes indicate that a phase of fan aggradation occurred between 48 and 19 ka, with a network of distributary paleochannels suggesting that there was relatively low precipitation and reduced vegetation cover. Subsequently, abrupt changes in discharge and sediment supply triggered the channel incision of the upper fan valley, indicating a degradational phase after the Last Glacial Maximum (<19 ka). A new phase of fan aggradation began at the Early Holocene, when meandering and anabranching channels were constrained into the incised valley on the upper fan. In the distal part of the fan, the development of modern depositional lobes has been driven by numerous single-sinuous channels that shift laterally due to successive avulsions. Regional tectonic features suggest that modern Cuiab a lobes are in a subsiding area that provides accommodation space for sediment accumulation and prolonged flooding events. Changes in the channel patterns observed in the Cuiab a megafan are related to changes in the South American monsoon strength, which driven precipitation variation during the Late Quaternary. Periods of monsoon intensification and relatively high precipitation lead to channel incision, while periods of fan aggradation correlate to times of fewer oscillations. Our findings highlighted the diversity of fluvial styles in the Pantanal and its importance as a climate changes archives in the South American lowlands.

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

Abstract: Stable isotope analysis of leaf waxes in a sediment core from Laguna La Gaiba, a shallow

Cited by 35 publications

References 58 publications

Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene

Late Quaternary Cuiabá megafan, Brazilian Pantanal: Channel patterns and paleoenvironmental changes

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