Late Holocene palynology of a saline lake in the Pantanal of Nhecolândia, Brazil

ABSTRACT

This work presents the first description of a palynological assemblage preserved in sediments deposited in a saline lake (salina) in the Nhecolândia area of the Brazilian Pantanal. Pollen studies from salinas have been underappreciated due to inferred taphonomic issues related to elevated alkalinity. We have found a well-preserved assemblage that allowed the reconstruction of the history of local vegetation. Radiocarbon dating revealed a constant deposition since ∼3760 calibrated years before present (cal yrs BP), and pollen analyses suggested two main phases of vegetation and environmental development. From 3760 to 1510 cal yrs BP, the site was a swamp to shallow lake dominated by cattails (Typha domingensis) and Poaceae. From 1510 cal yrs BP to the present the herbaceous community is enriched with Cyperaceae and Bromeliaceae, and with tree taxa such as the Arecaceae (palm trees), evidencing the local development of a fringe vegetation. These two phases were interpreted as a change from drier to wetter settings, largely in agreement with regional lake and speleothem records, as well as pollen and carbon isotope studies from other locations in central South America during the latest Holocene. Given that salinas are non-floodable and pollen was found to be well preserved, we highlight the potential of palaeopalynology in these environments as a source of palaeoecological information for the Pantanal Basin.

KEYWORDS:

• pollen
• saline lake
• Quaternary
• Taquari megafan
• wetland
• environmental change

Acknowledgements

The authors thank Cátia Nunes da Cunha and Ana Costa Dantas, members of the evaluation commission; and Germano Guarim Neto, curator of the central Herbarium of UFMT. We thank Rafael V. Nunes for suggestions and helping with the translation of the manuscript, and Pollyne Rodrigues for generating the algae date. BFB received a Conselho Nacional de Pesquisa – CNPq grant. RLG acknowledges CAPES for a doctoral scholarship. The authors are grateful to the Fundação de Apoio à Pesquisa do Estado de São Paulo (FAPESP, grant number 2014/06889-2); to the Fundação de Apoio à Pesquisa do Estado de Mato Grosso (FAPEMAT, grant number 401809/2010-2) and to the Conselho Nacional de Desenvolvimento Científico e Tecnologico (CNPq, grant number 476020/2013-1) for financial support of our research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Fundação de Apoio à Pesquisa do Estado de São Paulo (FAPESP) [grant number 2014/06889-2]; the Fundação de Apoio à Pesquisa do Estado de Mato Grosso (FAPEMAT) [grant number 401809/2010-2]; and the Conselho Nacional de Desenvolvimento Científico e Tecnologico(CNPq) [grant number 476020/2013-1].

Notes on contributors

B.F. Becker

BÁRBARA FERNANDES BECKER is a biologist at the Universidade Federal de Mato Grosso (UFMT), and holds a master's degree in geosciences from the same institution. She currently works as a school science teacher, and as a collaborator of the palynology laboratory of Instituto de Geociências, UFMT, Cuiabá-MT, Brazil (PALMA). Her main interests are Quaternary palynology and environmental shifts during the Holocene in the Brazilian Pantanal.

S.A.F. da Silva-Caminha

SILANE APARECIDA FERREIRA DA SILVA-CAMINHA is a biologist at the Universidade Federal de Rondônia, Brazil. She holds a master's degree in botany from the National Institute of Amazonic Research – INPA. Her PhD topic was in ecology, and Silane studied at INPA and the Smithsonian Tropical Research Insitute. Currently she is a professor at the Faculdade de Geociências at the Universidade Federal de Mato Grosso (UFMT), and is the leader of the Mato Grosso Palynology and Amazonian Palynology research groups. Her main interests are in modern palynology and environmental shifts during the Paleogene/Neogene and Quaternary of Amazonia and the Brazilian Pantanal.

R.L. Guerreiro

MARIO LUIS ASSINE is a geologist at the Universidade Estadual Paulista Rio Claro (UNESP). He has a master's degree in regional geology from UNESP. Mario also holds a PhD in geosciences from the same institution. Currently he works as a professor in the Department of Geology at UNESP. His main interests are in the analysis of sedimentary basins such as the Araripe, Paraná, Campus and Santos depocentres, and the study of Quaternary geology, mainly the Pantanal Basin of Brazil.

E.J. de Oliveira

RENATO LADA GUERREIRO is a geographer at the Universidade Estadual do Paraná at Campo Mourão. He holds master's degrees in geography from the Universidade Estadual de Maringá, and in geosciences and environmental studies from UNESP. Renato has a PhD in geosciences and environmental studies from the latter institution. Currently he works as a professor at the Instituto Federal de Educação, Ciência e Tecnologia do Paraná. His main interests are palaeoenvironmental and palaeoclimatic shifts in the Quaternary of Pantanal, and analysis of multiproxies and landscape evolution.

C. D'Apolito

EDVALDO JOSÉ DE OLIVEIRA is a geologist at the Universidade Federal de Mato Grosso (UFMT). He has a master's degree in geosciences from the same institution, working on the Holocene palynology of the Pantanal Basin, Brazil. Edvaldo currently works as a geologist at the Public Ministry of the State of Mato Grosso, Brazil. This institution's main interests are environmental changes and the palynology of sedimentary basins.

M.L. Assine

CARLOS D'APOLITO is a postdoctoral researcher with the Smithsonian Tropical Research Institute, Panama, and is a visiting researcher at Universidade Federal de Mato Grosso (UFMT) in Cuiabá, Brazil. His main research interests are the evolution of vegetation and landscapes, palynology, palynostratigraphy and palaeobiogeography in neotropical areas during the Mesozoic and Cenozoic.