Holocene vegetational and coastal environmental changes from the Lago Crispim record in northeastern Pará State, eastern Amazonia

• Published in: Review of palaeobotany and palynology Vol. 114; no. 3; pp. 145 - 155
• Main Authors: Behling, Hermann, Lima da Costa, Marcondes
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2001
• Subjects: Amazon rain forest; coastal evolution; Holocene; mangrove; multi-element geochemistry; northern Brazil; palaeoecology; palaeofires; palynology; restinga; salt marsh; sea-level; multi-element geochemistry; palynology; coastal evolution; northern Brazil; Amazon rain forest; sea-level; mangrove; palaeofires; Holocene; palaeoecology; restinga; salt marsh
• ISSN: 0034-6667; 1879-0615
• DOI: 10.1016/S0034-6667(01)00044-6

Vegetational and coastal environmental changes have been interpreted from a 600 cm long and 7640 14C yr B.P. old sediment core from Lago Crispim located in the northeastern Pará State in northern Brazil. The radiocarbon dated sediment core was studied by multi-element geochemistry, pollen and charcoal analysis. Holocene Atlantic sea-level rise caused an elevation of local water table, which allowed the formation of organic deposits in a probably former inter-dune valley. Dense, diverse and tall Amazon rain forest, and some restinga (coastal vegetation) covered the study area at the beginning of the record at 7640 14C yr B.P. Mangrove vegetation developed along rivers close to the core site at that time. Subsequent decrease in less mangrove vegetation near the study site indicates a sea-level regression, beginning since around 7000 14C yr B.P. Lower sea-levels probably favoured the formation of a local Mauritia/Mauritiella palm swamp at 6620 14C yr B.P. Oscillations of higher and lower sea-level stands probably changed the size of the local palm swamp area several times between 6620 and 3630 14C yr B.P. Sea-level transgression at around 3630 14C yr B.P., caused marked coastal environmental changes: the development of mangroves near the site, the replacement of the local palm swamp by a Cyperaceae swamp, the substitution of the surrounding former Amazon rain forest and some restinga vegetation mainly by salt marshes. High amount carbonised particles suggest a strong human impact by burning on the coastal ecosystems during this late Holocene period. Highest concentrations of NaCl and also Ca, Mg and K in the upper sediment core indicate that the Atlantic was close during the late Holocene period. The core site, which is today 500 m from the coastline and only 1–2 m above modern sea-level, was apparently never reached by marine excursions during the Holocene. Less representation of mangrove since ca. 1840 14C yr B.P., may be related due to a slightly lower sea-level or to human impact in the study region. The modern shallow lake seems to be formed recently by road construction, forming an artificial dam.