The stratigraphic, seddimentary pigment, loss—on—ignition, pollen, and radiocarbon data of a sedimentary record from Anangucocha, in the Ecuadorian Amazon, define three environmental episodes during the last 3100 yr. A swamp episode (<3100—1300 BP) was followed by regional flooding (1300—800 BP) and an open lake period (since 800 BP). Pollen data show that a Mauritia palm forest occupied the early blackwater swamp and was replaced by a riparian community dominated by Cecropia during the flooding episode. The pollen of Urticaceae—Moraceae taxa, especially Urtica, has increased in abundance since the flood. Past flooding was an important disturbance agent, which influenced the history of the plant community around Anangucocha. In the Amazon forest, such episodic flooding may be an important type of disturbance that promotes and maintains high species diversity. The Anangucocha record indicates that Amazonia experienced climatic fluctuation during the late Holocene.
SUMMARY 1. The stratigraphy, radiocarbon chronology, sedimentary pigment, and cation records of sediment cores from four lakes in the Ecuadorian rain forest show that regional flooding occurred from about 1300 to 800 ‘BP. Each core contains a stratum of alluvial clay, silt and sand overlain by lacustrine deposits of peat, gyttja or clayey gyttja. Radiocarbon dates show that the onset and termination of the alluvial event was synchronous across the sites. Short‐term, possibly regional, flooding occurred at each of the sites at least once since the major flood.
2. A core from Anangucocha, a black‐water lake, records the geoche‐ mical signature of white‐water incursion during this flooding interval. Sedimentary pigments show that aquatic production at Anañgucocha was low during the lotic interval but rose sharply and remained high within the modern lake period.
3. The Amazon's dynamic river system may have been an important force in promoting and maintaining high floral and faunal diversity.
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