The modern diatom spectra of Madagascar and diatom-inferred Late Quaternary climatic changes in northeastern and central Madagascar

Norman Evangelista Reyes, Fordham University

Abstract

A study was conducted to classify diatoms in modern sediment surface samples in freshwater sites into assemblages and to assess the historical changes in lake level changes and climatic conditions in Madagascar during the Late Quaternary. Analysis of taxonomic percentages of diatoms in recently deposited sediments from various sites shows that diatom communities in these sites can be grouped by means of cluster analysis into distinct assemblages, some of which show similarities to groupings found in East Africa. pH and conductivity appear to be important factors correlating with differences in diatom communities in these study sites. Trends in diatom assemblages in a sediment core taken from Lake Alaotra, supplemented by those in sediments of the paleolake Ampasambazimba, suggest that the late Pleistocene in northeastern Madagascar was arid, though aridity was probably not as constant or as severe as in many areas of eastern and northern Africa; the Holocene was a period of moderate but variable conditions, marked by a distinct dry episode ca 5000 yr B.P. and a drying trend toward the late Holocene. Changes in diatom assemblages in a sediment core from Lake Kavitaha in central Madagascar suggest changes in the surrounding environment during at least two periods in the late Holocene. These coincide with increases in charcoal influx and, around 700 yr B.P., with the intensification of agricultural activity in the area. ^

Subject Area

Ecology|Paleoecology|Limnology

Recommended Citation

Reyes, Norman Evangelista, "The modern diatom spectra of Madagascar and diatom-inferred Late Quaternary climatic changes in northeastern and central Madagascar" (1993). ETD Collection for Fordham University. AAI9313768.
http://fordham.bepress.com/dissertations/AAI9313768

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