Late Pleistocene and Recent Detrital Sedimentation in the Deep Parts of Northern Lake Tanganyika (East African Rift)

  1. P. Anadón,
  2. Li. Cabrera and
  3. K. Kelts
  1. F. Baltzer

Published Online: 14 APR 2009

DOI: 10.1002/9781444303919.ch8

Lacustrine Facies Analysis

Lacustrine Facies Analysis

How to Cite

Baltzer, F. (1991) Late Pleistocene and Recent Detrital Sedimentation in the Deep Parts of Northern Lake Tanganyika (East African Rift), in Lacustrine Facies Analysis (eds P. Anadón, Li. Cabrera and K. Kelts), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303919.ch8

Author Information

  1. URA 723 CNRS, Laboratoire de Pétrologie Sédimentaire et Paléontologie, Université Paris Sud, Bâtiment 504, 91405 Orsay, France

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 6 SEP 1991

ISBN Information

Print ISBN: 9780632031498

Online ISBN: 9781444303919

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Keywords:

  • Rusizi River-Lake Kivu origin;
  • Kullenberg piston corer;
  • Lower Grey Clays with diatomaceous laminae (LGCDL);
  • late Pleistocene and Holocene history of Lake Tanganyika;
  • Intermediate Detrital Formation, distinctive detrital episode;
  • Upper Detrital Formation, corresponding to dryer climatic episode;
  • Late Pleistocene and Recent detrital sedimentation in Lake Tanganyika

Summary

This study of the Recent sediments of northern Lake Tanganyika is based on high-resolution seismic profiling and 43 Kullenberg cores, made by Elf-Aquitaine (project Georift). In this part of the sub-basin, clastic sediments delivered via the N–S oriented Rusizi River and from lateral sources, are interbedded with laminated diatomaceous muds. Three episodes of detrital sedimentation have occurred since the late Pleistocene. Grain sizes, which range from clay to silt in most parts of the area, are coarser (sands, gravels, and mud balls) along a deep axis running N–S, parallel and close to the western shore of the lake. The predominant clay mineral, kaolinite, constitutes 50% of this mineral fraction.

The Lower Detrital Formation, documented in two cores situated on sublacustrine highs, includes the coarsest fractions, associated with smectite, abundant quartz, and feldspar. It is interpreted as a dry climatic episode older than 35000 yr BP. A gradual evolution from this low-stand formation to the present high-stand situation, is shown by an increase in the proportion of diatomaceous muds, i.e. a tendency towards pelagic conditions. This general trend is interrupted by two detrital episodes.

An intermediate episode (Intermediate Detrital Formation, c. 5000 yr BP), composed of light brown, beige clays and silts associated with coarser layers, indicates that deposition occurred in several distinct sequences relating to turbiditic events. The number of events decreases southward in the North Basin and this formation is not found in the South Basin, which suggests a southward direction of flow. Clay minerals (smectite) and coarse fraction minerals (quartz, plagioclase, orthoclase, siderite), coarse fraction mean size, and very high linear sedimentation rates sharply deviate from the general trend of lake sediments during this period. These data all suggest a Rusizi River–Lake Kivu origin, in agreement with the pollen data and the distribution of carbonates. Data confirm that Lake Tanganyika had already reached a high stand and suggest that the mineralogy of these deposits resulted from the influx of oxidized alluvium eroded from the Rusizi–Kivu basin, and sedimented into the strongly reducing waters of the hypolimnion.

The topmost, modern sedimentary unit (Upper Detrital Formation) covers most of the lake bottom and includes dark green muds, with a wide range of grain-sizes. Fine particles are ubiquitous, whereas the coarse fraction increases within the deep, western, lateral depression, confirming the importance of this depression as a main axis of sublacustrine transport. This formation, interpreted in terms of a drier climatic episode, begins with laminated diatomaceous muds that were largely replaced by detrital deposits by 2000 yr BP, but laminated diatomaceous muds have become more and more frequent in the latest deposits. Thus, the three major sedimentary units express changes in climate, provenance, and lake level.