Print this pagePreliminary Report on Modern Organism Traces from the Supralittoral to Sublittoral Zone in Kigoma Bay, Lake Tanganyika, Tanzania
Stephen T. Hasiotis1, David Kennedy2, Jonathan A. Todd3,
and Ellinor Michel3
1 University of Kansas, Lawrence, KS
2 University of Arizona, Tucson, AZ
3 The Natural History Museum, London, United Kingdom
Traces of modern organism-substrate relationships of Lake Tanganyika provide proxies from which soil moisture, water-table level, substrate consistency, shoreline position, water clarity, water depth, and total dissolved solids can be interpreted in the geologic record using ichnofossils in lacustrine deposits. Transects from supralittoral to profundal zones of rift lakes are paramount to interpret potential oil reservoirs and understand paleoecological settings of marine convergence.
The supralittoral to eulittoral zones are dominated by ant, termite, beetle, and vertebrate traces and plant-rooting patterns. Ants construct unlined simple to complex nests composed of chambers and galleries; termites reinforce chambers and galleries. Root depth and complexity decreases as depth to the water table decreases. Beetle burrows at the sediment-water-air interface and oligochaete grain disturbance in the vadose zone occur within 5 m of the shoreline. The number of tiers and maximum tiering depth of traces decreases toward the shoreline, resulting in one shallow tier due to high moisture and water level.
The littoral to sublittoral zones are dominated by traces of midge fly larvae, cichlid fishes, aquatic plant roots, small to large snails, bivalves, and microbial communities. Midge fly larvae construct thin vertical tubes that are very abundant. Cichlids produce small to large hemispherical pit and mound nests, sand-cone nests, snail-shell nests, shallow feeding pits, and surface feeding trails made by dorsal and pectoral fins. Bivalves make shallow burrows and short, deep trails. Snails create simple to complex trails. Ichnodiversity decreases toward the shoreline and decreases also within the sublittoral zone toward the profundal zone.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005