T28 Core Analysis of Lake Sediments (Posters)

Sunday, 22 October 2006
8:00 AM - 12:00 PM

PRELIMINARY PALEOECOLOGICAL RESULTS FROM THE LAKE MALAWI SCIENTIFIC DRILLING PROJECT

Paper number: T28-21
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Scientific drilling at Lake Malawi, (East Africa Rift Valley) in 2005 yielded a remarkable set of long cores which provide a high resolution record of environmental and climate change covering the last ~1.5Ma. The cores are highly fossiliferous, with excellently preserved invertebrates (ostracodes, insects, mollusks and sponges), disarticulated fish fossils, diatoms and other fossil algae and terrestrial plant fossils and charcoal. Our initial investigations include a low resolution (~10ka sampling interval) analysis of the longest core collected (380m), and an intermediate resolution (~300 years) analysis of the last ~150ka from the same site.

The two drill sites are currently located in very deep water (Sites 1 and 2 in 592m and 361m respectively), well below the oxicline of this meromictic lake (~100m). Modern, surface sediment analyses demonstrate that there is minimal transport and preservation of littoral/profundal benthic fossils into deep-water environments. Thus, the abundant benthic or littoral fossils found at various horizons in the Lake Malawi cores provide an unambiguous record of extraordinary lake level fluctuations of at least 590m. Ostracode assemblages are generally of low diversity and dominated by taxa indicative of the saline lake conditions prevailing during the low-stand/arid intervals. Charcoal records show large scale variability in fire activity in the region. Ongoing studies of the isotopic (C and N) composition of fish bones is being used to understand variations in food webs and their relationship to lake level fluctuations.