A LATE QUATERNARY MAGNETIC MINERAL RECORD FROM THE SEDIMENTS OF LAKE BOSUMTWI, GHANA
Distinct zones of differing magnetic mineralogies, grain-sizes and concentrations are readily identifiable down core and may relate to climatically driven changes in lithology. For example, between 94 255 cm an organic-rich sapropel lithology dates to approximately 3.1 8 14C ka. This lithologic zone is characterized by very high concentrations of moderate coercivity, pseudo single domain grains. This organic-rich sapropel represents a very humid period and lake level high stand (Talbot and Johannsen, EPSL 110, p. 23, 1992). Beneath 255 cm the sediment has extremely low magnetic concentrations of very coarse-grained (multidomain) magnetic minerals. However, there are three distinct zones at 255 280, 450 570 and 820 850 cm that have high concentrations of very fine-grained (single domain), extremely high coercivity minerals. Ongoing work is focused on determining if these pronounced magnetic mineral zones relate to the existing Bosumtwi lake-level curve and regional climate records.