Sr. Herwitz et al., ORIGIN OF BERMUDA CLAY-RICH QUATERNARY PALEOSOLS AND THEIR PALEOCLIMATIC SIGNIFICANCE, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D18), 1996, pp. 23389-23400
Red clayey paleosols that are chiefly the product of aerosolic dust de
position are interbedded in the Quaternary carbonate formations of the
Bermuda oceanic island system. These paleosols provide a basis for re
constructing Quaternary atmospheric circulation patterns in the northw
estern Atlantic. Geochemical analyses were performed on representative
paleosol samples to identify their parent dust source. Fine-grained f
ractions were analyzed by energy-dispersive X ray fluorescence to dete
rmine trace element (Zr, Y, La, Ti, and Nb) concentrations and to deri
ve geochemical signatures based on immobile element ratios. These rati
os were compared with geochemical signatures determined for three poss
ible sources of airborne dust: (1) Great Plains loess, (2) Mississippi
River Valley loess, and (3) Saharan dust. The Zr/Y and Zr/La ratios p
rovided the dearest distinction between the hypothesized dust sources.
The low ratios in the paleosol B horizons most closely resemble Sahar
an dust in the <2-mu m size class fraction. Contributions from the two
North American loessial source areas could. not be clearly detected.
Thus Bermuda paleosols have a predominantly Saharan aerosolic dust sig
nature. Saharan dust deposition on Bermuda during successive Quaternar
y glacial periods is consistent with patterns of general circulation m
odels, which indicate that during glacial maxima the northeast summer
trade winds were stronger than at present and reached latitudes higher
than 30 degrees N despite lower-than-present sea surface temperatures
in the North Atlantic.