A696 Goldschmidt Conference Abstracts 2005 The Earth's Weathering Engine Weathering process on tropical Influence of overstory vegetation on volcanics islands (Guadeloupe, long-term chemical weathering rates 1 2 3 Martinique and Réunion) A.W. SCHROTH , A.J. FRIEDLAND AND B.C BOSTICK by using U-series 1Dept. of Earth Sciences/ Environmental Studies Program, 6182 Steele Hall, Dartmouth College, Hanover, NH, S. RAD, J. GAILLARDET, P. LOUVAT, 03755, USA (
[email protected]) B. BOURDON AND C.J ALLEGRE 2Environmental Studies Program, Dartmouth College, IPGP, 4 place jussieu 75005 Paris, France Hanover NH, USA (
[email protected]) (
[email protected]) 3Dept. of Earth Sciences, Dartmouth College, Hanover NH, USA (
[email protected]) The volcanic islands of Guadeloupe, Martinique and Réunion, are particuarly interesting for the study of landscape The influence of overstory vegetation on long-term base erosion. Their lithology is andesitic (Martinique, Guadeloupe) cation depletion rates in soil is significant in the context of to basaltic (Réunion). They are located in a tropical climate global climate cycles, soil health and forest management, and with high temperatures (24°C to 28°C), high precipitation, neutralization of acid deposition. Because other variables that sharp relief and very dense vegetation. These characteristics influence chemical weathering in natural systems are often not favour high weathering rates with significant variations, over a controlled (i.e. parent material composition, elevation, land- short distance, from one basin to another. use history), studies that isolate overstory effects on chemical We have taken samples from main streams of Guadeloupe, weathering are limited, particularly on timescales that would Martinique and Réunion (dissolved phase, particles and sand) be evident in the pedogenic record.