Résumé
We conducted particle size analyses on 340 samples from Integrated Ocean Drilling Program Expedition 308 Sites U1324 (246 samples) and U1322 (94 samples) in the Ursa Basin (Gulf of Mexico) and found two characteristic lithologies: silty clay and clayey silt. Silty clays are composed of approximately 60% (+ or -10%) clay-sized particles by weight, approximately 40% silt-sized particles by weight, and <1% sandsized particles by weight. Clayey silts are generally composed of approximately 30% clay-sized particles by weight, 65%-70% silt-sized particles by weight, and 0%-5% sand-sized particles by weight. Site U1322 is dominated by silty clays with little particle size variation throughout the cored interval (0-235 meters below seafloor [mbsf]). At Site U1324, both lithologies occur where the lowermost section ( approximately 360-608 mbsf) is dominated by clayey silt and the uppermost section (0-360 mbsf) is dominated by silty clay.