Ar-Ar ages of 58 individual hornblendes and micas picked from a discrete iceberg-rafted layer deposited ~1.2 Ma at IODP U1538. The layer was recovered 310.79–310.82 meters below sea floor in Hole U1538A-36X-3W. All hornblende and mica (mostly biotite) were handpicked from the 250-μm to 1-mm size fraction, with additional mica picked from the 63–250-μm size fraction. Hornblende, biotite and standards were irradiated at the Cd-lined in-core facility (CLICIT) at the Oregon State reactor. 40Ar/39Ar ages were obtained using single-step CO2 laser fusion at the Lamont Doherty Earth Observatory argon geochronology lab (AGES: Argon Geochronology for the Earth Sciences) to release argon, followed by cleanup with Zr-Ar getters heated at 2-amps. Extracted and cleaned gases were measured on a VG5400 noble gas mass spectrometer in peak hopping mode on an analogue multiplier, using the program Massspec. Nuclear interference corrections used values for OSU from Renne et al. (1998), and data were also corrected for background and mass discrimination using measured blanks and air pipettes. J values used to calculate ages were based on co-irradiated Fish Canyon sanidine standard (28.201±0.046 Ma; Kuiper et al. (2008), with decay constants from Min et al. (2000)).