589 © Meteoritical Society, 2004. Printed in USA. Impact ejecta in upper Eocene deposits at Massignano, Italy

Abstract–Previous workers have shown that an impact ejecta layer at Massignano, Italy contains a positive Ir anomaly, flattened spheroids (pancake spherules), Ni-rich spinel crystals, and shocked quartz with multiple sets of planar deformation features. Because of sample sizes and work by different investigators, it was not clear if the shocked quartz is associated with the Ir anomaly and pancake spherules or if it belongs to a separate impact event. To address this problem, we carried out a high-resolution stratigraphic study of this ejecta layer. The ejecta layer was sampled continuously at 1 cm intervals in two adjacent columns. The carbonate was removed with dilute HCl, and the non-carbonate fraction was gently sieved. Pancake spherules were recovered from the 250–500 µm size fraction and counted. At the peak abundance, the number of pancake spherules in the 250–500 µm size fraction is about 6–7/g of sample. The pancake spherules removed from the 250–500 µm size fraction are mostly translucent to opaque pale green, but some have a grey color or dark opaque patches due to a coating of Ni- and Cr-rich spinel crystals. Energy-dispersive X-ray analysis and X-ray diffraction data indicate that the green spherules are composed of iron-rich smectite, probably nontronite. Black opaque spinel stringers (dark spinel-rich pancake spherules), usually <200 µm across, can be seen in a polished section of a block that includes the ejecta layer. None of the dar