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Continental shelf sediments along the northeast margin of North America contain a magnetofossil-rich interval that is coincident with the Paleocene-Eocene Thermal Maximum (PETM), an abrupt global warming event that occurred~ 56 Ma. The source of these magnetofossils is a combination of abundant, near-shore magnetotactic bacteria and unidentified iron-biomineralizing organisms. Previous studies using principal component analysis of high-resolution first-order reversal curves (FORC-PCA) show that there are at least three distinct populations of magnetofossils within these sediments: the biogenic soft, biogenic hard, and biogenic needle components. Transmission electron microscopy of magnetic extracts from these sediments confirms the presence of these components and documents the exceptional preservation and morphological disparity of the magnetofossils. FORC-PCA shows that the relative …