Basinal black and dark-gray facies of the lower Genesee Formation (uppermost Givetian) contain distinctive accumulations of exhumed and resedimented pyrite nodules, tubes, and steinkerns. Pyritic alloclasts occur at 2 stratigraphic levels; each horizon marks an erosional discontinuity overlain directly by anaerobic or marginally dysaerobic, basinal sediments. The most important level is the Leicester pyrite member, marking the base of the formation, where pyrite occurs in starved traction-lenses on or immediately above a widespread unconformity marking a major transgression. This relict pyritic deposit is regionally time-transgressive, as indicated by conodont data and diachronous shingling of lenses with basal Genesee black muds. Similar, but younger, pyritic lenses occu at the level of a diastem associated with the western margin of the Lodi limestone bed near Seneca Lake. Pyrite, chemically unstable in aerobic bottom settings, was apparently exhumed, transported, and concentrated under euxinic conditions. Lenses contain distinctive diagenetic pyrite structures (e.g., steinkerns, burrow tubes) from muds underlying both discontinuities. Erosional transfer of pyrite onto the sea floor is shown by mechanical breakage of pyrite grains, reorientation of geopetal stalactitic pyrite, and compactional features, plus alignment of burrow tubes by bottom currents. General absence of carbonate allochems in lenses is believed to reflect dissolution of carbonate grains, particularly in the lens intergrain environment.

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