Several Devonian black shale units in New York State display conspicuous basal discontinuities marked by accumulations of exhumed and reworked pyrite nodules, tubes, and fossil steinkerns. This coarse debris is overlain by, and/or interlayered with, black, laminated shale. The most important level is the Leicester Pyrite Member, which occurs along a regional unconformity flooring black shale deposits of the basal Genesee Formation; the detrital pyrite occurs in discontinuous lenses both on, and slightly above this surface. Basal Genesee beds (Geneseo Shale Member) record westward overlap of basinal, anoxic muds during a major marine transgression (Taghanic onlap). The reworked pyrite deposit is regionally diachronous, as indicated by conodont data and shingling of lenses with basal Genesee beds which are successively younger from east to west. Pyrite, chemically unstable in aerobic bottom settings, was exhumed and concentrated on the sea floor during brief erosion episodes in a normally anaerobic environment. Lenses contain istinctive diagenetic pyrite structures (e.g., fossil steinkerns, burrow tubes) derived from muds underlying the discontinuities. Erosional reworking of pyrite on the sea floor is shown by mechanical breakage of pyrite grains, reorientation of geopetal stalactitic pyrite and compactional features, plus alignment of pyritic tubes by bottom currents. General absence of carbonate allochems in lenses is believed to reflect dissolution of carbonate, following its exhumation. Episodic, deep storm-generated turbulence was probably important in exhuming and transporting pyrite. However, shoaling internal waves, impinging the sediment-starved basin margin slope, may also have been important in scouring the bottom. A model of internal wave erosion during the Taghanic transgression is presented herein; we feel that such erosion, concentrated at or near the base of the pycnocline during a period of relative sea level rise, offers a particularly good explanation for the observed juxtaposition of Geneseo and other similar black shale deposits on erosional discontinuities. The diachronous character of Leicester lenses and associated black Genesee muds above the unconformity suggests a transient rather than fixed basin axis allowing for progressive westward burial of the unconformity and assiciated remanié deposits by onlapping black muds. Older and younger occurrences of resedimented pyrite are briefly described from other Devonian basinal units and are shown to have formed in about the same manner as the Leicester. Reworked pyrite is believed to be common, although seldom recognized, in Phanerozoic sediment-starved basinal settings. Moreover, detrital pyrite, analogous to that described herein, probably awaits discovery in certain modern marine basins.