SEQUENCE STRATIGRAPHY OF MIDDLE DEVONIAN (LATEST EIFELIAN-EARLY GIVETIAN) DEPOSITS IN SOUTWESTERN ONTARIO, NORTHERN OHIO AND NEW YORK: IMPLICATIONS INTERBASINAL CORRELATION

Middle Devonian (latest Eifelian-early Givetian) sediments of south-western Ontario and northern Ohio, deposited in the Chatham Sag and on the eastern and western flanks of the Findlay Arch (EFA & WFA) in the Appalachian and Michigan basins, show similar patterns of third- and fourth-order depositional sequence architecture; these can be correlated into the Skaneateles and Ludlowville formations of New York based on sequence stratigraphic pattern within a framework of conodont/goniatite evidence. In Ontario and WFA Ohio, a package of thin coral-rich limestones situated near the base of the hemiansatus conodont zone have been interpreted as deposits of an initial transgression (TST) of a 3rd-order depositional sequence, equivalent to the Stafford/Mottville members of the Skaneateles Fm. in New York. Where present, this coral-bearing limestone is everywhere overlain by an HST succession of grey to black mudrocks (Levanna Sh. [NY], Arkona Sh. [Ont.], Plum Brook Sh. [EFA], Silica Sh. [WFA]). Moreover, the Arkona, Plum Brook and Silica shale are sub-divisible into three small-scale (4th-order) argillaceous limestone-to-shale cycles that appear to correlate with the Delphi Station, Pompey and Butternut members of the Skaneateles Fm. in central NY. In all areas an uppermost, dark, leiorhynchid brachiopod-rich shale is sharply and unconformably overlain by a second coral-rich limestone (Centerfield [NY], Hungry Hollow [Ont.], lower Prout Ls. [EFA], lower Ten Mile Creek Fm. [WFA]) representing the TST of the next 3rd-order sequence. The overlying HST succession and component 4th-order sub-sequences of the Ludlowville Fm. in N.Y. are identified in the Widder and Ipperwash formations in Ontario. The upper Prout and Ten Mile Creek formations in Ohio represent the highly condensed HST of the Ludlowville Fm. These high-resolution correlations in two basins suggest allocyclic control and imply the need for revision of Middle Devonian sea-level curves. Further, these correlations provide a bridge into the adjacent Michigan Basin where stratigraphic correlations can now be extended into the Traverse Group. Sequence stratigraphic correlations allow for independent testing of faunal hypothesis between the two basins.