POTENTIAL MEASURES OF INCREASING PALEOSTRESS CONDITIONS FOR MARINE BIOSPHERE IN GIVETIAN-FAMENNIAN SHALE-RICH SUCCESSIONS, NEW YORK AND OHIO

Herein, we summarize sequential lithologic and biostratinomic changes observed in the shale-dominated Givetian-Famennian succession of the northern Appalachian Basin that appear to record time-specific facies (TSFs) that are also time-sequential. Givetian mid-shelf-to-basin mudstones are characteristically gray to dark gray, often with concretions centered on coquinites with uncompressed molds of formerly aragonitic fossils. Aragonitic molluscan taxa are uniquely preserved as three-dimensional, recrystallized calcitic fossils in Lower Givetian neritic shales, but “fade” to composite molds in higher time-slice intervals. Middle and upper Frasnian, outer shelf-basin ramp facies are typically greenish-gray, bioturbated mudstone yielding sparse fossils with concretions containing flattened fossils. In the upper Frasnian Angola and Hanover members, beds of enigmatic micronodular carbonate resembling calcrete occur in this offshore TSF. Passing upward from Frasnian into Famennian, we see a change from deeply bioturbated to more shallowly burrowed and characteristically thinner-bedded, neritic facies. In middle and upper Famennian deposits, brachiopods and bryozoans suffer a sequential upward-degradation from robust calcite, through partial composite mold preservation, to composite molds comparable to aragonitic molluscan preservation. In the latest Famennian, enigmatic, offshore, red shale facies of the Bedford Formation may be a regional signal of the global Hangenberg Biocrisis in northern Ohio. Finally, proximality-related biofacies spectra become increasingly less varied, upward through the section, raising important questions as to whether these TSFs are “miners canaries” related to global biosphere decline, or merely responses to localized water mass controls.