THE ‘BLACK-SEAS’ OF THE DEVONIAN-CARBONIFEROUS BOUNDARY

The Devonian-Carboniferous boundary (DCB) is commonly associated with the Hangenberg extinction and black shale deposition in Europe (Baltica). Numerous studies attempted to correlate black shales from other parts of the world with the Hangenberg shale as a record of global anoxia –the cause of which remains debated. However, the prolonged time of anoxia and lack of prominent carbon cycle perturbation signal at the DCB are inconsistent with other more accepted anoxic events (e.g. Permian/Triassic anoxia, Cretaceous OAE’s).We examined new elemental and isotopic geochemical, stratigraphic, sedimentological, biostratigraphic and high precision ID-TIMS radiometric dating data from purported Hangenberg Event sections across the DCB of western Canada (Laurentia) to demonstrate that anoxic pulses and associated black shale deposition in Laurentian seas near the DCB are diachronous with the Baltican record. Thus, black shales of western Laurentia represent a record of a regional "Black Sea-like" restricted basin rather than a record of a global anoxia. During the latest Devonian to earliest Carboniferous, diachronous occurrence of “Black Sea-like” restricted basins around the globe left a record of an “apparent global Anoxia”.