UPPER DEVONIAN BRACHIOPOD AND CONODONT SEQUENCE THROUGH THE PUNCTATA ZONE EVENT (PZE) INTERVAL IN THE ALBERTA ROCKY MOUNTAINS, WESTERN CANADA

The punctata Zone event (PZE) is recorded by significant δ¹³C fluctuations of plus 2-5‰ culminating in minus 3-7‰ values prior to the Lower and Upper Kellwasser Extinctions (LKE and UKE) near the Frasnian-Famennian (F-F) boundary. Unlike the Kellwasser events, the PZE is not associated with significant perturbation of the benthic or pelagic biota outside of North America. A tropical North American faunal record spanning the PKE from western Alberta is presented here and is consistent with published records from eastern Laurussia. Temperature estimates interpreted from d18O from conodont apatites indicates that the late Givetian and early Frasnian were relatively cool and that the PZE event coincides with a warming trend that persisted until the first cooling pulse, or LKE, of the F-F extinction. In the Canadian Rocky Mountains of western Alberta, strata spanning the Early-Middle Frasnian transition and PKE are included in the Maligne, Cairn and lower Perdrix formations, and were deposited during Alberta Devonian depositional sequences 4 and 5.

Pre-PZE shelf faunas of the Early Frasnian Maligne Formation of sequence 4 are dominated by Desquamatia (Seratrypa), Schizophoria (S.), Eleutherokomma, Lateralatirostrum, Devonatrypa and Eostrophalosia. Coeval assemblages from shallow-water rimmed platform deposits of the Lower Cairn are dominated by Radiatrypa, Athyris, Allanella, Eleutherokomma, and Cyrtina. Middle Frasnian marine flooding and highstand deposits of sequence 5 spanning the PZE interval (punctata to Lower hassi Zones = M.N. Zones 5-7?) include basinal organic-rich shales of the lower Perdrix deposited on the drowned Maligne shelf, and rimmed platform carbonates of the Upper Cairn. In-situ low diversity deep-water assemblages of the Perdrix are dominated by Caryorhynchus and Plionoptycherhynchus. Carbonate debris flows derived from the Upper Cairn platform are interbedded with Lower Perdrix shales and yield more diverse assemblages that include species of Waioatrypa, Spinatrypa (S.), Pseudoatrypa, Devonatrypa, Gypidula, Nervostrophia, Devonoproductus, Eostrophalosia, Productella, Cyrtina, Conispirifer, Eleutherokomma, Elita, and Caryorhynchus. Only one genus (Allanella) is known to suffer extinction in carbonate platforms of central and western North America during the PKE.