FLUVIAL AND MARGINAL MARINE DEPOSITION OF THE YAHATINDA FORMATION, MIDDLE DEVONIAN, KAKWA LAKE PROVINCIAL PARK, EASTERN BRITISH COLUMBIA

Deposition of the Yahatinda Formation occurred during the Middle Devonian Watt Mountain Hiatus in western Alberta and eastern British Columbia. The Yahatinda disconformably overlies the Cambrian Ghost River Formation and is disconformably overlain by the Upper Givetian to Fransian Flume Formation. The fern spore Retusotriletes and fern tree Archaeopteris in mudstones and cross bedded sub-lithic arenites indicate a terrestrial fluvial environment. Fish fossils Onychodus and Holonema are shallow marine, but are rounded and broken indicating transport. The peritidal and fluvial mixed sand and gravel of the Yahatinda Formation were deposited in channels carved on the Watt Mountain unconformity surface, and ripple marks indicate a primary flow direction to the south. The source of sediment is the Gilwood Member of the Watt Mountain Formation in the Peace River Arch, northwestern Alberta.

A very fine grained cross bedded pure quartz arenite locally developed at the base of the Yahatinda occurs in some low laying karst channels and fractures in the Ghost River Formation. This sandstone contains fractures filled with secondary calcite that are not developed in the lithic arenites of the Yahatinda suggesting earlier deposition and cementation unrelated to the overlying strata.