A Late Devonian Reef Tract on Northeastern Banks Island, N.W.T.

摘要: ABSTRACT The Upper Devonian Weatherall Formation, outcropping on northeastern Banks Island, N.W.T., contains a 200-ft-thick limestone unit here termed the Mercy Bay Member. member is Middle to Late Frasnian in age. Gyrfalcon Bluff has been chosen as type section. Member outcrops extreme portion of and many excellent exposures permit detailed paleogeographical paleoecological studies. numerous organic build-ups represents reef tract located marine-shelf environment an exogeosyncline situated between tectonic highland northwest stable craton southeast. main facies changes occur east-west direction. eastern part study area are narrow, linear bioherms trending north-south. They encased younger terrigenous clastic rocks. To west build-ups, which biohermal lower biostromal upper, more numerous. trend east-west. Penecontemporaneous interbiohermal strata consist dark, fine-grained argillaceous limestone. Organic western edge outcrop all consists corals tabular stromatoporoids. These interpreted biogenetic banks constructed quiet intermediate-energy zones (water depths than 30 ft). upper composed massive This rigid reefs high-energy zone (above feet). Successive sea-level rises allowed grow upward. Cessation growth was caused by influx sediment related seaward migration northern shorelines. tightly cemented, but frequent bitumen occurrences indicate that they were once oilbearing. probably subsurface west. End_Page 730------------------------