Descriptions of drill cores and thin sections from lower Paleozoic strata, southeastern Baffin Island shelf, Nunavut

Abstract

Drill cores from the southeastern Baffin Island shelf offer rare insights into the lower Paleozoic bedrock geology that underlies the northern Baffin-Labrador Seaway Mesozoic to Cenozoic rift stratigraphy. Six seabed drill cores (Cruise 75-009 Phase V, Stations 4, 5, 8A, 8B and Cruise 77027, Stations 026A, and 028) were recovered from offshore Baffin Island by the Geological Survey of Canada during marine cruises in the 1970s. The lithology (sedimentology and paleontology) of the drill cores and their associated thin sections is analyzed to provide information on the depositional environments that existed in the Iapetus Ocean during the Middle to Upper Ordovician. The drill cores are predominantly composed of fine, lime mud, with evidence of bioturbation observed in four of the six cores. The drill cores exhibit varying degrees of dolomitization, with the drill core from 75-009, Phase V Station 4 being the most diagenetically altered. Disseminated pyrite is found throughout the drill cores and thin sections, and the cores from Stations 8A and 8B contain finely macerated organic matter dispersed in the matrix. Fossils identified in the drill cores and thin sections include bivalves, trilobites, crinoids, sponge spicules, gastropods, brachiopods, corals, cephalopods, dasycladacean green algae, ostracods, bryozoans, and radiolarians, as well as possible calcispheres. Undifferentiated echinoderm and shell fragments are also common throughout the strata. Initial interpretations based on observations from the drill cores and thin sections suggest depositional milieus ranging from shallow, photic zone environments to deeper, open marine settings.