The Beaufort Formation of Late Tertiary (probably late Miocene-early Pliocene) age occupies the western parts of the Arctic Islands bordering the Beaufort Sea. It extends from southern Banks Island on the south to Meighen Island on the north.

The best exposures of the Beaufort Formation, which are on northwestern Banks Island, can be lithologically subdivided into 2 or possibly 3 units separated by erosional unconformities. The lowest unit consists of a basal medium-fine cross-stratified sandstone followed by clay, woody peat, and a second clay zone. Each of these subunits is successively truncated by erosion on the east. The middle unit is characteristically light-colored gravel and coarse sand with minor amounts of uncompressed wood. This unit is overlain (in erosional contact) by darker, coarser gravels with abundant wood lenses. The two upper units correspond to the Beaufort Formation as defined on Prince Patrick Island, whereas the lower unit represents strata not known from that island. Elsewhere the strata can be as igned to either the upper or lower unit.

Mineralogically, the lowest unit is composed of about 70% quartz, 25% chert, and 5% others (shale chips predominantly). The middle unit consists of 60% quartz, 30-35% chert, and 5-10% others (predominantly shale). The upper unit consists of about 50% quartz, 35-40% chert, and 10-15% others (predominantly shale). The quartz is polycyclic whereas the chert and the shale are monocyclic. Paleocurrent data indicate that the straits between the islands developed in post-Beaufort time.

Megafossils belonging to Picea, Pinus, Larix, Alnus, 14 species of Bryophytes (identified by M. Kuc), and about 30 pollen and spore species have been identified. These indicate that at the time of deposition of the Beaufort, the climate was very similar to that of the Great Lake region today.

End_of_Article - Last_Page 2486------------