Quaternary sedimentology east of Thunder Bay, Ontario; implications for five Paleoindian sites

A geoarchaeological investigation was north of Highway 11/17, 34km east \nof Thunder Bay, Ontario. Five archaeological sites (Mackenzie 1, Mackenzie 2, \nRLF, Woodpecker 1, and Woodpecker 2) and seven additional sediment \nexposures were examined for stratigraphic analysis to accompany the \narchaeological excavations. River-mouth sediments at 268m asl and a series of \ndeltas indicate that the study area was subaqueous while placement of the \nSuperior lobe prevented drainage to the Superior basin. This elevation is \nconsistent with Lake Beaver Bay, an ice-contact lake that received glacial \nmeltwater from the north (the Hudson Bay lobe) as well as the south (the \nSuperior lobe). This is demonstrated by southward and northward prograding \ndeltaic sequences within the study area. \nAs the Superior lobe made its final retreat, Lake Beaver Bay dissipated \ninto the Superior basin marking the beginning of the Minong phase, likely around \n9,900 14C yrs BP. Additional sequences representing river-mouth, beach \nshoreface, and deltaic depositional environments indicate that a series of \nshorelines within the study area represent subsequent Minong lake levels. The \nhighest, and likely oldest of these strandlines is an erosional feature at 256m asl, \nconsistent with wave-cut terraces previously identified in the Thunder Bay region. \nRelative lake level drops occurred, likely due to a combination of gradual \nerosion of the Nadoway Point sill and isostatic rebound of the recently \ndeglaciated land. Beach and river-mouth sequences representing subsequent \nshorelines are located at 249m, 243m, and 240m asl. Artifacts on each of these \nbeach terraces suggest they were occupied by Paleoindian groups.