ALBERT

Description: The Ice Free Corridor has been invoked as a route for Pleistocene human and animal dispersals between eastern Beringia and more southerly areas of North America. Despite the significance of the corridor, there are limited data for when and how this corridor was used. Hypothetical uses of the corridor include: the first expansion of humans from Beringia into the Americas, northward postglacial expansions of fluted point technologies into Beringia, and continued use of the corridor as a contact route between the north and south. Here, we use radiocarbon dates and ancient mitochondrial DNA from late Pleistocene bison fossils to determine the chronology for when the corridor was open and viable for biotic dispersals. The corridor was closed after ∼23,000 until 13,400 calendar years ago (cal y BP), after which we find the first evidence, to our knowledge, that bison used this route to disperse from the south, and by 13,000 y from the north. Our chronology supports a habitable and traversable corridor by at least 13,000 cal y BP, just before the first appearance of Clovis technology in interior North America, and indicates that the corridor would not have been available for significantly earlier southward human dispersal. Following the opening of the corridor, multiple dispersals of human groups between Beringia and interior North America may have continued throughout the latest Pleistocene and early Holocene. Our results highlight the utility of phylogeographic analyses to test hypotheses about paleoecological history and the viability of dispersal routes over time.

Description: 〈div data-abstract-type="normal"〉〈p〉The Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 〈span〉10〈/span〉Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.〈/p〉〈/div〉

Description: The Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.

Description: Water grab samples collected ~weekly (total and routine parameters) and ~monthly (dissolved parameters) at the west bank of the Old Crow River mouth from May 28 – October 8, 2019 (Figure 1 of Staniszewska et al. 2022). The sampling location is 14 km downstream (7 km linear distance) of the Water Survey of Canada gauge station (09FC001; 67°35'20" N, 139°47'30" W), Yukon, Canada. Water samples were also collected from eight tributary creeks that drain into the Old Crow River, upstream and downstream of four large active retrogressive thaw slumps along the Old Crow River mainstem, as well as the thaw slump meltwater between 21 and 28 July 2019. All water samples were collected in precleaned polypropylene bottles (for routine parameters, trace elements, and nutrients) or Teflon-capped amber borosilicate glass bottles double-bagged in polypropylene (for mercury and methylmercury) following EPA Method 1669 (U.S. Environmental Protection Agency, 1996). Samples intended for total analysis were immediately acidified to 0.1% v/v with trace metal grade HNO3 (for trace elements and nutrients) and HCl (for mercury and methylmercury, to 0.2% and 0.4% v/v respectively) for the purpose of sample preservation. Samples were stored at 4 °C and transported to the laboratory, where samples intended for dissolved parameters were filtered through 0.45 µm HCl-washed cellulose nitrite filters and acidified. Field blanks were rinsed and filled at the bank of the river on a monthly basis. Duplicates were collected for the first month of weekly grab sampling events at the river mouth. River water samples were analyzed for a broad suite of parameters, including turbidity; pH; conductivity; alkalinity; total dissolved solids; total suspended solids; organic and inorganic carbon; major ions (Al, Ca, K, Mg, Na, SO4, Cl); stable hydrogen and oxygen isotopes; total and dissolved nitrogen and phosphorus species; 31 total and dissolved trace elements; and total and dissolved mercury and methylmercury by standard methods. Samples analyzed for total trace elements were processed by microwave digestion prior to analysis by inductively coupled plasma mass spectrometry (ICP-MS). This bundle contains four datasets: (1) Real-Time Provisional 2019 Hydrometric Data for Water Survey of Canada Station: OLD CROW RIVER NEAR THE MOUTH (09FC001) [YT], (2) Hydrochemistry data for Old Crow River mouth, collected between May and October, 2019, (3) Hydrochemistry data for tributary creeks to Old Crow River, collected between July 21 - 27, 2019, and (4) Hydrochemistry data for thaw slump upstream, downstream, and rill samples, collected between July 21 - 27, 2019.

Description: Real-Time Provisional 2019 Hydrometric Data for Water Survey of Canada Station: OLD CROW RIVER NEAR THE MOUTH (09FC001) [YT].

Description: Hydrochemistry data for Old Crow River mouth, collected between May and October, 2019

Description: Hydrochemistry data for tributary creeks to Old Crow River, collected between July 21 - 27, 2019

Description: Hydrochemistry data for thaw slump upstream, downstream, and rill samples, collected between July 21 - 27, 2019.