Abstract:AbstractA plant macrofossil record from the glacial Lake Hind basin is used to reconstruct early postglacial wetland plant succession and paleohydrology. Between >10.6 and 9.1 ka BP, there are four plant assemblage zones: (1) an early (>10.6 ka BP) zone dominated by Cyperaceae and aquatics; (2) a subsequent zone (~10.6-10.1 ka BP) with emergents (Menyanthes trifoliata,Potentilla palustris,Scirpus validus Show more
“…3 in Sun and Teller, 1997); deltas and fluvial deposits noted by letters A–P.Figure 3.Exposure along Souris River (modified from fig. 2 in Running et al, 2002), showing correlation between section described in this paper (B, right stratigraphic column) and that in Boyd (2003) (A, left stratigraphic column); note difference in vertical scales. Stratigraphic column A at the left shows units ”A” to “D” described by Boyd (2003, fig.…”
Section: Introductionsupporting
confidence: 58%
“…Figure 3 shows the exposed section, and provides a general description of the sequence discussed in this paper (Fig. 3B), with a correlation to the nearby section studied by Boyd (2003) and others (Fig. 3A).…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
confidence: 56%
“…The stratigraphy near the study site was described and interpreted by Boyd (2000a, 2003), Boyd et al (2003), Running et al (2002), Havholm and Running (2005), and Havholm et al (2003), with the eolian Holocene sequence being the focus of those studies. Figure 3 shows the exposed section, and provides a general description of the sequence discussed in this paper (Fig.…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
confidence: 96%
“…The modern Souris River has eroded into sediments deposited in the Glacial Lake Hind basin, and in places there are riverbank cuts that expose post-glacial lacustrine, fluvial, and eolian sediment, as well as peat. Some of these exposures have been studied, primarily to establish the Holocene eolian history and post-glacial paleoenvironmental conditions of the region (Boyd, 2000a, 2000b, 2003; Boyd et al, 2003; Running et al, 2002; Havholm et al, 2003; Havholm and Running, 2005). Other studies by Sun (Sun, 1996; Sun and Teller, 1997) and Matile and Keller (2004a) focussed on the overall geology of the Lake Hind basin.…”
Section: Location Of Study and Objectivesmentioning
confidence: 99%
“…3A). Unlike previous studies, our research focusses on the 2.8 m of silty sediment and organic deposits lying below the eolian sediments named units B to D by Boyd (2003; Fig. 3A).…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
Multi-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix) and deciduous trees (especially Populus and Quercus) covered the uplands from ~13 to 10 cal ka.
“…3 in Sun and Teller, 1997); deltas and fluvial deposits noted by letters A–P.Figure 3.Exposure along Souris River (modified from fig. 2 in Running et al, 2002), showing correlation between section described in this paper (B, right stratigraphic column) and that in Boyd (2003) (A, left stratigraphic column); note difference in vertical scales. Stratigraphic column A at the left shows units ”A” to “D” described by Boyd (2003, fig.…”
Section: Introductionsupporting
confidence: 58%
“…Figure 3 shows the exposed section, and provides a general description of the sequence discussed in this paper (Fig. 3B), with a correlation to the nearby section studied by Boyd (2003) and others (Fig. 3A).…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
confidence: 56%
“…The stratigraphy near the study site was described and interpreted by Boyd (2000a, 2003), Boyd et al (2003), Running et al (2002), Havholm and Running (2005), and Havholm et al (2003), with the eolian Holocene sequence being the focus of those studies. Figure 3 shows the exposed section, and provides a general description of the sequence discussed in this paper (Fig.…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
confidence: 96%
“…The modern Souris River has eroded into sediments deposited in the Glacial Lake Hind basin, and in places there are riverbank cuts that expose post-glacial lacustrine, fluvial, and eolian sediment, as well as peat. Some of these exposures have been studied, primarily to establish the Holocene eolian history and post-glacial paleoenvironmental conditions of the region (Boyd, 2000a, 2000b, 2003; Boyd et al, 2003; Running et al, 2002; Havholm et al, 2003; Havholm and Running, 2005). Other studies by Sun (Sun, 1996; Sun and Teller, 1997) and Matile and Keller (2004a) focussed on the overall geology of the Lake Hind basin.…”
Section: Location Of Study and Objectivesmentioning
confidence: 99%
“…3A). Unlike previous studies, our research focusses on the 2.8 m of silty sediment and organic deposits lying below the eolian sediments named units B to D by Boyd (2003; Fig. 3A).…”
Section: Stratigraphy Of the Flintstone Hills Sequencementioning
Multi-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix) and deciduous trees (especially Populus and Quercus) covered the uplands from ~13 to 10 cal ka.
Lake Agassiz was ponded on the northward-sloping surface of the Hudson Bay and Arctic Ocean basins, as the Laurentide Ice Sheet retreated. The level of Lake Agassiz abruptly fell ~ 12.9 cal (11 14C) ka BP, exposing the lake floor over a large region for > 1000 yr. The routing of overflow during this (Moorhead low-water) period is uncertain, and there is evidence on the continent and in ocean basins for both an easterly route through the Great Lakes–St. Lawrence to the North Atlantic and for a northwesterly route through the Clearwater–Athabasca–Mackenzie system to the Arctic Ocean. The Moorhead low water phase coincides with the Younger Dryas cooling, and a cause–effect relationship has been proposed by attributing a change in ocean thermohaline circulation to the re-routing of Lake Agassiz freshwaters from the Gulf of Mexico to more northern oceans. Paleoclimatic interpretations from ecosystems in lake sediments in the region, and a simple calculation of the paleohydrological budget of Lake Agassiz, indicate that the climate remained wet and cool throughout the YD in this region, and was not warm nor dry enough to allow evaporative loss to offset the influx of meltwater and precipitation; thus, the Moorhead phase resulted from changes in the outlet that carried overflow.
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