Postglacial vegetation and climate dynamics in the Seymour‐Belize Inlet Complex, central coastal British Columbia, Canada: palynological evidence from Tiny Lake
Abstract:A pollen-based study from Tiny Lake in the Seymour-Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a succession… Show more
“…1 and 6). About 90 km south of the study area, Seymour Inlet and northern Vancouver Island had a climate characterized as cold and dry prior to 13.9–13.8 cal ka BP (Lacourse, 2005; Stolze et al, 2007; Galloway et al, 2009), when a shift to a warmer climate is observed. These observations were based on palynological records recovered from lake cores.…”
Section: Discussionmentioning
confidence: 99%
“…(10) Woods Lake (Stolze et al, 2007). (11) Tiny Lake (Galloway et al, 2009). (12) Marion Lake (Mathewes and Heusser, 1981).…”
Descriptions of the Cordilleran Ice Sheet retreat after the last glacial maximum have included short-lived readvances occurring during the Older and Younger Dryas stadial periods and into the Holocene, but identification of these events has been largely limited to southwest and central British Columbia and northwest Washington State. We present evidence of a late Pleistocene readvance of Cordilleran ice occurring on the central coast of British Columbia on Calvert Island, between northern Vancouver Island and Haida Gwaii. Evidence is provided by sedimentological and paleoecological information contained in a sedimentary sequence combined with geomorphic mapping of glacial features in the region. Results indicate that a cold climate existed between 15.1 and 14.3 cal ka BP and that ice advanced to, and then retreated from, the western edge of the island between 14.2 and 13.8 cal ka BP. These data provide the first evidence of a major fluctuation in the retreating ice sheet margin in this region and suggest that a cold climate was a major factor in ice readvance. These data contribute to the understanding of past temperature, ice loading and crustal response, the nature of ice margin retreat, and the paleoenvironment of an understudied area of the Pacific Northwest.
“…1 and 6). About 90 km south of the study area, Seymour Inlet and northern Vancouver Island had a climate characterized as cold and dry prior to 13.9–13.8 cal ka BP (Lacourse, 2005; Stolze et al, 2007; Galloway et al, 2009), when a shift to a warmer climate is observed. These observations were based on palynological records recovered from lake cores.…”
Section: Discussionmentioning
confidence: 99%
“…(10) Woods Lake (Stolze et al, 2007). (11) Tiny Lake (Galloway et al, 2009). (12) Marion Lake (Mathewes and Heusser, 1981).…”
Descriptions of the Cordilleran Ice Sheet retreat after the last glacial maximum have included short-lived readvances occurring during the Older and Younger Dryas stadial periods and into the Holocene, but identification of these events has been largely limited to southwest and central British Columbia and northwest Washington State. We present evidence of a late Pleistocene readvance of Cordilleran ice occurring on the central coast of British Columbia on Calvert Island, between northern Vancouver Island and Haida Gwaii. Evidence is provided by sedimentological and paleoecological information contained in a sedimentary sequence combined with geomorphic mapping of glacial features in the region. Results indicate that a cold climate existed between 15.1 and 14.3 cal ka BP and that ice advanced to, and then retreated from, the western edge of the island between 14.2 and 13.8 cal ka BP. These data provide the first evidence of a major fluctuation in the retreating ice sheet margin in this region and suggest that a cold climate was a major factor in ice readvance. These data contribute to the understanding of past temperature, ice loading and crustal response, the nature of ice margin retreat, and the paleoenvironment of an understudied area of the Pacific Northwest.
“…1) is characterized by long, dry summers and relatively open Pseudotsuga menziesii –dominated forest. Figure 1.(color online) Map of Vancouver Island on the south coast of British Columbia, Canada, showing the location of Grant's Bog (star) and other paleoecological studies mentioned in the text: 1, Two Frog Lake and Tiny Lake (Galloway et al, 2007, 2009); 2, Bear Cove Bog (Hebda, 1983); 3, Misty Lake (Lacourse, 2005); 4, Port McNeill Bog (Lacourse and Davies, 2015); 5, Harris Lake Ridge Bog (Fitton, 2003) and Burman Pond (Mazzucchi, 2010); 6, Turtle Lake (Fitton, 2003); 7, Marion Lake (Mathewes, 1973); 8, Porphyry Lake (Brown and Hebda, 2003); 9, Roe Lake (Lucas and Lacourse, 2013); 10, Saanich Inlet (Pellatt et al, 2001); 11, Killebrew Lake (Leopold et al, 2016); 12, East Sooke Fen (Brown and Hebda, 2002). Top inset shows location in North America.…”
Peatland development and carbon accumulation on the Pacific coast of Canada have received little attention in paleoecological studies, despite wetlands being common landscape features. Here, we present a multi–proxy paleoenvironmental study of an ombrotrophic bog in coastal British Columbia. Following decreases in relative sea level, the wetland was isolated from marine waters by 13,300 cal yr BP. Peat composition, non-pollen palynomorph, and C and N analyses demonstrate terrestrialization from an oligotrophic lake to a marsh by 11,600 cal yr BP, followed by development of a poor fen, and then a drier ombrotrophic bog by 8700 cal yr BP. Maximum carbon accumulation occurred during the early Holocene fen stage, when seasonal differences in insolation were amplified. This highlights the importance of seasonality in constraining peatland carbon sequestration by enhancing productivity during summer and reducing decomposition during winter. Pollen analysis shows that Pinus contorta dominated regional forests by 14,000 cal yr BP. Warm and relatively dry summers in the early Holocene allowed Pseudotsuga menziesii to dominate lowland forests 11,200–7000 cal yr BP. Tsuga heterophylla and P. menziesii formed coniferous forest in the mid- and late Holocene. Tephra matching the mid-Holocene Glacier Peak–Dusty Creek assemblage provides evidence of its most northwesterly occurrence to date.
“…8.55±1.37 ka, CIDS10, and 11.5±2.0 ka, CIDS 12, Table S1) suggest that regionally cold and dry conditions (Galloway et al . ) instigated the development of large dune systems in coastal areas where sandy sediments became available. Dunes that formed west and south of the modern location of Cobble Beach (with remaining relict dune sand now perched on bedrock several m above sea level) provide good evidence that there were large stores of sediment to the west of this region, some of which probably constituted a broader expanse of Foggy Cove sediments (see Foggy Cove section above and Fig.…”
Section: Discussionmentioning
confidence: 99%
“…In addition, warmer, wetter climate conditions prevailed on the central coast of BC during this time period (Galloway et al . ; Eamer ), perhaps contributing to a reduction in the transport capacity for aeolian sediments and/or increased stabilization of aeolian dunes by vegetation. A small amount of detrital organic material found outcropping in the intertidal zone in the numbered beaches region (CIRC 12, Fig.…”
2018 (July): Late Quaternary landscape evolution in a region of stable postglacial relative sea levels, British Columbia central coast, Canada. Boreas, Vol. 47, pp. 738-753. https://doi.org/10.1111/bor.12297. ISSN 0300-9483.After retreat of the Cordilleran Ice Sheet (CIS) and subsequent glacio-isostatic adjustment of the central coast of British Columbia (BC), Canada, a complex coastline emerged as relative sea level rapidly reached equilibrium and maintained stability over the end of the Late Pleistocene and Holocene. This study provides a late Quaternary reconstruction of the landscape evolution of a geographically distinct location on the central BC coast, northwest Calvert Island, which experienced a re-advance of the CIS near the end of the Late Pleistocene and minimal subsequent relative sea-level change. Geomorphological observations from LiDAR imagery, sedimentological and palaeoecological evidence from exposures, cores and shovel pits, and a robust luminescence and 14 C-based chronology spanning the last 15 000 years are used to reconstruct the landscape of northwest Calvert Island following CIS retreat. A singlealiquot regenerative dose protocol that was developed specifically for luminescence dating of the sediments on Calvert Islandwas utilized in this study. Localized proglacial sedimentation was linked to the glacial re-advance experienced at the end of the Late Pleistocene. Extensive coastal reconfiguration (e.g. rapid shoreline progradation of >1 m a À1 ) occurred in the absence of extensive RSL change, which was the main driver of coastal change elsewhere along the BC coast. Changes in climate, small magnitude changes in RSL, and fire all probably played a role in isolated aeolian landform development and stabilization in the study area. An important contribution of this study is the documentation of the multi-disciplinary approach for reconstructing palaeogeography, using multiple geochronological methods, micro-and macro-sedimentology, the palaeoecology inferred from both macro and microfossils (e.g. diatoms and foraminifers), stratigraphy, field mapping and remote sensing. In addition, these findings inform our understanding of the drivers of coastal sedimentary processes, particularly in the temperate coastal rainforest region of BC, and the role that fire may play in those processes. Coastal palaeogeography studies in the region will become increasingly important as discoveries of Late Pleistocene human habitation along the coastal migration route continue to be documented.
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