In Search of Antarctica's Last Vegetation Refugium Within the McMurdo Dry Valleys
The McMurdo Dry Valleys, a hyper-arid cold polar desert located within the Transantarctic Mountains was once covered by vegetation. An in depth study of surface samples of various Neogene age, acquired throughout the Valleys, provide insight to the location of one of Antarctica’s last vegetation ref...
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LSU Digital Commons
2017
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| Online Access: | https://digitalcommons.lsu.edu/gradschool_theses/4468 https://doi.org/10.31390/gradschool_theses.4468 https://digitalcommons.lsu.edu/context/gradschool_theses/article/5469/viewcontent/Rau_Thesis.pdf |
| Summary: | The McMurdo Dry Valleys, a hyper-arid cold polar desert located within the Transantarctic Mountains was once covered by vegetation. An in depth study of surface samples of various Neogene age, acquired throughout the Valleys, provide insight to the location of one of Antarctica’s last vegetation refugia. Boston University’s Antarctic Research Group has collected 82 surface samples from paleo lake sediments on 14 expeditions spanning 22 years in the McMurdo Dry Valleys. The ages of the samples are still not fully constrained, but 8 regions where samples were collected have been interpreted to range between 16.95 ± 0.17 to 4 Ma old (Marchant, pers. comm.). Results show the palynomorph assemblage diversity is low with a terrestrial assemblage dominated by southern beech Nothofagus spp. (fusca group), and the nonterrestrial assemblage is dominated by ice-indicative acritarch Leiosphaeridia spp. with some samples containing spores of the fresh water algae Zygnemataceae. Based on palynological concentrations recovered, the Victoria Valley and Beacon Valley may have been the site for vegetation refugia. Samples collected from Victoria Valley have concentrations ranging from 252.1 to 5191.1 gdw-1 and nonterrestrial derived palynomorph concentrations ranging from 735.6 to 2386.1 gdw-1. The Central Beacon Valley has a terrestrial-derived palynomorph concentration of 131.8 to 675.3 gdw-1. These concentration ranges are higher than other sample locations analyzed for this study such as the Olympus Range, Taylor Valley, and valleys located in the Asgard Range, with samples concentrations that are barren to 17.4 gdw-1 for the Olympus Range, barren to 1.4 gdw-1 for Taylor Valley, and barren to 39.6 gdw-1 sites in the Asgard Range. Based on the present study, the Victoria Valley and Beacon Valley regions acted as refugia for isolated pockets of vegetation to survive around the Mid-Miocene and >8.07±0.06 Ma based on their palynomorph assemblages and concentrations. These sites potentially were ideal locations where geological ... |
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