Identifier

etd-04032017-164241

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

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 processes such as erosion and transportation did not influence the geologic record, thus preserving these sites. The results in this study provide detailed information to be utilized for future expeditions into the region to precisely time vegetation’s demise within the McMurdo Dry Valleys.

Date

2017

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Warny, Sophie

DOI

10.31390/gradschool_theses.4468

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