Examining the Mid- Brunhes Event in the Terrestrial Arctic: an Organic Geochemical Record from Lake El’gygytgyn, Russia

• Main Author: Habicht, Mary Helen
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2015
• Subjects: paleoclimate; biogeochemistry; Mid-Brunhes Event; Arctic; Earth Sciences
• Online Access: https://scholarworks.umass.edu/masters_theses_2/272; https://doi.org/10.7275/7486638; https://scholarworks.umass.edu/context/masters_theses_2/article/1299/viewcontent/MHH_thesis_full_final_formatting_edits.pdf

The characteristic glacial and interglacial cycles of the Pleistocene underwent a climatic transition at ~430 ka known as the Mid- Brunhes Event (MBE). Many studies, particularly from the Southern Hemisphere have noted that after this transition, the amplitude of the climatic cycles increased. Despite the indication of an MBE signal in many globally distributed paleoclimate records, the geographic extent of the climatic transition remains unknown and its presence in northern hemisphere and terrestrial records is debated. Lake El’gygytgyn is located in the far- east Russian Arctic and provides the longest, most continuous record of Arctic climate (3.6 Ma). This study examines organic biomarkers in the Lake El’gygytgyn sediment core to determine if the MBE is expressed in the terrestrial Arctic. The paleoclimate reconstruction spans the interval of 340- 730 ka at a resolution of ~3 ka. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are utilized to reconstruct temperature and plant leaf wax n-alkanes are used to examine vegetation changes. Statistical analysis of this, and other existing proxy data, indicates that a signal of the MBE is preserved in the Lake El’gygytgyn sediment record. BrGDGT temperature reconstructions suggest the terrestrial Arctic experienced both the warmest interglacials and coldest glacial periods after the MBE climatic transition. Arid glacial intervals and wetter interglacials are recorded by changes in the average chain length of n- alkanes, with wetter interglacials predominating after the MBE.