1 10 2 https://theses.otagogeology.org.nz/files/original/8f855864fd4e7859573ea86af2a098c2.pdf fe4826353f29448ce1f177e2abd188cf Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Author last name Last name of the Author Mannering Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Ohneiser, Christian Abstract The Abstract for this thesis The Antarctic ice sheets are sensitive to changes in ocean temperature and are predicted to retreat in the coming centuries. Geological reconstructions of ancient ice margin retreat can offer insights into the potential future rates of change. However, a lack of well-dated sedimentary records near the ice margin in the Ross Sea has restricted the reconstruction of ice sheet retreat since the Last Glacial Maximum and the subsequent oceanographic changes. Paleomagnetic studies are capable of providing the precise age control required for paleoclimate reconstruction from marine sedimentary successions and also enable correlation between geographically distant records, enabling comparisons to be made on both regional and global scales. The study of magnetic grains within sediment (environmental magnetism) can provide additional insights into changing oceanographic conditions and can be used to reconstruct changing terrestrial erosion rates and sediment delivery patterns. This thesis discusses the paleomagnetic study of four sedimentary cores: RS15- LC100; RS15-GC101; RS15-GC102; and RS15-GC107. The cores were recovered from the Drygalski and Glomar Challenger basins on the Ross Sea continental shelf, and further offshore on the abyssal plain by the Korean Polar Research Institutes’ vessel the R/V Araon, in 2015. They are located in regions with greatly varying depositional and oceanographic environments, and range in age from Holocene to mid-late Pleistocene. Paleomagnetic and environmental magnetic studies are sparse in this region, with a lack of well constrained age models. U-channel subsamples were measured at the Otago Paleomagnetic Research Facility (OPRF) in a 2G Enterprises superconducting magnetometer. Each sample underwent alternating field (AF) demagnetisation, and the data analysed on orthogonal component vector plots. Puffin Plot software was used to determine the Characteristic Remanent Magnetisation (ChRM) of the sediment and to produce a magnetostratigraphy. In addition, magnetic mineral studies (hysteresis, IRM, FORC and TDMS) were carried out in order to create a record of the environmental magnetism. Paleomagnetic age models based on secular variation or relative paleointensity were not able to be constructed for RS15-LC100, RS15-GC101, and RS15-GC102, due to the lack of a coherent ChRM. The ChRM records for RS15-LC100 in particular were entirely unable to have a magnetostratigraphy produced due to significant variations in magnetisation direction down the entire core. These cores are likely be Holocene in age and will rely on radiocarbon dating to produce an age model. Rock magnetic data indicates that magnetite is the dominant remanence carrying mineral, with potential indicators of the diagenetic magnetic mineral greigite present in some cores which may contribute to the poor data quality. A paleomagnetic age model was successfully constructed for RS15-GC107. Downcore variation in ChRM inclination aligned with the calculated Geocentric Axial Dipole inclination and the magnetostratigraphy that was correlated with the geomagnetic polarity timescale. Because biostratigraphic constraints were unavailable two age models were produced. Both models contain the Brunhes-Matuyama reversal boundary, with the preferred model, which results in the least varying sedimentation rate placing the boundary (C1n - C1r.1r, 0.774 Ma) at approximately 530 cm down core. This model also places the upper boundary of the Jaramillo chron (C1r.1r - C1r.1n, 0.990 Ma) at approximately 725 cm, and the lower boundary of the Jaramillo chron (C1r.1n - C1r.2r, 1.071 Ma) at approximately 775 cm. Calculated sedimentation rates varied between 0.68 cm/kyr and 0.72 cm/kyr. Small quantities of IRD are present throughout the core, as evidenced by discrete intervals with poor quality of demagnetisation data. TDMS and FORC analyses did not indicate the presence of greigite or other minerals that may carry a CRM. Keywords New Zealand, Ross Sea, Antarctica, Magnetostratigraphy, RS15-LC100, RS15-GC101, RS15-GC102, RS15-GC107, Paleomagnetism, Environmental Magnetism, Age Model, Drygalski Basin, Glomar Challenger Basin, Brunhes-Matuyama, Reversal OURArchive handle The handle from the Otago University Research Archive (OURArchive) http://hdl.handle.net/10523/9900 OURArchvive access level Open Access Department The department where the student is studying primarily. Geology Thesis description Number of pages, maps, CDs, etc. 165 Pages A4 Named locality Named locality describing the field area location. Ross Sea, Antarctica Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Magnetostratigraphy and Environmental Magnetism of the RS15-LC100, RS15-GC101, RS15-GC102, and RS15-GC107 cores from the Ross Sea Subject The topic of the resource Paleomagnetism Creator An entity primarily responsible for making the resource Mannering, Henry Date A point or period of time associated with an event in the lifecycle of the resource 2020 Identifier An unambiguous reference to the resource within a given context 2020Mannering Age Model alluvial gold Antarctica Brunhes-Matuyama Cretaceous stratigraphy Drygalski Basin Environmental magnetism Glomar Challenger Basin gold magnetostratigraphy New Zealand paleomagnetism Reversal Ross Sea RS15-GC101 RS15-GC102 RS15-GC107 RS15-LC100 https://theses.otagogeology.org.nz/files/original/d3fc6493a25094a8fc4ad66f3586ab27.pdf fd6fbacdc75d5de676eb34208efa777d Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format MULTIPOLYGON (((165.459024571345026 -78.260975887577573,165.930153403187717 -78.275458748374291,165.880470623272714 -78.384796163202211,165.32149895585971 -78.358351090289432,165.459024571345026 -78.260975887577573)),((163.391037909385147 -78.228595263547234,163.887357474306356 -78.243236626491793,163.784154488444841 -78.350120025240315,163.240067291074126 -78.322582660464377,163.391037909385147 -78.228595263547234)),((159.226884147374847 -78.499508349075626,159.985105885787448 -78.550457251856272,159.699927940592261 -78.766278258193182,158.840943766587714 -78.705339607664101,159.226884147374847 -78.499508349075626))) Author last name Last name of the Author Anderson Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Wilson, G.S. Abstract The Abstract for this thesis Retreat of the Antarctic ice sheets since the Last Glacial Maximum (LGM) has been associated with sea-level rise and ocean warming on the ice sheet margins, but the significance and relative contribution to eustatic sea-level rise since this time has been difficult to quantify. This thesis presents new constraints for the timing and retreat of the Skelton Glacier in the Ross Embayment and grounded ice in the Ross Sea, the Ross Sea Ice Sheet (RSIS). Using two nunataks, Escalade and Tate peaks as a gauge for past ice sheet levels, glacial geologic evidence and ¹⁰Be and ²⁶Al cosmogenic-nuclide exposure ages provide new and direct constraints on the past extent and timing of retreat of the Skelton Névé over the Late Quaternary. Glacial geological and geochronological evidence from Escalade and Tate peaks show that between 288 ka and 40.3 ka, the ice surface experienced slow deflation, lowering from ≥1431 to 1363 metres above sea level (masl). Ice in the southern Skelton Névé lowered by ~50 m between 40.3 ka and ~13.6 ka. Records from the eastern margin of Escalade Peak indicate the ice surface of the Skelton Névé was between 50 and 106 m higher than present during the LGM. The ice surface elevation remained close to its maximum ice level prior to 17.2 ka and has thinned by at least 50 m to the present-day level since ~13.6 ka. Thinning continued after 8.7 ka, and likely reached the present-day ice level ~2 - 3 ka. This lateglacial-Holocene ice-surface lowering is asynchronous from other sites in the Transantarctic Mountains where increased snow accumulation has been reported to have caused thickening up glacier in the early to mid-Holocene. ¹⁰Be exposure ages from large (>1 m) boulders in southern McMurdo Sound show that the RSIS had an ice surface elevation ~520 masl on the eastern side of Mount Discovery during the LGM and the onset of deglaciation was ~13.1 ka. The ice surface lowered from ~520 to 234 masl between 13.6 ka and 9.3 ka; and from 234 masl to the present ice shelf between 9.3 ka and 6.6 ka. This late-glacial and Holocene chronology from southern McMurdo Sound is consistent with other records in the Ross Embayment, and implies the RSIS experienced rapid retreat during the early to middle Holocene. These results suggest that the majority of ice sheet thinning and retreat in the Skelton Névé and in southern McMurdo Sound began just after meltwater pulse 1A (MWP-1A), a period of abrupt sea-level rise of up to 20 m that occurred between ~14.7 ka and 14.3 ka. Thus, it is unlikely that the RSIS and outlet glaciers from the East Antarctic Ice Sheet (EAIS) that drain into the Ross Embayment made a significant contribution to eustatic sea-level rise at this time. From the distribution and petrography of glacial deposits and the retreat chronology in southern McMurdo Sound a two-stage ice flow model for McMurdo Sound was reconstructed: (1) Prior to ~18 ka an expanded Koettlitz Glacier lobe of ice owed north and northeast through the Brown Saddle during the LGM and coalesced with northward owing ice from the Ross Sea. (2) Retreat of the Koettlitz Glacier and perhaps other outlet glaciers then accommodated westward and northward ice flow north of Brown Peninsula, fed from grounded ice in the Ross Sea. These findings reveal that components of both the EAIS and West Antarctic Ice Sheet (WAIS) that drained into the Ross Sea contributed to lateglacial-Holocene sea-level rise. However, it is likely to be in response to warming of the Southern Ocean and sea-level rise from the retreat of the Northern Hemisphere ice sheets and the outer margins of the Antarctic. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/5613">http://hdl.handle.net/10523/5613</a> OURArchvive access level Abstract Only Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Antarctica McMurdo Sound Ross Sea Thesis description Number of pages, maps, CDs, etc. xii, 215 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2015Anderson Creator An entity primarily responsible for making the resource Anderson, Jacob Thomas Herd (Jacob) Date A point or period of time associated with an event in the lifecycle of the resource 2015 Title A name given to the resource Late Quaternary ice sheet thinning and retreat in southern Victoria Land, Antarctica Subject The topic of the resource Paleoclimatology Antarctica Exposure dating Holocene Last Glacial Maximum McMurdo Sound Ross Sea Skelton Glacier