Browsing by Author "Rieser, U"

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    Mountain glacier chronology from Boulder Lake, New Zealand, indicates MIS 4 and MIS 2 ice advances of similar extent
    (Institute of Arctic and Alpine Research, 2008-11) McCarthy, A; Mackintosh, AN; Rieser, U; Fink, D
    Dating of past glaciation in New Zealand allows Quaternary climatic events to be identified in areas at a great distance from northern hemisphere ice sheets and associated climatic feedbacks. Moreover, climate reconstruction in New Zealand provides insight into the amount of climate change that occurred in the Southwest Pacific where zonal circulation is an important integrator of the climate signal. Boulder Lake is a relatively low-elevation cirque in a range of moderate-relief (similar to 1600 m) mountains in South Island of New Zealand, and it experienced cirque and valley glaciation during the Late Quaternary. Geomorphic mapping. Be-10 and Al-26 exposure. and luminescence dating provide evidence for glacial advances during the Last Glacial Cycle, specifically during Marine Isotope Stage 4 (MIS 4) and Marine Isotope Stage 2 (MIS 2). The MIS 4 advance was fractionally larger and is dated by a former ice-marginal lacustrine deposit (minimum age) with a basal Optically Stimulated Luminescence (OSL) sediment deposition age of 64.9 +/- 10 ka. Paired Be-10 and Al-26 constrain a slightly less extensive MIS 2 glacial advance to 18.2 +/- 1.0 and 17.8 +/- 0.9 ka, coincident with the Last Glacial Maximum (LGM). Glacial equilibrium-line altitudes during both MIS 4 and MIS 2 phases were similar to 960 in lower than the present. This corresponds to a cooling of 5-7 degrees C, taking possible precipitation variability into account. Our findings and a growing number of publications indicate that many temperate valley glaciers reacted differently to the major ice sheets during the Last Glacial Cycle, reaching their Maximum extent during MIS 4 rather than during peak global ice volume during MIS 2. © 2008, Institute of Arctic and Alpine Research
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    Stratigraphy and sedimentology of the longest terrestrial record in NE-Australia: Lynch’s Crater
    (Elsevier, 2007-07) Wust, R; Kershaw, P; Rieser, U; Jacobsen, GE; Deino, A
    Lynch’s Crater on the Atherton Tablelands in NE-Australia, formed some >200,000 years ago during an explosive eruption of basaltic material creating a maar more than 80 m deep. The crater walls are highly weathered and are blanketed by thick (>2 m) sequences of laterites that contain slates and other metasedimentary rocks (up to boulder size) and various types of volcanic rock fragments. Since the eruption, the maar has been filled with lake sediments that are topped by peat material and the recovered core was 64 m long. The basal sediments below 62.75 m are composed of massive grey silty-sandy clays with abundant rock fragments including basalts, vein quartz and other quartz-rich metasediments. The subsequent 50 m thick lake sediments are composed of massive and laminated sediments. The bottom lake sediments have frequent thick (up to > 2 cm) turbidite sequences while the top sediments have only few thin (max few mm) clay-rich turbidite deposits. Beside the turbidite layers, the lake sediments are either massive or laminated. Most of the sediments in particular in the upper 30 m are laminated. The varves are chemical varves with various colours from dark green, dark blue (vivianite) to black. The top 13–16 m (depending on the location in the crater) are composed of mainly minerotrophic peats and represent the past 60 ka. Geochemical analysis shows that Heinrich and Dangaard-Oeschger events can be detected. Here we present in detail stratigraphic and geochemical changes and present evidence for environmental changes of the entire core. The geochronology is based on C14 AMS, OSL and Ar-Ar dates.
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    Stratigraphy, timing and climatic implications of glaciolacustrine deposits in the middle Rakaia Valley, South Island, New Zealand.
    (Elsevier, 2010-08) Shulmeister, J; Thackray, GD; Rieser, U; Hyatt, OM; Rother, H; Smart, CC; Evans, DJA
    Stratigraphic interpretations and infrared stimulated luminescence (IRSL) ages document the glacial history of the Middle Rakaia Gorge section of the Rakaia Valley, Canterbury, New Zealand, during the last two glacial cycles. Sheets of glaciolacustrine sediments several tens of metres in thickness can be traced at least 10 km upstream of the Rakaia Gorge. The stratigraphic package is capped by outwash gravels associated with the last glacial maximum (LGM) advances. The dominant inferred sedimentary environments in the sequence are 1) pro-glacial and paraglacial lake beds, 2) sub-aqueous ice-contact fans, 3) sub-aqueous mass flow deposits 4) supraglacial dump material and 5) outwash gravels. Syndepositional deformation, associated with glacitectonic deformation, is common. The stratigraphy records glacier margin oscillations, including six significant advances. These occurred in early MIS 6, mid-MIS 6, MIS 5b (c100–90 ka), MIS 5a/4 (c 80 ka), mid-MIS 3 (c 48 ka), and late MIS 3 (c 40ka). All the post-MIS 6 advances can be corroborated from other sites in New Zealand and the timings appear to coincide with both Southern Hemisphere insolation minima and maxima, suggesting variable combinations of climatic forcing in New Zealand glaciation. © 2010, Elsevier Ltd.