NZ-INTIMATE members. 2007. Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ-INTIMATE project).

Evaluating conflicting theories about the influence of mountains on carbon dioxide cycling and climate requires understanding weathering fluxes from tectonically uplifting landscapes. The lack of soil production and weathering rate measurements in Earth's most rapidly uplifting mountains has made it difficult to determine whether weathering rates increase or decline in response to rapid erosion. Beryllium-10 concentrations in soils from the western Southern Alps, New Zealand, demonstrate that soil is produced from bedrock more rapidly than previously recognized, at rates up to 2.5 millimeters per year. Weathering intensity data further indicate that soil chemical denudation rates increase proportionally with erosion rates. These high weathering rates support the view that mountains play a key role in global-scale chemical weathering and thus have potentially important implications for the global carbon cycle.

a b s t r a c tThe Kawakawa/Oruanui tephra (KOT) is a key chronostratigraphic marker in terrestrial and marine deposits of the New Zealand (NZ) sector of the southwest Pacific. Erupted early during the Last Glacial Maximum (LGM), the wide distribution of the KOT enables inter-regional alignment of proxy records and facilitates comparison between NZ climatic variations and those from well-dated records elsewhere. We present 22 new radiocarbon ages for the KOT from sites and materials considered optimal for dating, and apply Bayesian statistical methods via OxCal4.1.7 that incorporate stratigraphic information to develop a new age probability model for KOT. The revised calibrated age, AE2 standard deviations, for the eruption of the KOT is 25,360 AE 160 cal yr BP. The age revision provides a basis for refining marine reservoir ages for the LGM in the southwest Pacific.Published by Elsevier Ltd.

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The eastern Sahara Desert is one of the most climatically sensitive areas on Earth, varying from lake-studded savanna woodland to hyper-arid desert over the course of a glacial-interglacial cycle. In presently arid Sudan there is widespread evidence that a very large freshwater lake once filled the White Nile River valley. Here we present the first quantitative estimate for the dimensions of the lake and a direct age for the emplacement of one of the shorelines. Using a profile dating approach with the cosmogenic nuclide 10 Be, we estimate an exposure age of 109 ± 8 ka for this megalake, indicating it formed during the last interglacial period. This age is supported by optically stimulated luminescence dating of Blue Nile palaeochannels associated with the lake. Using a high-resolution digital elevation model we estimate that the lake was more than 45,000 km 2 in area, making it comparable to the largest freshwater lakes on Earth today. We attribute the lake's existence to seasonal flood pulses as a result of local damming of the White Nile by a more southerly position of the Blue Nile and greatly increased precipitation associated with a super monsoon.

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The northeast-striking, dextral-reverse Alpine fault transitions into the Marlborough Fault System near Inchbonnie in the central South Island, New Zealand. New slip-rate estimates for the Alpine fault are presented following a reassessment of the geomorphology and age of displaced late Holocene alluvial surfaces of the Taramakau River at Inchbonnie. Progressive avulsion and abandonment of the Taramakau fl oodplain, aided by fault movements during the late Holocene, have preserved a left-stepping fault scarp that grows in height to the northeast. Surveyed dextral (22.5 ± 2 m) and vertical (4.8 ± 0.5 m) displacements across a left stepover in the fault across an alluvial surface are combined with a precise maximum age from a remnant tree stump (≥1590-1730 yr) to yield dextral, vertical, and reverse-slip rates of 13.6 ± 1.8, 2.9 ± 0.4, and 3.4 ± 0.6 mm/yr, respectively. These values are larger (dextral) and smaller (dip slip) than previous estimates for this site, but they refl ect advances in the local chronology of surfaces and represent improved time-averaged results over 1.7 k.y. A geological kinematic circuit constructed for the central South Island demonstrates that (1) 69%-89% of the Australian-Pacifi c plate motion is accommodated by the major faults (Alpine-Hope-Kakapo) in this transitional area, (2) the 50% drop in slip rate on the Alpine fault between Hokitika and Inchbonnie is taken up by the Hope and Kakapo faults at the southwestern edge of the Marlborough Fault System, and (3) the new slip rates are more compatible with contemporary models of strain partitioning presented from geodesy.