A distributed mass-balance model is used over a 10-year period for the re-analysis of a glaciological mass-balance time series obtained from Brewster Glacier, New Zealand. Mass-balance modelling reveals glaciological mass balance has been overestimated, with an average mass loss of −516 mm w.e. a−1 not captured by observations at the end of the ablation season, which represents 35% of the annual mass balance. While the average length of the accumulation season (199 days) remains longer than the ablation season (166 days), melting is not uncommon in the core part of the accumulation season, with 2–32% of total snowfall being melted. Refreezing of meltwater is also important, with 10% of surface and subsurface melt being refrozen in the present climate. Net radiation, driven primarily by net shortwave radiation, is the main contributor to melt energy, with melt variability mainly influenced by the turbulent heat fluxes, net longwave radiation and the heat flux from precipitation in the ablation season. Snowfalls in summer are an important moderator of melt, highlighting the critical role of the ice-albedo feedback and phase of precipitation on seasonal mass balance. A complete homogenisation of the long-term glaciological mass balance for Brewster Glacier is still required.

At time-scales of 102 to 105 years, erosion by rivers, landslides and glaciers can exceed 5 mm/y. Sustained denudation at these rates is sufficient to account for many of the rapid rates of unloading or cooling that are revealed by geobarometric or thermochronologic studies. Because feedbacks exist among many surface processes, determinations of erosion rates on a few geomorphic processes can be adequate to estimate mean rates across an entire landscape. Rates of fluvial and glacial incision exert a dominant control on landscape lowering, because these rates set the local base level and modulate the flux from adjacent hillslopes. When rates of deformation are sufficiently rapid and sustained, a collisional orogen approaches a dynamic equilibrium or topographic steady state. Due to variations in erosion rates as a function of Late Cenozoic climate changes, such a steady state should be defined at time-scales longer than one climate cycle. During dynamic equilibrium, the geomorphic system displays a predictable configuration of interacting rivers, hillslopes and glaciated process zones. A dynamic equilibrium appears to prevail near Nanga Parbat, Pakistan, and the Southern Alps of New Zealand, where spatial variations in geomorphic erosion rates mimic variations in bedrock cooling rates at time-scales of 106 y.

Zoned barian muscovite (2.52-5.66% BaO) and unzoned biotite (0.99-1.77% BaO) occur in two amphibolite grade metacherts of the Alpine schists, Southern Alps, New Zealand. The Ba-micas are associated with quartz-chlorite-Mn-garnet-tourmaline-apatite-sulphide ± oligoclase ± rutile ± magnetite ± ankerite. Increasing Ba (core to rim) in the muscovite is accompanied by a decrease in Si, Ti, Fe + Mg, and K and an increase in [4]Al, [6]Al, and Na. The main substitution that accounts for entry of Ba into both micas is [A]Ba2+ + [4]Al3+ ⇋ [A]K+ + [4]Si4+ and possibly [A]Ba2+ ⇋ [A]K+ + □. Compositional variation of the muscovite is also governed by the substitutions, [6]Al3+ + [4]Al3+ ⇋ [6](Mg,Fe)2+ + [4]si4+, and [A]Na+ ⇋ [A]K+. The presence or absence of oligoclase, rutile, magnetite and Mg/(Mg + Fe) ratio of coexisting biotite control the Na, Ti, Fe and Mg contents of muscovite in the respective metacherts. Important variables controlling the occurrence of Ba-mica is the Ba-rich composition of the metacherts (1387 and 2741 ppm Ba) and metamorphic grade. In metacherts, siliceous and quartzofeldspathic schists with <1000 ppm Ba barium increases with increasing K2O content indicating that in K-feldspar-absent rocks barium is mainly contained in micas (<0.70% BaO). In greenschist facies metacherts and siliceous schists with high Ba (>1000 ppm) and low K2O, barian micas are not present and most of the Ba occurs in baryte ± barian carbonate with implication of a significant original hydrothermal-hydrogenous input. Although low grade illite/sericite/smectites containing Ba are the most likely precursor of the barian micas in the metacherts, strong marginal Ba enrichment in the muscovite indicates a later Ba-metasomatism resulting from the breakdown of baryte under reducing conditions during amphibolite facies metamorphism.

During the Last Glacial Maximum (LGM) the Tagliamento glacier delivered large amounts of sediment to the Cormor alluvial megafan on the southern Alpine foreland basin. To build a chronology of Late Pleistocene glacier fluctuations and assess the timing of the transition from interstadial to glacial conditions, we have performed radiocarbon (14C) dating on peat and macrofossil samples obtained from a drilling core from the distal Cormor megafan. Our chronology records fluvial and glaciofluvial aggradation from the end of MIS 3 until the end of the LGM. It shows a rapid transmission of signals of environmental change along the Cormor megafan, so that changes in the activity of the Tagliamento glacier directly affect glaciofluvial sedimentation. Our data demonstrate that the intrinsic heterogeneity of peat is most critical for the reliability and reproducibility of the obtained 14C ages. Macrofossil subsamples give evidence for significant mixing of organic components of different ages within single peat samples. Sample heterogeneity is also underlined by the results obtained from testing of different laboratory precleaning methods. Our results suggest that a rigorous ABA pretreatment is sufficient for peat cleaning. In contrast, the chemically stronger ABOX methods appear to rapidly degrade the peat, particularly destroying older organic components.

U–Pb zircon ages from volcanic rocks of Early Permian age (Southern Alps, Lombardy), associated with fault-controlled transtensional continental basins, were determined with the laser ablation (LA)-ICP-MS technique. Four samples were collected at the base and at the top of the up to 1000 m thick volcaniclastic unit of the Cabianca Volcanite. This unit pre-dates the development of a sedimentary succession that still contains, at different stratigraphic levels, volcanic intercalations. Age results from a tuff in the basal part of the unit constrain the onset of the volcanic activity to 280 ± 2.5 Ma. Ignimbritic samples from the upper part of the unit show a large scatter in the age distribution. This is interpreted as the occurrence of antecrystic and autocrystic zircons. The youngest autocrystic zircons (c. 270 Ma) are thus interpreted as better constraining the eruption age, constraining the duration of the volcanic activity in the Orobic Basin to about 10 Ma. The new geochronological results compared with those of other Early Permian basins of the Southern Alps reveal important differences that may reflect (1) a real time-transgressive beginning and end of the volcanic activity or (2) the complex mixing of antecrystic and autocrystic zircon populations in the analysed samples.

We apply fission-track thermochronology to shed new light on the tectonic history of Zealandia during Late Cretaceous continental extension and the onset of Late Tertiary mountain building in the Southern Alps of New Zealand. The Southern Alps are one of the fastest erosionally exhuming mountain belts on Earth. Exhumation of the Bonar Range in Westland just to the northwest of the Alpine Fault is orders of magnitude slower. We report apatite and zircon fission-track ages from samples that were collected along an ENE–WSW profile across the central Bonar Range, parallel to the tectonic transport direction of a prominent ductile fabric in the basement gneiss. Zircon fission-track (ZFT) ages show a large spread from 121.9 ± 12.1 Ma to 74.9 ± 7.2 Ma (1σ errors). The youngest ZFT ages of 78 to 75 Ma occur at low elevations on either side of the Bonar Range and become older towards the top of the range, thereby showing a symmetric pattern parallel to the ENE-trending profile across the range. Age–elevation relationships suggest an exhumation rate of 50–100 m Ma−1. We relate the ZFT ages to slow erosion of a tectonically inactive spot in the Late Cretaceous magmatic arc of Zealandia. Therefore, the first main significance of the paper is that it demonstrates that not all of 110–90 Ma Zealandia was necessarily participating in extreme core complex-related extension but that there were enclaves of lithosphere that underwent slow erosion. The apatite fission-track (AFT) ages range from 11.1 ± 1.9 Ma to 5.3 ± 1.0 Ma and age–elevation relationships suggest an exhumation rate of c. 200 m Ma−1. We relate the AFT ages to the inception of transpressive motion across the Alpine Fault and modest exhumation in its footwall in Late Miocene times. If so, the second significant point of this paper is that transpressive motion across the Alpine Fault was already under way by c. 11 Ma.

Microstructural analysis and P–T estimates of metamorphic pebbles in Permian conglomerates of the Central Southern Alps, representing the erosion product of the collapsing Variscan chain, are the discriminating tools for determining the metamorphic sequences representing potential sources of the conglomerates. In the selected case, basement units are precisely outlined on the basis of quality P–T–d–t paths that allow reconstruction of their metamorphic evolutions (tectonometamorphic units); this facilitates individuation of the basement sources with much better confidence. The lower Permian volcaniclastic sequence of the Eastern Orobic Basin, which overlies the Variscan Val Vedello basement, comprises the Aga and Vedello conglomerates, which are the oldest deposits containing a considerable amount of up to metre-sized metamorphic pebbles. Microstructural and mineral chemical data on metamorphic pebbles of the Aga and Vedello conglomerates were used to infer quantitative pre-Permian P–T evolutions, which are compared with those of the tectonometamorphic units constituting the surrounding Southalpine metamorphic basement. Two types of P–T evolution are recorded in the metamorphic pebbles of Aga and Vedello conglomerates: Type 1 is characterized by an amphibolite-facies imprint, followed by greenschist retrogression; Type 2 is characterized by three successive greenschist-facies re-equilibrations. The Type 1 P–T evolution of metamorphic pebbles matches with that of the adjacent tectonometamorphic unit of the Val Vedello basement. Type 2 is similar to those recorded in units B and C of the North East Orobic basement, and it differs from that of the adjacent Val Vedello basement. This suggests that the Aga and Vedello conglomerates were fed by two different basement sources: one consisting of the present day Val Vedello basement, and the other compatible with units B and C of the North East Orobic basement. According to the P/T ratios of the Tmax–PTmax imprints, both basement sources recorded the Variscan collision but at a different crustal level. The age (c. 278 Ma) of the Aga and Vedello conglomerates constrains the minimum exhumation age for their basement sources.