Source, sea level and circulation effects on the sediment flux to the deep ocean over the past 15 ka off eastern New Zealand

The last post-glacial transgression and present highstand of sea level were accompanied by a reduction in the terrigenous flux to the deep ocean bordering the active convergent margin off the eastern North Island of New Zealand. Although in accord with long-established models of highstand shelf deposition, new data from giant piston core MD97 2121 (2314 m depth) reveal that the flux also varied with terrigenous supply and palaeocirculation. Between 15 and 9.5 ka, the flux reduced from 33 to 20 g/cm²/ka as supply declined with an expanding vegetation cover, and mud depocentres became established on the continental shelf. An increase from 20 to 27 g/cm²/ka during 9.5–3.5 ka coincided with a strengthened East Cape Current which probably introduced sediment from fluvial and shelf sources in the north. The flux profile shows no immediate response to the establishment of modern sea level 7 ka. However, accumulation decreased from 3.5 to 1 ka as more sediments were retained on the shelf, possibly under wind-strengthened, along-shelf currents. Over the last 1 ka, the flux decline halted under increased terrigenous supply during anthropogenic development of the land.Despite the proximity of the North Island's Central Volcanic Region, major eruptions caused only brief increases (centuries duration) in the terrigenous flux through direct deposition of airfall and possibly fluvial redistribution of onshore volcanic deposits. Frequent earthquakes also had little short-term effect on accumulation although such events, along with volcanism, probably contribute to the long-term high flux of the region.The other measured flux component, biogenic carbonate, reached maxima of 6 g/cm²/ka between 11 and 8.5 ka when nutrient-bearing waters of the East Cape Current dominated the palaeoceanography. After these peaks, carbonate accumulation declined gradually to modern levels of 3 g/cm²/ka.     

Geotechnical zonation and soil–structure interaction at Puerto Vallarta,México

Natural Hazards - We performed a seismic vulnerability assessment that involves geotechnical and building structure analysis for Puerto Vallarta, Mexico, a city located along the pacific coast....     

Review: Hydrogeology of Northern Mendoza (Argentina), from the Andes to the eastern plains,in the context of climate change

Hydrogeology Journal - In the drylands of Northern Mendoza, Argentina, water supply depends on rivers and groundwater. Climate change makes this region vulnerable due to the snow-glacial-melt...     

Find your own voice

Haley Gomez presents a guide to getting your voice heard in the media, aimed at early-career research scientists.     

The effects of acoustic-gravity waves on the K i 7699 line

We examine the effects of acoustic-gravity waves with long and short periods on the solar profile of the K i7699 line using a dynamic model of line formation.First we studied the kinetic equilibrium of the K i atoms in a static atmosphere confirming, with up-to-date atomic data and atmospheric model, that a good fit of the resonance line 7699 is possible only when non-LTE effects are accounted for.Then the static non-LTE line source function and lower-level population are used as input data for calculating the line formation in the presence of waves.The time behaviour of the synthetic profiles corresponding to 300 s and 30 s waves is extensively discussed. The characteristic redshift induced by the 30 s wave is explained within the framework of the S-S line formation model. Long-period waves yield an anticorrelation between the asymmetry at different residual intensities and the line core shift, as observed. The short-period waves with velocity amplitude of about 100 m s^–1 (at the base of the photosphere) produce a mean bisector whose lower part has a slope in agreement with the observed one. The efficiency of waves to produce macro and microturbulence is also discussed.Currently NAS/NRC Senior Research Associate at Sacramento Peak Obs., New Mexico, U.S.A.     

Explicit Fracture Network Modelling: From Multiple Point Statistics to Dynamic Simulation

This paper addresses the problem of explicit fractured media modelling in an operational case. On one side, realistic fracture models are mainly used for research purposes in order to investigate better the flow behaviour impacted by the complex multi-scale fracture network. Often, a very fine grid and hence an increased computation time are needed. On the other hand, an operational fractured reservoir is still generally modelled using an implicit fracture media representation. The upscaled petrophysical properties and dual media are defined on a coarse grid to limit the computational time of dynamic simulation. The challenge of this work is to demonstrate that an explicit fracture modelling is not reserved only for the research domain, but can be applied to an operational case study. The static model is constructed using a multiple point statistics approach in order to represent complex interaction patterns of fractures and faults observed at the analogue outcrop. The dynamic behaviour is simulated based on this spatial fracture network representation.