Notice from the Editor

Notice from the Editor from Volume 5, Number 2, 1971 of Earth Science Journal

Erosion by high intensity rainfalls in the lower Waikato

A high intensity rainstorm with rainfalls exceeding 10 inches in 24 hours on the Hunua Range is described, and some of its geomorphological and economic consequences discussed

The middle Waikato Basin and hills

The middle Waikato (or Hamilton) Basin is a roughly oval-shaped depression more than 80 km north to south and more than 40 km wide. The basin, except in the south, is almost completely surrounded by ranges up to 300 m high, broken by only a few gaps. In the south the basin floor rises gradually and merges with the dissected plateaux of the King Country

Aspects of the geomorphology of the Greywacke Ranges bordering the Lower and Middle Waikato Basins

The fault-bounded blocks which make up the Greywacke Ranges bordering the Lower and Middle Waikato Basins have a deep red-weathered regolith and are covered by mantles of volcanic ash which can be used for dating ground surfaces. The drainage texture is exceedingly fine compared with that of Dartmoor (U.K.) and Unaka Mountains (U.S.A.) This is attributable to rainfall type, regolith, vegetation cover and soil physical properties. The major types of mass movement are deep fossil slumps on upper slopes where the regolith is deep; debris slides on mid- and lower slopes where the regolith is thin; and seepage heads controlled by ground water conditions. The valley floors show both stream incision, and aggradation resulting from infill with mass movement debris. Deforestation has increased the frequency of mass movement during high intensity rainstorms and the slopes are at present becoming adjusted to changed equilibrium conditions

A flume for studying the relative erodibility of soils and sediments

A flume has been built for studying the erodibility of soils and sediments by gullying. It consists of two boxes containing undisturbed soil samples. One box is set above the other and water from a stilling tank passes over the soil of the upper box and falls onto the soil of the lower box causing lip and channel scour and plunge-pool erosion. The sediment is collected and measured, and a measure of erodibility related to discharge, length of test and sediment yield is thus available

Jet vortex generators for turbulent flow separation control

A parametric study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low speed turbulent flow over a two dimensional rearward-facing ramp. Results indicate that flow separation control can be accomplished with the level of control achieved being a function of jet speed, jet orientation (with respect to the free stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed)

The age of quaternary surfaces at Waihi Beach

The Waihi Beach surfaces were originally mapped and correlated with European surfaces of similar altitude by Kear and Waterhouse (1961). Exposures along the edges of the surfaces indicate that they are covered with volcanic ashes, the younger of which are of known age. It is the sub-ash surface which should be used for height correlations, and it is the most seaward ash-covered part of the surface which is preferred as the reference point for altitude studies. The heights of the surfaces may not correlate with positions of sea-level at the ages indicated by the ash beds

Geochronology (Re–Os and U–Pb) and fluid inclusion studies of molybdenite mineralisation associated with the Shap, Skiddaw and Weardale granites, UK

Late Devonian magmatism in Northern England records key events associated with the Acadian phase of the Caledonian-Appalachian Orogen (C-AO). Zircon U-Pb and molybdenite Re-Os geochronology date emplacement and mineralisation in the Shap (405·2±1·8 Ma), Skiddaw (398·8±0·4 and 392·3±2·8 Ma) and Weardale granites (398·3±1·6 Ma). For the Shap granite, mineralisation and magmatism are contemporaneous, with mineralisation being directly associated with the boiling of CO2-rich magmatic fluids between 300 and 450°C, and 440 and 620 bars. For the Skiddaw granite, the Re-Os age suggests that sulphide mineralisation occurred post-magmatism (398·8±0·4 Ma) and was associated with the boiling (275 and 400°C and at 375-475 bars) of a non-magmatic fluid, enriched in N2, CH4 and S, which is isotopically heavy. In contrast, the co-magmatic molybdenite mineralisation of the Weardale granite formed from non-fluid boiling at 476 to 577°C at 1-1·7 kbars. The new accurate and precise ages indicate that magmatism and Mo-mineralisation occurred during the same period across eastern Avalonia (cf. Ireland). In addition, the ages provide a timing of tectonism of the Acadian phase of the C-AO in northern England. Based on the post-tectonic metamorphic mineral growth associated with the Shap and Skiddaw granite aureoles, Acadian deformation in the northern England continued episodically (before ∼405 Ma) throughout the Emsian (∼398 Ma)