Aim To assess the geological evolution and biogeographical implications of low mountain passes. In particular, we question the common biogeographical belief that major mountain belts form impervious physical barriers to biological dispersal, and that related taxa found on opposites sides of mountains are necessarily a result of vicariant tectonic processes. Location The Southern Alps of New Zealand form a long (500 km) narrow...

The Sutton Salt Lake is the only saline lake in New Zealand, and has formed in a windy cool‐temperate maritime climate. Consequently, the lake is distinctly different from most of the world's saline lakes that form in arid continental settings. Sutton Salt Lake forms annually in a shallow (5 m) bedrock‐floored depression c. 50 km from the nearest coast. The site receives c. 500 mm/year rainfall compared with coastal rainfall o...

Roads in the Puhipuhi area of Northland, New Zealand, have been surfaced with road aggregate derived from hydrothermally mineralised rocks, which contain iron sulphides (pyrite and marcasite). Oxidation of the iron sulphides results in localised acidification, typically to pH 3, on roads and in source quarries. This low pH is at least one pH unit more acidic than typical background pH of 4–5.5 in forested areas through which t...

The stream catchment containing the tailings dam complex at the Macraes mine, east Otago, New Zealand has three chemically distinct water types. ( 1) Natural groundwater has pH beween 6 and 8, and sulphate levels locally elevated to 30 ppm. The total carbonate/calcium (Ca) ratio is c. 2, consistent with carbonic acid dissolution of basement schist calcite. Sodium (Na) is strongly elevated over chloride, and these levels are do...