Upcot Station, Marlborough Region, New Zealandi

Regional Level Types
Upcot Station	- not defined -
Marlborough Region	Region
New Zealand	Country

Marine sandstones and coarser material overlain with more rounded sandstones and conglomerates that grade up into terrestrial sediments and coal measures. On top of these and intruded into them are basaltic volcanics, up to 1600m thick in the Awatere Valley. The flows are tilted and the Awatere River has cut a gorge through them. They have been named the Lookout Volcanics, from the high peak on Middlehurst Station, which was originally called Mowat's Lookout, from the Mowat family of Altimarlock Station.

In most places, the basalt flows lie on top of the sediments and coal seams, and all the older flows seem to have been on land. They show hexagonal jointing, and several layers were weathered before the next flow covered them. Fossil-bearing grits and marine tuffs (ash-layers) are found in the top 150m and contain material derived from the underlying basalt. The best-preserved fossils are in tuffs, and a 5 cm layer of belemnites was found between a tuff bed and an overlying basalt flow in the third gully below the road between Scrubby Creek and Castle River. There are also two thin bands of limestone almost entirely composed of Inoceramus fragments. The lavas in this area show pillow structures of normal porphyritic basalts containing coarser crystals of labradorite, titan-augite and olivine.

In the main flows, the basalt is commonly massive with fairly numerous visible crystals of titan-augite and scarcer olivine. Other basalts are finer-grained. Numerous cavities contain zeolites, calcite, and quartz. A single flow of white trachyte with a bright-red weathered top forms a conspicuous horizon about 300m below the summit of Mt Lookout and can be traced from the head of Middlehurst Creek for about a mile to the northeast. This rock is mostly oligoclase-andesine and sanidine feldspars with very sparse granular augite in a groundmass of devitrified glass.

Grey chalcedony with inclusions of natrolite crystals and calcite. Colours range from greys, white to pale amethyst.

The area is rugged and mountainous. Collectors may need permission of the station owner to access. Some material is likely to remain due to the area's remoteness. Similar minerals are found at nearby Mount Lookout at Middlehurst Station, Marlborough Region, New Zealand.

A visit, probably the early 1970's (Thornton) reported vugs on the slopes of Mount Upcot containing simple rhombs of deep salmon pink chabazite, with rarely analcime perched on it. At the base of the cliffs below Mount Upcot is stilbite, as sheaves and blades 2-3cms, some with analcime crystals, peach or paler pink. At the same location, there was chabazite and vugs of white levyne with half hexagonal shapes. Also, levyne was found in vugs with long silky overgrowths of offretite-erionite, white to pale cream.

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References