The Downs (West Coast) EarthCache
Hidden : 1/21/2016
Difficulty:
1.5 out of 5
Terrain:
4 out of 5

Size: Size: other (other)

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Geocache Description:


The Gouland Downs, a down-faulted remnant of a stripped Lower Tertiary peneplain surface, are unusual in that they are one of the few naturally bush-free areas below normal tree line in the uplands of North-West Nelson. Situated at an altitude of about 2,000 ft, between the southern end of the Wakamarama Range and the northern end of the Tasman Mountains, the Downs are traversed by the Heaphy Track. After descending from the ridge following the recommended Heaphy Track direction by DOC you will find yourself within the Mackay Downs at GZ.

High altitude vertical aerial photographs flown in 1963 revealed unexpectedly complex folds, dramatically outlined by beds of quartzite. The surface of the Downs, an area of approximately 12 square miles, slopes gently to the north but is cut by a series of more or less north-trending faults which have produced a shallow, stepped, graben-like structure with individual steps up to 100 ft high. To the north, the peneplain surface of the Downs is up thrown 800 ft at the steep east-west scarp of the Slate Range Fault, on the summit of which the peneplain surface is also preserved. Small mesas of lower Tertiary covering strata-limestone underlain by a few feet of quartz grit-remain in a few places on the peneplain surface, and being forested, stand out conspicuously. Elsewhere the leached quartzose rocks of the peneplain surface, coupled with the excessive rainfall, have inhibited the development of an appreciable soil horizon. What soil there is consists of a thin covering of gritty impervious clay, resulting in the unusual vegetative cover for this altitude, of flax, snow tussock, and stunted scrub. Although the interfluves are broad, nat, and waterlogged, the streams are incised in steep narrow gorges with numerous small waterfalls and cascades.



Please make your way to GZ were you will find a large bolder which will help answer the following questions:

1. Have a closer look and describe the rock's structure, minerals and crystal size.

2. Which colour can be found within the rock's structure?

3. Based on your findings for Q1/2 what type of rock did you discover?

Please log your find at the same time as your email me your answers. However, if your answers are incomplete or wrong you will be asked to provide more details. If this is not provided the log will be deleted.


Source: D. G. Bishop, Reclined folds and coaxial refolding in the paleozoic rocks of North-West Nelson, New Zealand Journal of Geology and Geophysics.

Additional Hints (No hints available.)



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