Green Point

BY NICK MORTIMER (GNS)
Accessibility: EASY
Steeply dipping Permian sandstones at Green Point (Nick Mortimer/GNS Science)
The rocky shore at Green Point in Bluff Harbour displays jointed and steeply dipping hornfelsed sandstones of the Permian Foreshore Group (Brook Street Terrane). Bedding is cut by basalt dikes. The wrecked hulks of scuttled ships create a surreal backdrop.
A flow-banded basalt dike cuts across bedding. Key for scale (Nick Mortimer/GNS Science).
Bedded sedimentary rocks of the Permian Foreshore Group (Brook Street Terrane) are exposed along the west side of Bluff Harbour. The tough and flinty nature if the rocks is caused by their being 'baked' by the Median Batholith gabbros which were emplaced as hot, liquid magma, about 1 km to the west.
Bedding, picked out by layers in the sandstones and mudstone dips 80 degrees to the SW. Some black basalt dikes cut across each other as well as cutting the sandstones and mudstones. Most dikes are homogeneous (without layers), but some dikes are internally layered - they have large and small crystals of dark green pyroxene up to 5mm in size that form layers parallel to the edges of the dike. These were created by the pulsating flow of crystal 'mushes' moving along the dikes as they opened.
Directions/Advisory

Turn off State Highway 1 between Invercargill and Bluff to the signposted Green Point Walkway (about 2 km north of the old Bluff Freezing Works). Park in the carpark at -46.5730, 168.3021.

The rock outcrops are only visible at low to mid tide.

Google Directions

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Accessibility: EASY

From the carpark walk along to the end of the Green Point Track (about 800 m). Step down onto the beach. The part closest to Bluff (south) is the most informative.

Features
Plutonic Metamorphic
Geological Age
Permian
Zealandia Evolution Sequence
Eastern Province (Mesozoic growth): 300 – 110 million years ago