Geology of Coal hill.

Mackay, Duncan Ross.

A small section of the Dun Mountain Ophiolite Belt is mapped in the Coal Hill area, Northern Southland.
Ophiolitic rocks are present in two distinctively different melange belts, termed the Western Melange and the Eastern Melange. The Western Melange contains serpentinised ultramafite and microgabbro inclusions in a sheared serpentinite matrix. A large inclusion within this melange, termed the Coal Hill Inclusion, consists of spilite and associated volcanogenic sediments and is correlated with upper Livingstone terrane and basal Maitai Group, the Upukerora Formation. The Eastern Melange is characterized by a varied assemblage of rocks, including microgabbro, spilitic volcanic, conglomerate, sandstone, argillite and Atomodesmatinid limestone. A blue-grey Tertiary mudstone is also exposed in this Eastern Melange. A large sedimentary broken formation occurs within the Eastern Melange and is further broken to form part of the melange in the Windley River area.
A small, coherent sliver of lower Livingstone microgabbro has a gradational contact with the Western Melange and is fault bounded to the west.
This same fault also separates the melange units from Maitai Group rocks. The basal Upukerora Formation consists mainly of polymict breccias, together with minor interbedded sandstones and limestones. Stratigraphically overlying the Upukerora Formation is the Tramway Formation, composed of fine, grey sandstones and uncommon tuffs and associated arkosic rocks.
Two infaulted slivers of Tertiary rocks are mapped in the area. Lithologies include fine, grey sandstones, occasionally with pebbly layers and a probable non-marine rock, with lignitic layers and lenses.

200 p. : ill., maps ; 30 cm.

1982Mackay

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