Little Ben Sandstone, Maitai Group (Permian): nature and extent in the Hollyford-Eglinton region, South Island, New Zealand

Abstract

The Upper Permian Matai Group and its constituent formations of the Nelson Regional Syncline may be extended across the Alpine Fault into the Key Summit Regional Syncline, southern South Island. The Bryneira Group and its constituent formations are in most respects indistinguishable from the Maitai, and their usage should be discontinued in favour of the senior synonym. Little Ben Sandstone (previously mapped in Southland and Otago as Key Summit Sandstone) comprises distinctive green, quartz-deficient, vol-canogenic strata which are exposed extensively in the Eglinton-Hollyford region. Stratigraphy, field sedimentology, petrography (sedimentary and metamorphic), and chemistry of Little Ben rocks are described. It is suggested that Little Ben sediments were derived from a basaltic-andesitic volcanic arc and were deposited by mass flow processes in coalescing submarine fans flanking the arc.