New Zealand Journal of Geology and Geophysics abstracts

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Early-Middle Jurassic stratigraphy of the Fortrose-Chaslands region, southernmost South Island, New Zealand

Mike S. Pole

Department of Botany
University of Queensland
Brisbane, QLD 4072, Australia

Abstract  The 40 km of coastline from Fortrose to Chaslands Mistake (southeastern South Island, New Zealand) comprises sediments that are part of the Early-Middle Jurassic of the Murihiku Terrane. The sediments are dominantly fluvial with some marine beds and alluvial fan deposition, and display an evolution of fluvial style which progresses from perennial flow to seasonal flow. The McPhee Cove Conglomerate is a prominent unit to the north. It has been used to separate two formations which would otherwise, on inherent lithological grounds, be difficult to distinguish. This paper discusses several similar conglomerates which occur in the south, but which are separated from the type area of the McPhee Conglomerate by major tectonic disruption. Hence, the existing lithostratigraphic nomenclature to the north, including the McPhee Cove Conglomerate, cannot be simply extended southwards. The Fortrose-Chaslands area appears to consist of two tectonic blocks, the Slope Point Block and the Brothers Block, which are separated from each other and from the adjacent Papatowai Block by major strike faults (or fault zones). A change is proposed to the existing stratigraphy which involves recognising all terrestrial sediments as part of the False Island Formation. Four prominent clast-supported conglomerate horizons are named as members of the False Islet Formation: the White Head Conglomerate, Black Bluff Conglomerate, Hoiho Conglomerate, and Slope Point Conglomerate Members. The latter contains five named conglomerate beds.

Keywords  Murihiku Terrane; Jurassic; Gondwana; conglomerate; fossil forest; fluvial sedimentology; White Head Conglomerate; Black Bluff Conglomerate; Hoiho Conglomerate; Slope Point Conglomerate; new stratigraphic names

G02047; Online publication date 25 February 2004
Received 5 September 2002; accepted 13 October 2003
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 129–139
0028–8306/04/4701–0129 © The Royal Society of New Zealand 2004

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