New Zealand Journal of Geology and Geophysics abstracts
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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