Geology Reference
In-Depth Information
SOUTH
EQUATORIAL
CURRENT
EAST
AUSTRALIAN
CURRENT
LEEUWIN
CURRENT
Great
Barrier
Reef
AUSTRALIA
WEST
AUSTRALIAN
CURRENT
Study
Area
30˚S
Warm-water Carbonates
Cool-water Carbonates
WEST WIND
DRIFT
Cold Current
Warm Current
ZONE
120˚E
140˚E
Fig. 1.
Map of Australia showing major ocean currents, areas of cool- and warm-water carbonate deposition, and location
of study area.
calcareous organisms, and as substrates for
calcareous epiphytic growth is profound (Patriquin,
1972; Brasier, 1975; Wanless, 1981; Perry &
Beavington-Penny, 2005; Corlett & Jones, 2007).
The continental shelf of southern Australia,
south of 30°S and facing the Indian, Southern
and Pacifi c oceans (Fig. 1), is the largest area of
cool-water carbonate sedimentation on the globe
(James, 1997). Vast areas of the inner shelf seafl oor
here are covered with seagrasses. It has long been
known that the rates of sedimentation on these
cool-water, marine grass banks are much higher
than in contemporaneous offshore marine envir-
onments (Gostin
et al
., 1988; James, 1997), and
yet little is known about how these sediments are
generated and the precise role of seagrass in sedi-
ment production.
The purpose of this study is to document the
nature of such sediment production in a suite of
nearshore environments in southern Australia,
from the Great Australian Bight east to the Otway
shelf a distance of ~1300 km (Fig. 2). This paper
represents part of a PhD research project under-
taken by KMB, who was tragically killed in
Antarctica before the study could be fi nished.
The problem was conceived by NPJ and YB who,
together with AC, supervised the study, assembled
and completed the thesis, and wrote this paper.
SEAGRASSES IN SOUTHERN
AUSTRALIA
Introduction
Seagrasses are aquatic monocotyledons that con-
tinuously produce new blades, while shedding
old ones. Calcareous epiphytes that encrust this
renewable substrate are also continuously grow-
ing and being removed as the seagrass blades
are discarded. Southern Australia and Western
Australia are one of the world's most extensive
known areas of temperate seagrass (Kirkman &
Kuo, 1990). South Australia alone has 9612 km
2
(Edyvane, 1999a). The most extensive of these sea-
grass meadows occur in the clear, shallow, shel-
tered gulf waters of the Spencer Gulf (5520 km
2
)
and Gulf St. Vincent (1530 km
2
) (Fig. 2) (Lewis
et al.,
1997; Edyvane, 1999b). Twelve species of
