Geology Reference
In-Depth Information
(a)
(c)
Lo
Hi
Light intensity
I
d
=
I
0
exp[
0
−
kd
]
Light
Photosynthesis
Carbonate production
P
d
=
P
max
(tanh (
I
0
/
I
d
))
Chalker (1981)
10
Photosynthesis
Skeletal growth
20
Coral growth
G
d
=
G
max
(tanh (
I
0
/
I
d
))
M. annularis
growth
Coral growth
Reef accretion
30
Vertical reef growth
d
h
/
d
t
=
G
max
(tanh (
I
0
exp[
−
k
((
h
0
+
h
t
)
−
(
SL
0
+SL
t
))/I
k
])
18
(b)
16
14
40
12
10
8
6
4
2
After Bosscher (1992)
50
0
0
500
1000
1500
0
5
10
15
Coral growth (mm yr
−
1
)
Light intensity (
m
E m
−
2
s
−
1
)
Fig. 1.
(a) Summary of a quantitative model to predict coral growth and reef accretion with depth. (b) Growth rate for
the
Montastraea annularis
complex versus light intensity (measured in microEinsteins). The best-fi t line mimics the
hyperbolic tangent function, as predicted by Chalker (1981). (c) The relationship between coral growth and water depth.
Circles are actual growth rates determined by X-radiography of modern colonies. The shaded area is the predicted range
of coral-growth rates based on A and B. It has been generally assumed that while reef accretion will proceed at rates an
order of magnitude slower than coral growth, a similar depth-related trend (i.e. exponentially decreasing) is present. All
after Bosscher (1992).
METHODS
using all data that could be recovered from the
literature as well as unpublished information in
the author's archives. In the literature, each sample
was reported by species, depth below present sea
level and radiometric age. The analyses discussed
below compare accretion rates for reef intervals
dominated by
Acropora palmata
(Lamarck) versus
massive species across a wide palaeodepth range.
Because
A. palmata
is easily distinguished
from massive species in cores, no effort was
made to check the identifi cations reported in the
Reef accretion is generally defi ned as vertical
aggradation over time. This is in part an artefact
of the vertical orientation of cores from which
measurements are made. However, it also stems
from the realization that coral growth is strongly
controlled by light from the surface. While reefs
may build horizontally, this is generally held to
be the lateral expression of largely upward exten-
sion. In this study, accretion rates were calculated
