subsequent drilling throughout the Pacific has confirmed
this (Schlanger, 1963). However, post-Funafuti, the
importance of the antecedent platform was as a foil to
another idea in understanding the growth of coral reefs,
that is, glacial eustacy. In a series of controversial papers,
Daly (1910, 1915, 1917, 1919, 1934) proposed that global
glaciations had the effect of both lowering sea level and
reducing sea surface temperatures, the effects of both substantially impacting the growth of coral reefs. His glacialcontrol theory, applied initially to atolls, used the glacial
lowering of sea level to produce foundations, which were
then planated by wave abrasion as the effective process in
turning fringing reefs into barrier reefs and then into atolls
(Figure 1b). These ideas were extended by Daly himself
and by Vaughan (1914, 1919, 1923) to Florida and the
Bahamas as well as to the Great Barrier Reef. While some
of Daly’s evidence has been called into question (e.g., not
all atolls have the same depth; his proposed processes and
rates of processes are unrealistic, and his proposed timescales are wrong), there can be little doubt today that
glacio-eustatic sea-level fluctuations have profoundly
affected how we think about the nature of the platforms
on which today’s coral reefs have grown. The next step
was taken by Kuenen (1933, 1947) coupling glacially produced sea-level fluctuations and subsidence to sub-aereal
and marine intertidal erosion to produce partially or
completely planated antecedent platforms on which further reef development could occur. And then, in the
1940s, very important papers but in poorly distributed
publications, Japanese scientists (Yabe, 1942; Asano,
1942; Tayama, 1952) coupled glacio-eustatic sea-level fall
to the nature of the reef foundations for the first time. Thus
began the germ of a new set of ideas. The first two papers
were by Hoffmeister and Ladd (1944, 1945), which admitted to the reality of sea-level fall but placed the major
emphasis on a suitable substrate for subsequent reef
growth, that is, any bench or bank situated at a proper
depth in the coral seas is a potential reef foundation. In
the 1945 paper, however, they reported the results of
experiments simulating the effects of rainfall on an
exposed limestone surface (a slab of Solenhoffen limestone) as a way to explain the origin of raised atolls. They
inferred from their crude experiments that the saucer shape
of raised atolls may be related to solution. This was left to
MacNeil (1954) who accepted Kuenen’s coupling of glacial lowering of sea level and subsidence but invoked
sub-aereal erosion to produce the diagnostic annular rim
of atolls, which was therefore inherited from a period of
earlier sub-aereal erosion (Figure 2). The saucer-shaped
basin was therefore the logical consequence of sub-aereal
solution acting on exposed Pleistocene atoll foundations.
MacNeil (op.cit) emphasizes the importance of
limestone-solution processes involving surface and subsurface solution and re-deposition and surface case hardening in producing relief features inherited by subsequent
reef growth during an ensuing sea-level rise. The accent
was clearly placed on inheritance from an exposed eroded
surface. Thus, atoll lagoons form on eroded lows, and atoll
rims occupy the surrounding highs. For whatever reasons,
MacNeil’s ideas were not received with ultra-enthusiasm
by the scientific community.
Antecedence post-1974 – the purdy revolution
In 1974, Purdy (1974) published a seminal paper, inferring
cause and effect in linking reef shape to karst-induced
antecedent morphology. Drowned atolls reflect drowned
karst topography; reef passes originate as drainage
breaches in the solution rim; faroes are the karst product
of breaching; peripheral islands are exposures of the fossil
drainage divide, and spurs and grooves are expressions of
lapies. Thus, the karst-induced differences in relief are
perpetuated and indeed accelerated by growth, but reef
growth per se has little to do with the basic configuration.
Paradoxically, a paper proving that the Holocene reef off
the north Jamaica coast was a mere mantling of low sealevel Pleistocene terraces (Goreau and Land, 1974) was
published alongside Purdy’s karst revolutionary paper.
In marked contrast to MacNeil’s ideas, the 1974 paper
sparked a widespread rethink of the role of antecedence
and for a number of reasons: (1) Purdy’s ideas applied to
barrier reefs as well as atolls and therefore to a much wider
scientific community, (2) he discussed processes that were
important to the oil industry in developing porosity, once
again opening the subject to a science community outside
of the academic, (3) he coupled eloquent laboratory experiments to well-illustrated examples of mega-karst morphology from some of the world’s notable karst areas, and
(4) he used well-illustrated seismic data coupled to drillhole data across a major barrier reef complex (effectively
for the first time), which became well known through the
work of Ginsburg and coworkers (Ginsburg and James,
1976; James and Ginsburg, 1976) and Rutzler and
Macintyre (1982). Furthermore, when data was lacking he
resorted to compellingly acceptable eloquent deductions.
Like Hoffmeister and Ladd (1944), Purdy (1974) subjected
limestone blocks to acid rain and produced features analogous to both karst and modern reef forms (Figure 2). He
emphasized solution rims, enclosed depressions at various
scales, conical karst, tower karst, and karst marginal plains
as important natural and experimental features, which could
have analogs in both atolls and barrier reef systems. He
coupled glacially effected sea-level oscillations, subsidence, and sub-aereal erosion to explain their formation
(Figure 3). Atoll morphology derives from the development
of solution rims on emerged limestone masses; where rainfall is high, breaches in the karst rim give rise to subsequent
atoll-passes, while in the interior, a conical karst may
develop as antecedent foundations to lagoonal patch reefs;
also, collapse dolines may form as a consequence of extensive subterranean dissolution, the forerunner of “blue holes”
according to Purdy (1974). Alternately, where rainfall is
low, conical depressions (solution dolines) form within the
solution rim. The morphology of atolls and barrier reefs is
solution determined rather than growth predicated (Purdy
and Winterer, 2001) (Figure 4).
ANTECEDENT PLATFORMS
41
this (Schlanger, 1963). However, post-Funafuti, the
importance of the antecedent platform was as a foil to
another idea in understanding the growth of coral reefs,
that is, glacial eustacy. In a series of controversial papers,
Daly (1910, 1915, 1917, 1919, 1934) proposed that global
glaciations had the effect of both lowering sea level and
reducing sea surface temperatures, the effects of both substantially impacting the growth of coral reefs. His glacialcontrol theory, applied initially to atolls, used the glacial
lowering of sea level to produce foundations, which were
then planated by wave abrasion as the effective process in
turning fringing reefs into barrier reefs and then into atolls
(Figure 1b). These ideas were extended by Daly himself
and by Vaughan (1914, 1919, 1923) to Florida and the
Bahamas as well as to the Great Barrier Reef. While some
of Daly’s evidence has been called into question (e.g., not
all atolls have the same depth; his proposed processes and
rates of processes are unrealistic, and his proposed timescales are wrong), there can be little doubt today that
glacio-eustatic sea-level fluctuations have profoundly
affected how we think about the nature of the platforms
on which today’s coral reefs have grown. The next step
was taken by Kuenen (1933, 1947) coupling glacially produced sea-level fluctuations and subsidence to sub-aereal
and marine intertidal erosion to produce partially or
completely planated antecedent platforms on which further reef development could occur. And then, in the
1940s, very important papers but in poorly distributed
publications, Japanese scientists (Yabe, 1942; Asano,
1942; Tayama, 1952) coupled glacio-eustatic sea-level fall
to the nature of the reef foundations for the first time. Thus
began the germ of a new set of ideas. The first two papers
were by Hoffmeister and Ladd (1944, 1945), which admitted to the reality of sea-level fall but placed the major
emphasis on a suitable substrate for subsequent reef
growth, that is, any bench or bank situated at a proper
depth in the coral seas is a potential reef foundation. In
the 1945 paper, however, they reported the results of
experiments simulating the effects of rainfall on an
exposed limestone surface (a slab of Solenhoffen limestone) as a way to explain the origin of raised atolls. They
inferred from their crude experiments that the saucer shape
of raised atolls may be related to solution. This was left to
MacNeil (1954) who accepted Kuenen’s coupling of glacial lowering of sea level and subsidence but invoked
sub-aereal erosion to produce the diagnostic annular rim
of atolls, which was therefore inherited from a period of
earlier sub-aereal erosion (Figure 2). The saucer-shaped
basin was therefore the logical consequence of sub-aereal
solution acting on exposed Pleistocene atoll foundations.
MacNeil (op.cit) emphasizes the importance of
limestone-solution processes involving surface and subsurface solution and re-deposition and surface case hardening in producing relief features inherited by subsequent
reef growth during an ensuing sea-level rise. The accent
was clearly placed on inheritance from an exposed eroded
surface. Thus, atoll lagoons form on eroded lows, and atoll
rims occupy the surrounding highs. For whatever reasons,
MacNeil’s ideas were not received with ultra-enthusiasm
by the scientific community.
Antecedence post-1974 – the purdy revolution
In 1974, Purdy (1974) published a seminal paper, inferring
cause and effect in linking reef shape to karst-induced
antecedent morphology. Drowned atolls reflect drowned
karst topography; reef passes originate as drainage
breaches in the solution rim; faroes are the karst product
of breaching; peripheral islands are exposures of the fossil
drainage divide, and spurs and grooves are expressions of
lapies. Thus, the karst-induced differences in relief are
perpetuated and indeed accelerated by growth, but reef
growth per se has little to do with the basic configuration.
Paradoxically, a paper proving that the Holocene reef off
the north Jamaica coast was a mere mantling of low sealevel Pleistocene terraces (Goreau and Land, 1974) was
published alongside Purdy’s karst revolutionary paper.
In marked contrast to MacNeil’s ideas, the 1974 paper
sparked a widespread rethink of the role of antecedence
and for a number of reasons: (1) Purdy’s ideas applied to
barrier reefs as well as atolls and therefore to a much wider
scientific community, (2) he discussed processes that were
important to the oil industry in developing porosity, once
again opening the subject to a science community outside
of the academic, (3) he coupled eloquent laboratory experiments to well-illustrated examples of mega-karst morphology from some of the world’s notable karst areas, and
(4) he used well-illustrated seismic data coupled to drillhole data across a major barrier reef complex (effectively
for the first time), which became well known through the
work of Ginsburg and coworkers (Ginsburg and James,
1976; James and Ginsburg, 1976) and Rutzler and
Macintyre (1982). Furthermore, when data was lacking he
resorted to compellingly acceptable eloquent deductions.
Like Hoffmeister and Ladd (1944), Purdy (1974) subjected
limestone blocks to acid rain and produced features analogous to both karst and modern reef forms (Figure 2). He
emphasized solution rims, enclosed depressions at various
scales, conical karst, tower karst, and karst marginal plains
as important natural and experimental features, which could
have analogs in both atolls and barrier reef systems. He
coupled glacially effected sea-level oscillations, subsidence, and sub-aereal erosion to explain their formation
(Figure 3). Atoll morphology derives from the development
of solution rims on emerged limestone masses; where rainfall is high, breaches in the karst rim give rise to subsequent
atoll-passes, while in the interior, a conical karst may
develop as antecedent foundations to lagoonal patch reefs;
also, collapse dolines may form as a consequence of extensive subterranean dissolution, the forerunner of “blue holes”
according to Purdy (1974). Alternately, where rainfall is
low, conical depressions (solution dolines) form within the
solution rim. The morphology of atolls and barrier reefs is
solution determined rather than growth predicated (Purdy
and Winterer, 2001) (Figure 4).
ANTECEDENT PLATFORMS
41