existing Milencatan Limestone and corals settled on
preexisting highs about 80 m behind today’s reef margin.
Between 5,500 and 4,700 year B.P. corals accreted primarily under rising sea-level conditions and produced high
buttresses dominated by corymbose Acropora and thick
algal crusts. Large Porites mounds occurred in protected
areas. Around 4,700 year B.P. sea-level rise slowed and
the reefs caught up to the surface (then around þ2.5 to
3 m above present sea level; Bell and Siegrist, 1988).
Maximum sea level was at $4,200 year B.P. on Rota
and Guam (Kayanne et al., 1993; Pirazzoli and
Montaggioni, 1988; Dickinson, 2000). Coral frameworks
were then encrusted by digitate coralline algae, which Bell
and Siegrist (1988) and Kayanne et al. (1993) interpret as
Mariana Islands, Coral Reef Geology, Figure 1 The Mariana Islands, consisting politically of Guam and the Commonwealth of the
Northern Mariana Islands, the westernmost territories of the USA.
664
MARIANA ISLANDS, CORAL REEF GEOLOGY
preexisting highs about 80 m behind today’s reef margin.
Between 5,500 and 4,700 year B.P. corals accreted primarily under rising sea-level conditions and produced high
buttresses dominated by corymbose Acropora and thick
algal crusts. Large Porites mounds occurred in protected
areas. Around 4,700 year B.P. sea-level rise slowed and
the reefs caught up to the surface (then around þ2.5 to
3 m above present sea level; Bell and Siegrist, 1988).
Maximum sea level was at $4,200 year B.P. on Rota
and Guam (Kayanne et al., 1993; Pirazzoli and
Montaggioni, 1988; Dickinson, 2000). Coral frameworks
were then encrusted by digitate coralline algae, which Bell
and Siegrist (1988) and Kayanne et al. (1993) interpret as
Mariana Islands, Coral Reef Geology, Figure 1 The Mariana Islands, consisting politically of Guam and the Commonwealth of the
Northern Mariana Islands, the westernmost territories of the USA.
664
MARIANA ISLANDS, CORAL REEF GEOLOGY