| |
240,000
years ago, sea level stood approximately
8 metres above its present level. The high wave-energy environment
had an erosive effect on Jurassic
and cretaceous sediments, creating a platform which enabled
the initiation of a coral reef formation. Sea levels dropped
and rose again, fluctuating around the present-day level.
A recession of the sea line leads to the exposition of marine
sediments, such as beach sands and coral formations. These
marine sediments, under the influence of land erosion, are
subsequently covered with terrestrial sediments. The erosive
action of waves on a growing reef leads to the transport
of coral rubble further inland. A situation similar to this
must have existed as we can find layers of sand and pebbles
enclosed by calcareous material.
A major marine transgression of the sea initiated a second
coral reef-building process much larger than the first one.
It is still disputable as to how high sea level rose 125,000
years ago. Some authors suggest 30 metres
above present sea level. Recent publications speak of 20
metres. Nevertheless, this rise in sea level represents
the maximum level in the history of the coral reef formation
corresponding to the last interglacial period. It is responsible
for the majority of today's fossil coral reef.
Sea level has gradually fallen since then. The sequence
of various terraces, which we see along the beach and further
inland as well as underwater, represent still-stands of
the sea level of varying duration during this general fall
of the sea level. The ocean line might even have risen for
a short time (in geological terms), but the general trend
was that marine sediments were emerging more and more and
being covered by terrestrial deposits. Theories on how far
sea level must have fallen vary from - 50 to - 120 metres.
30,000 years ago, sea level passed its present
level and defined our reef platform as we see it today.
At around the last glacial maximum 20,000 years ago,
sea level must have reached its minimum. Sea level rose
again to its present level 7,000 years ago. |
