Geological History, Features of Geomorphology
9
-:o~- --- ---- -- -~
-wo - - - - - - - - - - - - - - -
-
-7,f0~
-7'/0 -7211 -100 -50
-50
-//0
-20
11
r
Fig. 1.3. Eustatic fluctuations of sea level (L, m) during the last 140000 years; Ttime, 10 3
years. (After Chappell 1981; Potts 1983)
/I,
0
'I
/J
12
76
6'
'I
2
0
T
Fig. 1.4. Change in sea level (A) and reef growth in time (B) during the Holocene
transgression. Numbers by curve B indicate rates of reef growth at various periods of
transgression, m 10 3 years-I; T age of reef, 10 3 years; H depth of reef column down from
the modern surface of reef flat, m. (After Thorn et al. 1978; McLean et al. 1978)
after the glaciation period next in turn died and were subjected to
atmospheric erosion. After following elevations of the sea level the reefs
extended to grow up at the base of these eroded ancient reef platforms.
Therefore, intensive reef growth proceeded even under conditions of
periodic exposures. Thus, the platforms of Pleistocene reefs were formed,
which in some places attained a thickness of hundreds of meters. Those
processes went on until 110-120 x 10 3 years B. P., when a large glaciation
caused the descent of the sea level by over 50m, which continued then with
interruptions till the last Wiirm glaciation 25000-16000 years B.P., when the
sea-level dropped by 100-130 m (Fig. 1.3). Then its quick rise started and
went on until 5000 years B.P. This is known as the Holocene transgression
(Chappell 1983). Its rate with reference to the coastal line was about 10 min
10- 3 years (Fig. 1.4). Around 7000 years B.P. the rate of transgression
slowed down. At 5000-4000 years B.P. it stoped and then descended again
I-2m till now (Thorn et al. 1978). When the rising ocean level reached the
surface of the exposed Pleistocene reef platforms between 12000-8000 years
B.P., the growth of reefs started on them again. This happened when the
9
-:o~- --- ---- -- -~
-wo - - - - - - - - - - - - - - -
-
-7,f0~
-7'/0 -7211 -100 -50
-50
-//0
-20
11
r
Fig. 1.3. Eustatic fluctuations of sea level (L, m) during the last 140000 years; Ttime, 10 3
years. (After Chappell 1981; Potts 1983)
/I,
0
'I
/J
12
76
6'
'I
2
0
T
Fig. 1.4. Change in sea level (A) and reef growth in time (B) during the Holocene
transgression. Numbers by curve B indicate rates of reef growth at various periods of
transgression, m 10 3 years-I; T age of reef, 10 3 years; H depth of reef column down from
the modern surface of reef flat, m. (After Thorn et al. 1978; McLean et al. 1978)
after the glaciation period next in turn died and were subjected to
atmospheric erosion. After following elevations of the sea level the reefs
extended to grow up at the base of these eroded ancient reef platforms.
Therefore, intensive reef growth proceeded even under conditions of
periodic exposures. Thus, the platforms of Pleistocene reefs were formed,
which in some places attained a thickness of hundreds of meters. Those
processes went on until 110-120 x 10 3 years B. P., when a large glaciation
caused the descent of the sea level by over 50m, which continued then with
interruptions till the last Wiirm glaciation 25000-16000 years B.P., when the
sea-level dropped by 100-130 m (Fig. 1.3). Then its quick rise started and
went on until 5000 years B.P. This is known as the Holocene transgression
(Chappell 1983). Its rate with reference to the coastal line was about 10 min
10- 3 years (Fig. 1.4). Around 7000 years B.P. the rate of transgression
slowed down. At 5000-4000 years B.P. it stoped and then descended again
I-2m till now (Thorn et al. 1978). When the rising ocean level reached the
surface of the exposed Pleistocene reef platforms between 12000-8000 years
B.P., the growth of reefs started on them again. This happened when the