Geological History, Features of Geomorphology
5
A
Sf.
c
Sl
~
I'+T"TI
~
E888888 J L.±....±..J 2 ~ J
Fig. 1.1. Evolution of reefs during tectonic subsidence according to C. Darwin's
hypothesis: A fringing reef; B barrier reef; C atoll. Facies: 1 basic rocks; 2 consolidated
biogenic carbonate rocks; 3 unconsolidated carbonate rocks
Table 1.1. Thickness of identical reef constructions under modern atolls according to
drilling results; data by Ladd (1969), Purdy (1963)
Basin
Pacific Ocean
Indian Ocean
Caribbean Sea
Atoll
Funafuti
Bikini
Eniwetok
Mururoa
Midway
Maldives
Tenerife
Glower reef
Thickness of
reefal lime
columns, m
>400
>780
1400
>400
2200
1300
1000
Geological age of carbonate
rocks at the base of reef
construction
Quaternary
Tertiary
Jertiary
Quaternary
Quaternary
Eocene
Quaternary
Quaternary
atolls and barrier reefs (Table 1.1, Fig. 1.1). Modern geology relates their
origin to the gradual tectonic subsidence of the whole sea floor together with
the underwater mountains and reefs on their tops situated on it, which was
caused by the movement of corresponding tectonic plates to the oceanic
trenches (Ladd 1969; Scott and Dixon 1983). As we can see, the theory of
Mobilism appeared to be fruitful also in understanding the reef's genesis.
But as regards the origin of the main types of modern reef constructions