Geology Reference
In-Depth Information
Fig. 2.7.
Generalized subdivision of carbonate ramps. Compare with Box 2.4.
Moore 1983). Carbonate shelf-slope breaks are station-
ary, offlap or onlap. Many carbonate shelf and ramp
margins are characterized by reefs or by sand banks
(Wilson 1974; Halley et al. 1983; James and Mountjoy
1983) which are the line source provenance of most
deep-water resedimented carbonates (Schlager and
Chermak 1979). Platform margins are subdivided into
depositional margins, by-pass margins and rimmed
margins. Depending on the geometry of the shelf mar-
gin and the declivity of the slopes, depositional and
by-pass margins and slopes can be differentiated. Depo-
sitional margins exhibit a low relief from platform to
slope and basins; by-pass margins are characterized
by a steeper relief triggering the deposition of most
platform-derived sediment on lower slopes, toe-of-
slopes and in adjacent basin plains. For the recogni-
tion of margin types with microfacies see Sect. 15.7.
perate and cold waters has been increasing (see Sect.
16.4). Reefal carbonate production is generally con-
sidered as an essential factor in the formation of car-
bonate platforms (Bosscher and Schlager 1993; Kleypas
1997), but this opinion has recently been questioned
(Kiessling et al. 2000).
Reefs and their eminent role in the development of
carbonate depositional systems are discussed in Chap.
14. Box 2.5 contains a glossary of some of the (too)
many terms used in the context of reef studies.
Basics: Modern shallowmarine carbonate environments
Ahr, W.M. (1973): The carbonate ramp: an alternative to
the shelf model. - Transact. Gulf Coast Ass. Geol. Soc.,
23
, 221-225
Ahr, W.M. (1998): Carbonate ramps, 1973-1996: a historical
review. - In: Wright, V.P., Burchette, T.P. (eds.): Carbon-
ate ramps. - Geol. Soc. London Spec. Publ.,
149
, 7-14
Burchette, T.P., Wright, V.P. (1992): Carbonate ramp deposi-
tional systems. - Sed. Geol.,
79
, 3-57
Crevello, P.D., Wilson, J.L., Sarg, J.F., Read, J.F. (eds., 1989):
Controls on carbonate platform and basin development. -
Soc. Econ. Paleont. Min. Spec. Publ.,
44
, 405 pp.
Enos, P. (1983): Shelf environment. - In: Scholle, P.A., Be-
bout, D.G., Moore, C.H. (eds.): Carbonate depositional
environments. - Amer. Ass. Petrol. Geol. Mem.,
33
, 267-
296
Halley, R.B., Harris, P.M., Hines, A.C. (1983): Bank margin
environment. - In: Scholle, P.A., Bebout, D.G., Moore,
C.H. (eds.): Carbonate depositional environments. - Amer.
Ass. Petrol. Geol. Mem.,
33
, 463-506
Harris, P.M., Moore, C.H., Wilson, J.L. (1985): Carbonate
depositional environments. Modern and ancient. Part 2:
Carbonate platforms. - Colorado School of Mines Quart.,
80
, 1-60
2.4.3.4 Reefs
Reefs are singled out from the broad spectrum of ma-
rine environments because of the dominating role of
benthic organisms in the formation of these structures.
Modern reefs originate predominantly in shallow-ma-
rine environments,but are also formed in deeper posi-
tions on the slope and even in basins. Contradictory
long-held opinions that reefs are more or less confined
to tropical and subtropical, low-latitude warm-water
zones and the new knowledge that modern and ancient
reefs can also be formed in mid- and high-latitude tem-
