172
of the trade wind-driven South Equatorial Current
which enters the basin in the southeast through the
Lesser Antilles Islands. The outflow of Caribbean
water takes place in the northwest through the southeastern Gulf of Mexico and the Straits of Florida
(Gordon 1966). Surface water temperatures are high
throughout the year (25 to 28°C), and salinities are
slightly above average (34 to 36.5%0). Such conditions, in conjunction with limited nutrient supply,
enable optimal coral reef growth. During glacial periods, the water temperature was slightly lower (1 to
3°C). The Pliocene and Quaternary pelagic sediments
are predominantly nannoplankton-foraminiferal
oozes, reflecting the high temperature and lirnited
nutrient content of the surface waters.
The shape and extent of carbonate shelves associated with
the Caribbean islands and coral reefs are, among other factors, influenced by the wind pattern and surface current
system (Adey and Burke 1977; Geister 1983). The shelf off
west Florida and the platforms of Florida and Campeche
represent outstanding examples of a carbonate province.
In contrast to the Red Sea, the water rnasses of the Caribbean are distinctly stratified due to the wide connection
to the Atlantic. The Caribbean deep water has therefore a
much lower temperature and is less saline than its surface
water. It is weil oxygenated in the deep Colombian and
Venezuelan basins, but oxygen-poor in a small area in the
southeast (Cariaco Trench). The modern deep-sea sediments ofthis region, however, exhibit no c1ear relationship
with the separated inflow and outflow of surface currents.
This may result from the topographic and tectonic complexity of the Caribbean Sea and its transition into the G~lf
of Mexico (Naim and Stehli 1975). As long as a seaway
existed between the Caribbean Sea and the eastern Pacific
(prior to about 5 Ma B.P.), ocean circulation and sediments
of the Caribbean differed significantly from the present
situation (cf. Sect. 5.6).
Older sediment cores recovered in the Caribbean sea by
the Ocean Drilling Program record other events of global
importance (Shipboard Scientific Party, ODP Leg 165,
1997), e.g. ejecta from a meteorite impact at the Cretaceous/Tertiary boundary, evidence for a global thermal
maximum in the late Paleocene, a Miocene minimum in
carbonate accumulation ("carbonate-crash"), a well-Iaminated sequence in the euxinic Cariaco Basin, and high explosive volcanic activity in the Eocene and Miocene.
The western part of the Gulf of Mexico and the Colombian basin (western Caribbean Sea) receive large
amounts of terrigenous material delivered by major
rivers, as weIl as volcanic1astics from different
sources within the area. These sediments build delta
cones and deep-sea fans, inc1uding turbidites, and
dilute the biogenic sediment production in various
ways.
The Norwegian-Greenland Sea. This sea represents
the northern N orth Atlantic and forms a subpolar
deep-sea basin to the north of the Greenland-IcelandFaeroe-Scotland Ridge (Fig. 4.3c). In conjunction
with the Arctic seas, the Norwegian-Greenland Sea is
Chapter 4 Adjacent Seas
surrounded on all sides by land masses and largely
separated by submarine sills from the deep-water
circulation of the world oceans. At present, the Arctic seas are perrnanently or seasonally coverd by ice.
On the eastern side of the Norwegian-Greenland sea, the
present-day Norwegian surface current is relatively warm
(4 to 13°C, salinity about 35%0). It originates from the
northern branch ofthe GulfStream, which flows northward
and transports heat and nutrient-poor water masses into the
northern ocean (e.g. Thiede et al. 1986). After substantial
heat transfer to the atrnosphere, the cold and relatively
dense surface water forms downwelling water masses
which flow southward and contribute to the deep-ocean
ventilation. In contrast, the outflowing surface current (the
East Greenland Current) is cold (-1.5 to +2°C) and less
saline (31 to 34%0). It is partly fed by waters entering via
the Fram Strait (between Greenland and Svalbard; Fig.
4.3c) from the Arctic Ocean.
The depositiona1 environment of the NorwegianGreenland Sea is markedly aSyllnnetric as a result of
basin morphology and water circulation. The sediments below the Gulf Stream (Norwegian Current)
tend to be relatively rich in biogenic carbonate, although terrestrial material generally dominates in this
basin. The cold East Greenland Current is richer in
nutrients than the Norwegian Current and enab1es a
relatively high production of siliceous phytoplankton
(diatoms ) during the warmer season and thus the deposition of sediments rich in bio genie silica
(Bohrmann 1988). In addition, the East Greenland
Current carries ice-rafted materials southward. At
present, the deep waters of the entire basin have high
oxygen contents.
The depositional environment of the high-latitude
oceans experienced great variations in temperature
and other characteristics in the geological past, particularly during the Cenozoic. These changes are recorded in the marine sediments explored by ocean
drilling (cf. Sect. 5.6).
4.2.6 Estuarine and Anti-Estuarine
Large Ocean Basins
FinaUy, the terms "estuarine and anti-estuarine circulation" can also be applied to large ocean basins
(Berger 1970, 1976) which exchange their water
masses. For example, the present-day Atlantic Ocean
exhibits deep-water outflow into the Pacific and thus
anti-estuarine circulation (cf. Sect. 5.6). Consequently, the Atlantic tends to accumulate more carbonate and less si1ica than the Pacific, which in turn
exhibits higher ferti1ity, especially for bio genie silica,
and increased carbonate dissolution. Generally, oceanic basins with estuarine circulation tend to develop
stagnant bottom waters and to accumulate anaerobic
sediments. Another consequence of slow inter-oceanic water exchange is the fact that, for example,
of the trade wind-driven South Equatorial Current
which enters the basin in the southeast through the
Lesser Antilles Islands. The outflow of Caribbean
water takes place in the northwest through the southeastern Gulf of Mexico and the Straits of Florida
(Gordon 1966). Surface water temperatures are high
throughout the year (25 to 28°C), and salinities are
slightly above average (34 to 36.5%0). Such conditions, in conjunction with limited nutrient supply,
enable optimal coral reef growth. During glacial periods, the water temperature was slightly lower (1 to
3°C). The Pliocene and Quaternary pelagic sediments
are predominantly nannoplankton-foraminiferal
oozes, reflecting the high temperature and lirnited
nutrient content of the surface waters.
The shape and extent of carbonate shelves associated with
the Caribbean islands and coral reefs are, among other factors, influenced by the wind pattern and surface current
system (Adey and Burke 1977; Geister 1983). The shelf off
west Florida and the platforms of Florida and Campeche
represent outstanding examples of a carbonate province.
In contrast to the Red Sea, the water rnasses of the Caribbean are distinctly stratified due to the wide connection
to the Atlantic. The Caribbean deep water has therefore a
much lower temperature and is less saline than its surface
water. It is weil oxygenated in the deep Colombian and
Venezuelan basins, but oxygen-poor in a small area in the
southeast (Cariaco Trench). The modern deep-sea sediments ofthis region, however, exhibit no c1ear relationship
with the separated inflow and outflow of surface currents.
This may result from the topographic and tectonic complexity of the Caribbean Sea and its transition into the G~lf
of Mexico (Naim and Stehli 1975). As long as a seaway
existed between the Caribbean Sea and the eastern Pacific
(prior to about 5 Ma B.P.), ocean circulation and sediments
of the Caribbean differed significantly from the present
situation (cf. Sect. 5.6).
Older sediment cores recovered in the Caribbean sea by
the Ocean Drilling Program record other events of global
importance (Shipboard Scientific Party, ODP Leg 165,
1997), e.g. ejecta from a meteorite impact at the Cretaceous/Tertiary boundary, evidence for a global thermal
maximum in the late Paleocene, a Miocene minimum in
carbonate accumulation ("carbonate-crash"), a well-Iaminated sequence in the euxinic Cariaco Basin, and high explosive volcanic activity in the Eocene and Miocene.
The western part of the Gulf of Mexico and the Colombian basin (western Caribbean Sea) receive large
amounts of terrigenous material delivered by major
rivers, as weIl as volcanic1astics from different
sources within the area. These sediments build delta
cones and deep-sea fans, inc1uding turbidites, and
dilute the biogenic sediment production in various
ways.
The Norwegian-Greenland Sea. This sea represents
the northern N orth Atlantic and forms a subpolar
deep-sea basin to the north of the Greenland-IcelandFaeroe-Scotland Ridge (Fig. 4.3c). In conjunction
with the Arctic seas, the Norwegian-Greenland Sea is
Chapter 4 Adjacent Seas
surrounded on all sides by land masses and largely
separated by submarine sills from the deep-water
circulation of the world oceans. At present, the Arctic seas are perrnanently or seasonally coverd by ice.
On the eastern side of the Norwegian-Greenland sea, the
present-day Norwegian surface current is relatively warm
(4 to 13°C, salinity about 35%0). It originates from the
northern branch ofthe GulfStream, which flows northward
and transports heat and nutrient-poor water masses into the
northern ocean (e.g. Thiede et al. 1986). After substantial
heat transfer to the atrnosphere, the cold and relatively
dense surface water forms downwelling water masses
which flow southward and contribute to the deep-ocean
ventilation. In contrast, the outflowing surface current (the
East Greenland Current) is cold (-1.5 to +2°C) and less
saline (31 to 34%0). It is partly fed by waters entering via
the Fram Strait (between Greenland and Svalbard; Fig.
4.3c) from the Arctic Ocean.
The depositiona1 environment of the NorwegianGreenland Sea is markedly aSyllnnetric as a result of
basin morphology and water circulation. The sediments below the Gulf Stream (Norwegian Current)
tend to be relatively rich in biogenic carbonate, although terrestrial material generally dominates in this
basin. The cold East Greenland Current is richer in
nutrients than the Norwegian Current and enab1es a
relatively high production of siliceous phytoplankton
(diatoms ) during the warmer season and thus the deposition of sediments rich in bio genie silica
(Bohrmann 1988). In addition, the East Greenland
Current carries ice-rafted materials southward. At
present, the deep waters of the entire basin have high
oxygen contents.
The depositional environment of the high-latitude
oceans experienced great variations in temperature
and other characteristics in the geological past, particularly during the Cenozoic. These changes are recorded in the marine sediments explored by ocean
drilling (cf. Sect. 5.6).
4.2.6 Estuarine and Anti-Estuarine
Large Ocean Basins
FinaUy, the terms "estuarine and anti-estuarine circulation" can also be applied to large ocean basins
(Berger 1970, 1976) which exchange their water
masses. For example, the present-day Atlantic Ocean
exhibits deep-water outflow into the Pacific and thus
anti-estuarine circulation (cf. Sect. 5.6). Consequently, the Atlantic tends to accumulate more carbonate and less si1ica than the Pacific, which in turn
exhibits higher ferti1ity, especially for bio genie silica,
and increased carbonate dissolution. Generally, oceanic basins with estuarine circulation tend to develop
stagnant bottom waters and to accumulate anaerobic
sediments. Another consequence of slow inter-oceanic water exchange is the fact that, for example,