1
The Solid Phase of Marine Sediments
14
small percentage of lithogenic minerals, such as
quartz, feldspar and heavy minerals, confirms the
existence of terrigenous components which in part
should have originated from eolian transport
processes. The biogenic oozes represent the most
frequent type of deep-sea sediments; they mainly
consist of shells and skeletal material from planktonic organisms living in the ocean where they
drizzle from higher photic zones down to the
ocean floor, like continuous rainfall, once they
have died (Fig. 1.6). The fragments of the calcareous-shelled pteropods, foraminifera, and coccolithophorids constitute the calcareous oozes (pteropod ooze, foraminiferal ooze, or nannofossil
ooze), whereas the siliceous radiolarians, silicoflagellates, and diatoms constitute the siliceous
oozes (radiolarian ooze or diatomaceous ooze).
The hemipelagic sediments are basically made
of the same components as the deep-sea red clay
and the biogenic oozes, clay minerals and biogenic particles respectively, but they also contain
an additional and sometimes dominating amount
of terrigenous material, such as quartz, feldspars,
detrital clay minerals, and some reworked biogenous components from the shelves (Table 1.4,
Fig. 1.9).
Most deep-sea sediments can be described according to their composition or origin as a threecomponent system consisting of
(i)
biogenic carbonate,
(ii)
biogenic opal, and
(iii) non-biogenic mineral constituents.
The latter group comprises the components of the
deep-sea red clay and the terrigenous siliciclastics. On the basis of experiences made in the
Deep Sea Drilling Project, Dean et al. (1985) have
Table 1.4 Classification of deep-sea sediments according to Berger (1974).
I. (Eu-)pelagic deposits (oozes and clays)
< 25 % of fraction > 5µm is of terrigenic, volcanogenic, and/or neritic origin
Median grain size < 5µm (except in authigenic minerals and pelagic organisms)
A. Pelagic clays. CaCO 3 and siliceous fossils < 30 %
1. CaCO 3 1 - 10 %. (Slightly) calcareous clay
2. CaCO 3 10 - 30 %. Very calcareous (or marl) clay
3. Siliceous fossils 1 - 10 %. (Slightly) siliceous clay
4. Siliceous fossils 10 - 30 %. Very siliceous clay
B. Oozes. CaCO 3 or siliceous fossils > 30 %
1. CaCO 3 > 30 %. <
2
/ 3 CaCO 3 : marl ooze. >
2 / 3 CaCO 3 : chalk ooze
2. CaCO 3 < 30 %. > 30 % siliceous fossils: diatom or radiolarian ooze
II. Hemipelagic deposits (muds)
> 25 % of fraction > 5 µm is of terrigenic, volcanogenic, and/or neritic origin
Median grain size >5 µm (except in authigenic minerals and pelagic organisms)
A. Calcareous muds. CaCO 3 > 30 %
1. <
2
/ 3 CaCO 3 : marl mud. >
2
/ 3 CaCO 3 : chalk mud
2. Skeletal CaCO 3 > 30 %: foram ~, nanno ~, coquina ~
B. Terrigenous muds, CaCO 3 < 30 %. Quarz, feldspar, mica dominant
Prefixes: quartzose, arkosic, micaceous
C. Volcanogenic muds. CaCO 3 < 30 %. Ash, palagonite, etc., dominant
III. Special pelagic and/or hemipelagic deposits
1. Carbonate-sapropelite cycles (Cretaceous).
2. Black (carbonaceous) clay and mud: sapropelites (e.g., Black Sea)
3. Silicified claystones and mudstones: chert (pre-Neogene)
4. Limestone (pre-Neogene)
The Solid Phase of Marine Sediments
14
small percentage of lithogenic minerals, such as
quartz, feldspar and heavy minerals, confirms the
existence of terrigenous components which in part
should have originated from eolian transport
processes. The biogenic oozes represent the most
frequent type of deep-sea sediments; they mainly
consist of shells and skeletal material from planktonic organisms living in the ocean where they
drizzle from higher photic zones down to the
ocean floor, like continuous rainfall, once they
have died (Fig. 1.6). The fragments of the calcareous-shelled pteropods, foraminifera, and coccolithophorids constitute the calcareous oozes (pteropod ooze, foraminiferal ooze, or nannofossil
ooze), whereas the siliceous radiolarians, silicoflagellates, and diatoms constitute the siliceous
oozes (radiolarian ooze or diatomaceous ooze).
The hemipelagic sediments are basically made
of the same components as the deep-sea red clay
and the biogenic oozes, clay minerals and biogenic particles respectively, but they also contain
an additional and sometimes dominating amount
of terrigenous material, such as quartz, feldspars,
detrital clay minerals, and some reworked biogenous components from the shelves (Table 1.4,
Fig. 1.9).
Most deep-sea sediments can be described according to their composition or origin as a threecomponent system consisting of
(i)
biogenic carbonate,
(ii)
biogenic opal, and
(iii) non-biogenic mineral constituents.
The latter group comprises the components of the
deep-sea red clay and the terrigenous siliciclastics. On the basis of experiences made in the
Deep Sea Drilling Project, Dean et al. (1985) have
Table 1.4 Classification of deep-sea sediments according to Berger (1974).
I. (Eu-)pelagic deposits (oozes and clays)
< 25 % of fraction > 5µm is of terrigenic, volcanogenic, and/or neritic origin
Median grain size < 5µm (except in authigenic minerals and pelagic organisms)
A. Pelagic clays. CaCO 3 and siliceous fossils < 30 %
1. CaCO 3 1 - 10 %. (Slightly) calcareous clay
2. CaCO 3 10 - 30 %. Very calcareous (or marl) clay
3. Siliceous fossils 1 - 10 %. (Slightly) siliceous clay
4. Siliceous fossils 10 - 30 %. Very siliceous clay
B. Oozes. CaCO 3 or siliceous fossils > 30 %
1. CaCO 3 > 30 %. <
2
/ 3 CaCO 3 : marl ooze. >
2 / 3 CaCO 3 : chalk ooze
2. CaCO 3 < 30 %. > 30 % siliceous fossils: diatom or radiolarian ooze
II. Hemipelagic deposits (muds)
> 25 % of fraction > 5 µm is of terrigenic, volcanogenic, and/or neritic origin
Median grain size >5 µm (except in authigenic minerals and pelagic organisms)
A. Calcareous muds. CaCO 3 > 30 %
1. <
2
/ 3 CaCO 3 : marl mud. >
2
/ 3 CaCO 3 : chalk mud
2. Skeletal CaCO 3 > 30 %: foram ~, nanno ~, coquina ~
B. Terrigenous muds, CaCO 3 < 30 %. Quarz, feldspar, mica dominant
Prefixes: quartzose, arkosic, micaceous
C. Volcanogenic muds. CaCO 3 < 30 %. Ash, palagonite, etc., dominant
III. Special pelagic and/or hemipelagic deposits
1. Carbonate-sapropelite cycles (Cretaceous).
2. Black (carbonaceous) clay and mud: sapropelites (e.g., Black Sea)
3. Silicified claystones and mudstones: chert (pre-Neogene)
4. Limestone (pre-Neogene)