9
needles (few micrometers) within the more or less
concentric layers of calcareous ooids have been
considered for a long time as primary precipitates
from seawater. However, further investigations including the distribution of stable isotopes distinctly evidenced their biological origin as products of calcification by unicellular algae. Yet, one
part of the acicular aragonite ooze might still originate from the mechanical disruption of shells and
skeletal elements.
Although marine plants and animals are numerous and diverse, only relatively few groups produce hard parts capable of contributing to the
formation of sediments, and only very few groups
occur in an abundance relevant for sediment formation (Table 1.2). Relevant for sediment formation are only carbonate minerals in the form of aragonite, Mg-calcite and calcite, as well as biogenic
opal in the form of amorphous SiO 2 ·nH 2 O. The
sulfates of strontium and barium as well as
various compounds of iron, manganese, and aluminum are of secondary importance, yet they are
of geochemical interest, e.g. as tracers for the reconstruction of past environmental conditions.
For example, the phosphatic particles formed by
various organisms, such as teeth, bone, and shells
of crustaceans, are major components of phosphorite rocks which permit us to draw conclusions
about nutrient cycles in the ocean.
Large amounts of carbonate sediment accumulate on the relatively small surface of the shallow
shelf seas – as compared to entire oceans surface
– of the tropical and subtropical warm water regions, primarily by few lime-secreting benthic
macrofossil groups. Scleritic corals, living in symbiosis with algae, and encrusting red algae consti1.2
Sources and Components of Marine Sediments
Aragonite Aragonite Mg-Calcite Calcite
Calcite +
Opal
divers
+ Calcite
Mg-Calcite
Plankton
Pteropods
x
Radiolarians
x
celestite
Foraminifera
(x)
x
x
x
Coccolithophores
x
Dinoflagellates
x
organic
Silicoflagellates
x
Diatoms
x
Benthos
Chlorophyta
x
Rhodophyta
x
x
(x)
Phaeophyta
x
Sponges
x
x
x
celestite
Scleratinian corals
x
Octocorals
x
x
Bryozoens
x
x
Brachiopods
x
phosphate
Gastropods
x
x
Pelecypods
x
x
x
Decapods
x
phosphate
Ostracods
(x)
x
Barnacles
(x)
x
Annelid worms
x
x
x
(x)
phosphate
Echinoderms
x
phosphate
Ascidians
x
Table 1.2 Major groups of marine organisms contributing to biogenic sediment formation and mineralogy of skeletal
hard parts. Foraminifera and diatoms (underlined) are important groups of both plankton and benthos. x = common,
(x) = rare (mainly after Flügel 1978, 2004 and Milliman 1974).
needles (few micrometers) within the more or less
concentric layers of calcareous ooids have been
considered for a long time as primary precipitates
from seawater. However, further investigations including the distribution of stable isotopes distinctly evidenced their biological origin as products of calcification by unicellular algae. Yet, one
part of the acicular aragonite ooze might still originate from the mechanical disruption of shells and
skeletal elements.
Although marine plants and animals are numerous and diverse, only relatively few groups produce hard parts capable of contributing to the
formation of sediments, and only very few groups
occur in an abundance relevant for sediment formation (Table 1.2). Relevant for sediment formation are only carbonate minerals in the form of aragonite, Mg-calcite and calcite, as well as biogenic
opal in the form of amorphous SiO 2 ·nH 2 O. The
sulfates of strontium and barium as well as
various compounds of iron, manganese, and aluminum are of secondary importance, yet they are
of geochemical interest, e.g. as tracers for the reconstruction of past environmental conditions.
For example, the phosphatic particles formed by
various organisms, such as teeth, bone, and shells
of crustaceans, are major components of phosphorite rocks which permit us to draw conclusions
about nutrient cycles in the ocean.
Large amounts of carbonate sediment accumulate on the relatively small surface of the shallow
shelf seas – as compared to entire oceans surface
– of the tropical and subtropical warm water regions, primarily by few lime-secreting benthic
macrofossil groups. Scleritic corals, living in symbiosis with algae, and encrusting red algae consti1.2
Sources and Components of Marine Sediments
Aragonite Aragonite Mg-Calcite Calcite
Calcite +
Opal
divers
+ Calcite
Mg-Calcite
Plankton
Pteropods
x
Radiolarians
x
celestite
Foraminifera
(x)
x
x
x
Coccolithophores
x
Dinoflagellates
x
organic
Silicoflagellates
x
Diatoms
x
Benthos
Chlorophyta
x
Rhodophyta
x
x
(x)
Phaeophyta
x
Sponges
x
x
x
celestite
Scleratinian corals
x
Octocorals
x
x
Bryozoens
x
x
Brachiopods
x
phosphate
Gastropods
x
x
Pelecypods
x
x
x
Decapods
x
phosphate
Ostracods
(x)
x
Barnacles
(x)
x
Annelid worms
x
x
x
(x)
phosphate
Echinoderms
x
phosphate
Ascidians
x
Table 1.2 Major groups of marine organisms contributing to biogenic sediment formation and mineralogy of skeletal
hard parts. Foraminifera and diatoms (underlined) are important groups of both plankton and benthos. x = common,
(x) = rare (mainly after Flügel 1978, 2004 and Milliman 1974).