Biogenic Sediment Flashcards
how are biogenic sediments classified?
composition
composition of biogenic sediment
hard part remains (calcareous or siliceous) or soft tissue remains (organic carbon)
what makes up calcareous ooze?
coccolithophores, foraminifera, pteropods, snails, clams, corals
coccolithophores
calcareous, phytoplankton (white cliffs of dover, chalk)
planktonic foraminifera
calcareous, zooplankton
benthic foraminifera
calcareous, zooplankton
pteropods
calcareous, zooplankton
gastropods
calcareous, zooplankton, benthic
bivalves
calcareous, zooplankton, benthic
corals
calcareous, benthic
bryozoa
calcareous, benthic
ostracods
calcareous, benthic
sea urchins (spines)
calcareous, benthic
what makes up siliceous ooze?
diatoms, radiolaria, sponge, spicules
diatoms
siliceous, phytoplankton
radiolaria
siliceous, zooplankton
sponges (spicules)
siliceous, benthic
what makes up organic carbon?
dead organic matter, fecal pellets, whale carcasses
calcareous ooze distribution
much delivered to the seafloor everywhere, but not preserved everywhere. near mid ocean ridges, controlled by seawater chemistry
carbonate compensation depth (CCD)
below the CCD, calcium carbonate (CaCO3) dissolves easily due to the seawater’s chemistry.
siliceous ooze distribution
dissolves easily in seawater, need rapid burial for preservation, in high productivity areas and upwelling zones.
organic carbon distribution
rare, transported mostly as fecal pellets and marine snow, decomposes on seabed, never dominates sediments, high productivity, low oxygen areas
photosynthesis and organic carbon
in oxygenated waters, organic carbon is decomposed, and in anoxic waters, organic carbon is preserved
