Transcript FESD-carbonates-10Feb2012

Global carbonates
Reading list:
Feeley, R.A., Sabine, C.L., Lee, K., Berelson, W., Kleypas J., Fabry, V.J., and Millero,
F.J., 2004, Impact of anthropogenic CO2 on the CaCO3 system in the oceans, Science,
v. 304, pp., 362-366.
Markello, J.R., Koepnick, R.B., Waite, L.E., and Collins, J.F., 2007, The carbonate
analogs through time (CATT) hypothesis and the global atlas of carbonate fields -- a
systematic and predictive look at Phanerozoic carbonate systems, in Controls on
Carbonate Platform and Reef development, SEPM Special Publication no. 89; and chart.
Ridgwell, A. and Zeebe, R.E., 2005, The global carbonate cycle in the regulation and
evolution of the Earth system, Earth and Planetary Science Letters, v. 234, pp. 299-315.
Stanley, S.M., and Hardie, L.A., 1998, Secular oscillations in the carbonate mineralogy
of reef-building and sediment-producing organisms driven by tectonically forced shifts in
seawater chemistry, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 144, pp. 319.
L. Hinnov
February 15, 2012
EARTH’S CARBON RESERVOIRS
Surficial reservoir:
Atmosphere
Oceans
Biosphere
Soils
“Exchangeable sediments”
Geologic reservoir:
Sediments
Crust
Mantle
Cycling between reservoirs:
(a) Precipitation/burial of CaCO3
(b) Weathering/geologic cycling
CARBONATE ENVIRONMENTS
(a) Neritic zone
Shallow marine organisms:
Corals
Benthic shelly animals
Algae
(b) Pelagic zone
Planktonic organisms:
Coccolithophores
Foraminifera
Pteropods (pelagic bivalves)
GLOBAL CARBONATE CYCLE
(a) Surficial to geologic reservoir
1.
2.
3.
4.
Bioprecipitation by pelagic organisms
(calcite)
Carbonate reaching ocean bottom
Bioprecipitation by neritic organisms
(aragonite)
Carbonate precipitation results in
higher pCO2 at surface and CO2 to
atmosphere
(b) Geologic to surficial reservoir
5. Erosion of uplifted carbonate
6. Decarbonation of carbonate (CO2
release in interior)
7. Weathering of silicate rocks (CO2
consumption)
8. CO2 emission from decarbonation
CARBONATE MINERALS
Calcite - a carbonate mineral and the most stable polymorph of calcium
carbonate (CaCO3). Crystal system: Trigonal; specific gravity 2.71g/cm3;
Today is the prevalent mineral precipitated
mainly by pelagic organisms (except pteropods)
QuickTime™ and a
decompressor
are needed to see this picture.
Iceland spar
Aragonite - a carbonate mineral and the second most common calcium
carbonate (CaCO3). Crystal system: Orthorhombic; specific gravity 2.95g/cm3;
Today is a common mineral precipitated
mainly by neritic organisms (also high-Mg
calcite)
QuickTime™ and a
decompressor
are needed to see this picture.
Feeley et al. (2004)
CARBONATE SATURATION STATE OF OCEANS
More older water; more metabolic CO2
Scholle et al., 1983
Lysocline -->  = 0.8
Sea level - e.g., coral reef hypothesis: shelf
flooding, coral reef colonization increased
marine CaCO3 precipitation, caused 70-80
ppm rise in pCO2 during Holocene.
Pelagic calcifiers did not arise until the start
of the Mesozoic Era (250 Ma).
Observed (shaded bars) vs. modeled [Ca2+]
in the world ocean. (Controlled by changes
in mid-ocean ridge volume.)
ARAGONITE v. CALCITE SEAS (next slide)
Deep-sea-carbonate: percent occurrence
of carbonates in ophiolite complexes.
Shallow-marine-carbonate: changes in
the total area of shallow marine
carbonates.
Figure from Ridgwell and Zeebe, 2005
Aragonite
v.
Calcite
Seas
Stanley and
Hardie, 1998
The petroleum geologists perspective:
“Carbonate Analogs Through Time” (CATT):
High-confidence, age-specific predictive models and
concepts for ancient carbonate systems and carbonate
reservoirs in terms of occurrence, composition, stratal
attributes, and reservoir properties can be developed
by summing the ambient conditions of the carbonate
processes and Earth processes at any geologic age.
The summations are termed age-sensitive patterns or
themes. Graphically, the CATT hypothesis can be
expressed as:
Markello et al. (2007)
From left to right:
Markello et al. (2007)