L. HinnovFebruary 15, 2012

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. 3-19.

Surficial reservoir:

Geologic reservoir:

AtmosphereOceansBiosphereSoils“Exchangeable sediments”

SedimentsCrustMantle

EARTH’S CARBON RESERVOIRS

Cycling between reservoirs:

(a) Precipitation/burial of CaCO3

(b) Weathering/geologic cycling

CARBONATE ENVIRONMENTS

(b) Pelagic zone

(a) Neritic zone

Shallow marine organisms:CoralsBenthic shelly animalsAlgae

Planktonic organisms:CoccolithophoresForaminiferaPteropods (pelagic bivalves)

(a) Surficial to geologic reservoir

(b) Geologic to surficial reservoir

1. Bioprecipitation by pelagic organisms (calcite)

2. Carbonate reaching ocean bottom3. Bioprecipitation by neritic organisms

(aragonite)4. Carbonate precipitation results in

higher pCO2 at surface and CO2 to atmosphere

5. Erosion of uplifted carbonate6. Decarbonation of carbonate (CO2 release in interior)7. Weathering of silicate rocks (CO2 consumption) 8. CO2 emission from decarbonation

GLOBAL CARBONATE CYCLE

Calcite - a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). Crystal system: Trigonal; specific gravity 2.71g/cm3;

Aragonite - a carbonate mineral and the second most common calcium carbonate (CaCO3). Crystal system: Orthorhombic; specific gravity 2.95g/cm3;

CARBONATE MINERALS

Today is the prevalent mineral precipitated mainly by pelagic organisms (except pteropods)

Today is a common mineral precipitated mainly by neritic organisms (also high-Mg calcite)

QuickTime™ and a decompressor

are needed to see this picture.

Iceland spar

QuickTime™ and a decompressor

are needed to see this picture.

Feeley et al. (2004)

Scholle et al., 1983

CARBONATE SATURATION STATE OF OCEANS

Lysocline --> = 0.8More older water; more metabolic CO2

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

Aragonitev.

CalciteSeas

Stanley and Hardie, 1998

Markello et al. (2007)

“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:

The petroleum geologists perspective:

Markello et al. (2007)

From left to right: