| Title: | Quantifying Precipitation Flux Changes of the mid-Cretaceous (Albian) Greenhouse World: Isotope Mass Balance Approach Constrained by Sphaerosiderite Oxygen Isotope Composition |
| Author: | Luis A Gonzalez |
| Date Submitted: | 05/02/2002 |
| Address: | 121 TH
Dept. of Geoscience
Iowa City
Iowa
USA
52242-1379
|
| Phone: | 319-335-0567 |
| Email: | luis-gonzalez@uiowa.edu |
| Co-Authors: | Ludvigson, Greg, A., U. Iowa, Geoscience, gregory-ludvigson@uiowa.edu; Ufnar, David, F., U. Iowa, Geoscience, dufnar@cadet.com; Brenner, Robert, L., U. Iowa, Geoscience, robert-brenner@uiowa.edu; Witzke, Brian, J., U. Iowa, Geoscience, brian-witzke@uiowa |
| Affiliation: | The University of Iowa |
| | |
| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725620 |
| Author Homepage: | http://www2.uiowa.edu/~lgonzlez/ |
| Author Project webpage: | http://www2.uiowa.edu/~lgonzlez/#Cretaceous |
| Keywords: | Albian, 18O, hydrologic cycle, mid-Cretaceous, precipitation WIB |
| Abstract: | Spherulitic siderites are ubiquitous in ancient
hydric/wetland paleosols that are widespread over
coastal plains of the North American Cretaceous
Western Interior Basin (KWIB). The oxygen isotopic of
sphaerosiderite records that of paleogroundwaters,
and thus serves as a proxy of precipitation oxygen
isotopic composition.
Albian sphaerosiderites sampled from paleosols along
the coastal plains of the KWIB exhibit a progressive
depletion in oxygen isotopic composition from - 4 per
mil at 34° N to -16 per mil at 75° N paleolatitude. The
sphaerosiderite oxygen isotope composition has been
used to constrain an isotope mass balance model of
precipitation isotope composition and to quantify
precipitation and evaporation fluxes along the KWIB.
Our modeling indicates that Albian precipitation fluxes
were 38 to 53 % higher than present day fluxes.
Likewise, evaporation fluxes are estimated to be 76 to
96 % higher than present day fluxes. While humid belts
are wetter, the dry belts are drier. Precipitation rates
exceeded 3500 mm/yr between 45° to 60° N
paleolatitude, and could have been as high as 6000
mm/yr at 55° N.
Our estimates are consistent with geologic evidence
such as the widespread distribution at high latitudes of
paleosols that require high precipitation rates (e.g.,
laterites, ferralsols, plinthosols); extensive boulder to
gravel conglomerates deposits in the Dakota
Formation in Iowa and Nebraska; and widespread coal
deposits at high latitudes.
Our model results differ from climate model results
(e.g. GENESIS) in that equatorial precipitation rates are
lower than those estimated by climate models, while
mid to high latitude estimates are significantly higher
and of equal or larger magnitude than those modeled
for equatorial regions. Our estimates imply that
atmospheric heat transport must have been
significantly higher during the mid-Cretaceous (Albian)
and can account for "missing" poleward heat transport
during the mid-Cretaceous. |
|