Cretaceous carbonate platforms:
stratigraphy, rudist, and Earth's systems science.
 Dr. Thomas Steuber
  
 
  • Cretaceous rudist bivalves
  • Interactions between Cretaceous carbonate platform systems, seawater composition and paleoclimate
  • Strontium-isotope stratigraphy of Cretaceous
Cretaceous rudist bivalves

Rudists are among the most important carbonate producers on mid- and Upper Cretaceous carbonate platforms. Rudist lithosomes form some of the prolific reservoirs in the Middle East, and thus paleoecology, taxonomy and biostratigraphy of the group are important for the interpretation of facies, regional correlation, and prediction of reservoir architecture. Current research is focused on the paleontology and stratigraphy of the Campanian-Maastrichtian rudists of the UAE.

Data on rudist paleontology, stratigraphy and paleobiology can be found at http://www.ruhr-uni-bochum.de/sediment/rudinet/intro.htm. References
  • Steuber, T. and Löser, H. (2000): Species richness and abundance patterns of Tethyan Cretaceous rudist bivalves (Mollusca: Hippuritacea) in the central-eastern Mediterranean and Middle East, analysed from a palaeontological data base. Palaeogeography, Palaeoclimatology, Palaeoecology, v. 162, p. 75-104.
  • Steuber, T. (2000) Skeletal growth rates of Upper Cretaceous rudist bivalves: implications for carbonate production and organism – environment feedbacks. in: Insalaco, E., Skelton, P.W. and Palmer, T.J. (Eds.), Carbonate Platform Systems: Components and Interactions, Geological Society Special Publication, v. 178, p. 21-32.
  • Steuber, T. (2002) A palaeontological database of rudist bivalves.- http://www.ruhr-uni-bochum.de/sediment/rudinet/intro.htm.
  • Steuber, T. (2003) Strontium isotope stratigraphy of Cretaceous hippuritid rudist bivalves: rates of morphological change and heterochronic evolution. Palaeogeography, Palaeoclimatology, Palaeoecology, v. 200, p. 221-243.
    also: Virtual Journal of Geobiology, 2 (November 2003).
     
Interactions between Cretaceous carbonate platform systems, seawater composition and paleoclimate

There is increasing evidence that the major-ion composition of Cretaceous seawater was significantly different from that of modern oceans. Seawater composition affected platform carbonate sedimentation. In the mid-Cretaceous, there was change from aragonite-dominated coral-algal communities to calcite-dominated rudist bivalves as the main carbonate producers. The change is explained as a response to a low Mg/Ca ratio of mid-Cretaceous seawater. In turn, the ecologic shift among the major carbonate producers is reflected in the Sr/Ca ratio of Cretaceous seawater, because aragonite sedimentation is a major sink for Sr. Consequently, the Sr/Ca ratio of seawater rose in the Late Cretaceous, when marine carbonate sedimentation was predominantly calcite. Most of the data which support this hypothesis are derived from the shells of Cretaceous rudist bivalves because well preserved specimens still contain geochemical information about the major-ion composition of the seawater the animals lived in. Rudist fossils are also important archives for Cretaceous sea-surface paleotemperatures and their seasonality. For the late part of the Early Cretaceous (Barremian-Albian) the latitude-dependent seasonality patterns of paleotemperature are very similar to today, suggesting the presence of polar ice caps. The Cretaceous greenhouse episode with temperatures much higher than today is reflected in the seasonality pattern of Late Cretaceous samples.

 

 

Phanerozoic seawater Sr/Ca ratios, and episodes of calcite or aragonite-dominated carbonate sedimentation (from Steuber and Veizer, 2002).









Mg/Ca ratio of Cretaceous seawater as derived from rudist shells (red and blue symbols), from fluid inclusions in halite, and from geochemical model simulations (Steuber and Rauch, 2005).


Sea-surface paleotemperature seasonality at low northern paleolatitude during Late Cretaceous greenhouse conditions (Late Albian – Campanian, left) and early Cretaceous cooler episode (Barremian-Middle Albian, right) compared to modern seasonal ranges (colored areas). Data are derived from rudist shells (Steuber et al., 2005).


References
  • Steuber, T. (2002) Plate tectonic control on the evolution of Cretaceous platform-carbonate production. Geology, v. 30, p. 259-262.
  • Steuber, T. and Veizer, J. (2002) Phanerozoic record of plate tectonic control of seawater chemistry and carbonate sedimentation. Geology, v. 30, p. 1123-1126.
  • Steuber, T., Rauch, M., Masse, J.-P., Graaf, J. and Malkoč, M. (2005) Low-latitude seasonality of Cretaceous temperatures in warm and cold episodes. Nature, v. 437, p. 1341-1344.
  • Steuber, T. and Rauch, M. (2005) Evolution of the Mg/Ca ratio of Cretaceous seawater - Implications from the composition of biological low-Mg calcite. Marine Geology, v. 217, p. 199-213.
  • Steuber, T. and Buhl, D. (in press) Calcium-isotope fractionation in modern and ancient marine carbonates. Geochimica et Cosmochimica Acta
  • Yan, J., Munnecke, A., Steuber, T., Carlson, E.H. and Xiao, Y. (2005) Marine sepiolite in middle Permian carbonates of South China: Implications for secular variations in Phanerozoic seawater chemistry. Journal of Sedimentary Research, v. 75, p. 328-338.
     
Strontium-isotope stratigraphy of Cretaceous carbonate platforms



Late Cretaceous paleogeography and localities studied		 The changing Sr-isotope ratio of Cretaceous seawater is well calibrated to chronostratigraphy. Consequently, numerical ages can be derived from skeletal carbonate that have preserved the original seawater Sr-isotope ratio. This allows for global stratigraphic correlation independent of lithofacies. The method has proven particularly useful in Cretaceous shallow water carbonates, where biostratigraphical correlation can be difficult, and the time-transgressive nature of lithostratigraphical units (e.g., prograding carbonate platforms) may not be obvious from conventional stratigraphy. Current research is externally funded and focuses on the Campanian-Maastrichtian of the Arabian Plate, including the Qahlah and Simsima Formations of the UAE.
 






Quantification of platform progradation with numerical ages of boundaries of lithostratigraphic units derived from strontium isotope stratigraphy. Island of Brac, Adriatic carbonate platform (Steuber et al., 2005).

References
  • Immenhauser, A., Hillgärtner, H., Sattler, U., Bertotti, G., Schoepfer, P., Homewood, P., Vahrenkamp, V., Steuber, T. and 11 others (2004) The Barremian - Lower Aptian Qishn Formation (Huqf area, Oman): an outcrop analogue for Kharaib/Shu'aiba subsurface reservoirs. GeoArabia, v. 9, p. 153-194.
  • Steuber, T. (2003) Strontium isotope chemostratigraphy of rudist bivalves and Cretaceous carbonate platforms. in: Gili, E., Negra, M.H. and Skelton, P.W. (Eds.), North African Cretaceous carbonate platform systems, NATO Science Series, Earth and Environmental Sciences, v. 28, p. 229-238
  • Steuber, T., Korbar, T., Jelaska, V. and Gušić, I. (2005) Strontium – isotope stratigraphy of Upper Cretaceous platform carbonates of the Island of Brač (Adriatic Sea, Croatia) - Implications for global correlation of platform evolution and biochronostratigraphy. Cretaceous Research, v. 26, p. 741-756.
  • Steuber, T., Parente, M., Hagmaier, M., Immenhauser, A. van der Kooij, B. and Frija, G. (in press): Latest Maastrichtian species-rich rudist associations of the Apulian margin of Salento (S Italy) and the Ionian Islands (Greece). Society for Sedimentary Geology (SEPM), Special Publication.