Reconstructing middle Miocene tectonic boundary conditions Nicholas Herold

Reconstructing middle Miocene tectonic boundary conditions Nicholas Herold, Seton, M. , Müller, R. D. and You. , J. University of Cambridge 11 th August, 2008

This talk. . . Part 1. Reconstructing the oceans Part 2. Reconstructing topography Part 3. Reconstructing middle Miocene palaeogeography – is it worth it? Part 4. Combining palaeogeography with other model boundary conditions

Why the Miocene? Miocene Climatic Optimum (MCO) TIME (Ma) Zachos et al. (2001)

Reconstructing the oceans

Age distribution at 15 Ma

Age converted to depth

Depth error based on age

Sediment thickness Global modern sediment thickness: http: //www. ngdc. noaa. gov/mgg/sedthick. html

Predicted sediment thickness 15 Ma

Large igneous provinces (LIPs) With surrounding seafloor Without surrounding seafloor

Bathymetric reconstruction Age converted depth Age Sediment thickness LIPS

Topography/bathymetry MIOCENE MODERN

Adjustments for climate models Marginal seas Narrow gateways

Mediterranean

Reconstructing Miocene palaeogeography – is it worth it? ?

General Circulation Model NCAR Community Atmosphere Model and Community Land Model. ~3. 75° x 3. 75° horizontal resolution, 26 atmospheric layers. atm lnd cpl ocn ice

Combining palaeogeography with other boundary conditions Other boundary conditions - Greenhouse gases - Orbital parameters - Solar constant - River Transport

Mean annual surface temperature

Model-data temperature discrepancies Mean discrepancy: -1. 7°C

Model-data precipitation discrepancies Mean discrepancy: -172 mm/year

In summary New Miocene palaeogeography. Preliminary results of a Miocene climate simulation: too cool and arid compared to proxy data. Need to run coupled climate simulations using new palaeogeography in order to better resolve and understand proxy-model discrepancies.

Thanks. . . Müller, R. D. , Sdrolias, M. , Gaina, C. and Roest, W. R. , 2008. Age, spreading rates and spreading asymmetry of the world's ocean crust. Geochemistry, Geophysics, Geosystems. : Q 04006. Müller, R. D. , Sdrolias, M. , Gaina C. , Steinberger B. and C. , H. , 2008. Long-Term Sea-Level Fluctuations Driven by Ocean Basin Dynamics. Science, 319(5868): 1357 -1362.

Kearey and Vine, 1996

Annual zonal mean sea surface temperature

References Stampfli, G. M. and Borel, G. D. , 2002. A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons. Earth and Planetary Science Letters, 196(1 -2): 17 -33.