Upper Mantle Dynamics and
Quaternary Climate in Cratonic Areas
International Lithosphere Program (ILP) Regional Co-ordination
Committee CC
1/5
Our present knowledge of the rheology of the lower crust is based mostly on petrophysical inference from seismology and heat flow (Blundell et al., 1992). Continuous GPS observations of plate-wide strain, accompanied by seismological investigations, and followed by continuum mechanical modelling of GIA, seismic source and wave propagation, and studies of the post-glacial faults offer a new entry and will add new insights into the role and properties of the lower crust. Observations and models of post-glacial or glacially induced faulting can help to illuminate crustal stress fields and therefore crustal rheology issues. On the lithosphere-mantle scale we expect, mostly on the basis of on-going improvements and densifications of GPS observations, that the fully 3-D observations, augmented by gravity (GRACE and GOCE) and sea level change. Drawing from advances in thermodynamical and climatological ice sheet modelling will retrieve laterally heterogeneous structure of mantle and lithosphere from the observed motions.
Existing data on experimentally studied lower crustal and mantle
composition and 3-D structure derived from xenolith data, lithospheric
thermal models and seismic studies should be utilized for
forward rheological modelling of the lithosphere and for testing of
dynamic uplift models. The presence and volume of fluids in the upper
mantle and the influence of fluids on the mantle rheology is an open
question. As dissociated water may provide an effective mechanism for
electrical conductivity in the upper mantle, important implications on
mantle fluids and lithosphere-asthenosphere system in general can be
potentially obtained from recent deep electromagnetic measurements.