We present a new analysis of the lithospheric architecture of Africa, and its evolution from ca. 3.6 Ga to the present. Upperlithosphere domains, generated or reworked in different time periods, have been delineated by integrating regional tectonics and geochronology with geophysical data (magnetic, gravity, and seismic). The origins and evolution of lower-lithosphere domains are interpreted from a high-resolution global shear-wave tomographic model, using thermal/compositional modeling and xenolith/ xenocryst data from volcanic rocks. These data are integrated to map the distribution of Begg et al. 24 Geosphere, February 2009 only the latest stage in this process. The less depleted SCLM that underlies some accretionary belts may have been generated in Archean time, and repeatedly refertilized by the passage of magmas during younger tectonic events. Our analysis indicates that originally Archean SCLM is far more extensive beneath Africa than previously recognized, and implies that post-Archean SCLM rarely survives the collision/accretion process. Where continental crust and SCLM have remained connected, there is a strong linkage between the tectonic evolution of the crust and the composition and modifi cation of its underlying SCLM.

Multibeam swath bathymetry and sub‐bottom profiler data are used to establish constraints on the flow and retreat history of a major palaeo‐ice stream that carried the combined discharge from the parts of the West Antarctic Ice Sheet now occupied by the Pine Island and Thwaites glacier basins. Sets of highly elongated bedforms show that, at the last glacial maximum, the route of the Pine Island‐Thwaites palaeo‐ice stream arced north‐northeast following a prominent cross‐shelf trough. In this area, the grounding line advanced to within ∼68 km of, and probably reached, the shelf edge. Minimum ice thickness is estimated at 715 m on the outer shelf, and we estimate a minimum ice discharge of ∼108 km3 yr−1 assuming velocities similar to today's Pine Island glacier (∼2.5 km yr−1). Additional bed forms observed in a trough northwest of Pine Island Bay likely formed via diachronous ice flows across the outer shelf and demonstrate switching ice stream behavior. The “style” of ice retreat is also evident in five grounding zone wedges, which suggest episodic deglaciation characterized by halts in grounding line migration up‐trough. Stillstands occurred in association with changes in ice bed gradient, and phases of inferred rapid retreat correlate to higher bed slopes, supporting theoretical studies that show bed geometry as a control on ice margin recession. However, estimates that individual wedges could have formed within several centuries still imply a relatively rapid overall retreat. Our findings show that the ice stream channeled a substantial fraction of West Antarctica's discharge in the past, just as the Pine Island and Thwaites glaciers do today.

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Abstract. Sub-ice shelf circulation and freezing/melting rates in ocean general circulation models depend critically on an accurate and consistent representation of cavity geometry. Existing global or pan-Antarctic topography data sets have turned out to contain various inconsistencies and inaccuracies. The goal of this work is to compile independent regional surveys and maps into a global data set. We use the S-2004 global 1-min bathymetry as the backbone and add an improved version of the BEDMAP topography (ALBMAP bedrock topography) for an area that roughly coincides with the Antarctic continental shelf. The position of the merging line is individually chosen in different sectors in order to capture the best of both data sets. High-resolution gridded data for ice shelf topography and cavity geometry of the Amery, Fimbul, FilchnerRonne, Larsen C and George VI Ice Shelves, and for Pine Island Glacier are carefully merged into the ambient ice and ocean topographies. Multibeam survey data for bathymetry in the former Larsen B cavity and the southeastern Bellingshausen Sea have been obtained from the data centers of Alfred Wegener Institute (AWI), British Antarctic Survey (BAS) and Lamont-Doherty Earth Observatory (LDEO), gridded, and blended into the existing bathymetry map. The resulting global 1-min Refined Topography data set (RTopo-1) contains selfconsistent maps for upper and lower ice surface heights, bedrock topography, and surface type (open ocean, grounded ice, floating ice, bare land surface).