Satellite Gravity and Geoid Studies Reveal the Formations Underlying Large-Scale Basin Structures
Carla Braitenberg2 and Jörg Ebbing1
1Geological Survey of Norway, Trondheim, Norway
2Earth Sciences, University of Trieste, Trieste, Italy
We compare results from studies of the global large-scale basins: Eastern Barents Sea basins in the high Arctic, the Michigan basin in North America, the Solimões, Amazon, Parnaìba and Paranà basins in South America, the Tarim basin in Central Asia and the Congo basin in Africa. These large-scale basins are often referred to as cratonic or intra-cratonic basins. Detailed study of satellite derived gravity anomalies, geoid undulations and the isostatic state of large-scale basin structures shows that these basins show a series of distinctive features: the basins show in general the presence of volcanic material, and a thick sedimentary succession, even with large variations in absolute thickness and aerial extension. Most striking is however that for the majority of the basins we find evidence for high-density material in the lower crust and/or upper mantle. These high-density structures compensate at least partly for the low-density sedimentary infill, while crustal thickness variations and Moho topography cannot be considered solely as mechanisms of compensation of the sedimentary loading. This is in clear contrast to rift type basins and formation of large-scale basins is apparently inked to large-scale lithospheric processes. The global comparison allows us also to test mechanism models, which might be valid for less well-known basins, as e.g. the Congo basin.
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