Parameterized Rift Development and Upper Mantle Anomalies

Abstract

Seidler, E. and Jacoby, W.R. 1981. Parameterized rift development and upper mantle anomalies. In: J.H. Illies (Editor), Mechanism of Graben Formation. Tectonophysics, 73: 53–68. The evolution of rift zones is studied by comparing some of their parameters; parameters are e.g. the “regional” and “axial” values and the “amplitudes” of topography, Bouguer, and free air gravity anomalies. The study includes the Rhine Graben, Baikal, East Africa, Afar, the Red Sea, Hon Graben, Godawari Rift, and others. We attempt to recognize trends e.g. with age. The most interesting results are: (1) the grouping into two families of rift zones which we call “continental” and “oceanic”; (2) the decay of the negative “axial” Bouguer anomaly with age toward zero while the “oceanic” trend overshoots zero; (3) the rise and fall of the “regional” altitude of the rift shoulders with age or time. Although the approach is crude and involves some problems, the results are encouraging. They can be explained plausibly with an isostatic model of a hot low-density front rising through the lower lithosphere and causing uplift, doming, and rifting of the crust and giving the characteristic gravity anomalies at the same time.