We present conceptual models for the tectono-sedimentary evolution of rift basins. Basin architecture depends upon a complex interaction between the three-dimensional evolution of basin linkage through fault propagation, the evolution of drainage and drainage catchments and the effects of changes in climate and sea/lake level. In particular, the processes of fault propagation, growth, linkage and death are major tectonic controls on basin architecture. Current theoretical and experimental models of fault linkage and the direction of fault growth can be tested using observational evidence from the earliest stages of rift development. Basin linkage by burial or breaching of crossover basement ridges is the dominant process whereby hydrologically closed rifts evolve into open ones. Nontectonic effects arising from climate, sea or lake level change are responsible for major changes in basin-scale sedimentation patterns. Major gaps in our understanding of rift basins remain because of current inadequacies in
sediment, fault and landscape dating.

Tectono-sedimentary evolution of active extensional basins

A simplified model of continental extension including lower crustal flow is developed. The model employs the thin sheet approximation in estimating lithospheric yield strength and gravitational buoyancy forces arising from lateral variations in crustal thickness and temperature. The effect of advection and diffusion of heat on the temperature structure and yield strength of the extending region is calculated. The viscosity of the lower crust, which controls its rate of flow, is estimated in a manner consistent with the yield strength calculation. The change in the force required to extend the lithosphere is calculated after a finite amount of extension. When this force increases, the zone of extension is assumed to widen; when it decreases, the extension remains localized. Material parameters affecting the model results are the density difference between the crust and mantle, the gradient of brittle yield stress with depth, the abundance of heat-producing elements within the crust, and the ductile strengths of the crust and mantle as a functions of temperature and strain rate. The model predicts three distinct modes of extension depending on the model crustal thickness, heat flow, and strain rate. The modes are (1) core complex mode (concentrated upper crustal extension with lower crustal thinning over a broad area and any mantle lithosphere extending in a local area), (2) wide rift mode (uniform crustal and mantle lithospheric thinning over a width greater than the lithospheric thickness), and (3) narrow rift mode (concentrated crustal and mantle lithospheric extension). Models with a dry olivine mantle rheology and a dry quartz or dry anorthosite crustal rheology are consistent with geologic observations of crustal thickness and heat flow for all three extensional modes. An analysis of the force changes due to extension, ignoring conduction of heat, is carried out to give greater insight into how variations in crust and mantle rheologic parameters affect model results. Crustal rheologies several orders of magnitude stronger or weaker than dry quartz give results inconsistent with observations. The model implies a temporal progression from core complex mode to wide rift mode to narrow rift mode. Data from the southern Basin and Range Province are consistent with this progression.

Modes of continental lithospheric extension

Neotectonics of Turkey – a synthesis

https://www.utdallas.edu/~rjstern/egypt/PDFs/Cenozoic%20Red%20Sea/BosworthRedSeaJAES05.pdf

The Red Sea and Gulf of Aden Basins

SUMMARY We use continuously recording GPS (CGPS) and survey-mode GPS (SGPS) observations to determine Euler vectors for relative motion of the African (Nubian), Arabian and Eurasian plates. We present a well-constrained Eurasia‐Nubia Euler vector derived from 23 IGS sites in Europe and four CGPS and three SGPS sites on the Nubian Plate (−0.95 ± 4.8 ◦ N, −21.8 ± 4.3 ◦ E, 0.06 ± 0.005 ◦ Myr −1 ). We see no significant (> 1m m yr −1 ) internal deformation of the Nubian Plate. The GPS Nubian‐Eurasian Euler vector differs significantly from NUVEL-1A (21.0 ± 4.2 ◦ N, −20.6 ± 0.6 ◦ E, 0.12 ± 0.015 ◦ Myr −1 ), implying more westward motion of Africa relative to Eurasia and slower convergence in the eastern Mediterranean. The Arabia‐ Eurasia and Arabia‐Nubia GPS Euler vectors are less well determined, based on only one CGPS and three SGPS sites on the Arabian Plate. The preliminary Arabia‐Eurasia and Arabia‐ Nubia Euler vectors are 27.4 ± 1.0 ◦ N, 18.4 ± 2.5 ◦ E, 0.40 ± 0.04 ◦ Myr −1 , and 30.5 ± 1.0 ◦ N, 25.7 ± 2.3 ◦ E, 0.37 ± 0.04 ◦ Myr −1 , respectively. The GPS Arabia‐Nubia Euler vector differs significantly from NUVEL-1A (24.1 ± 1.7 ◦ N, 24.0 ± 3.5 ◦ E, 0.40 ± 0.05 ◦ Myr −1 ), but is statistically consistent at the 95 per cent confidence level with the revised Euler vector reported by Chu & Gordon based on a re-evaluation of magnetic anomalies in the Red Sea (31.5 ± 1.2 ◦ N, 23.0 ± 2.7 ◦ E, 0.40 ± 0.05 ◦ Myr −1 ). The motion implied in the Gulf of Aqaba and on the Dead Sea fault (DSF) by the new GPS Nubia‐Arabia Euler vector (i.e. ignoring possible Sinai block motion and possible internal plate deformation) grades from pure left lateral strike-slip in the Gulf and on the southern DSF with increasing compression on the central and northern DSF with relative motion increasing from 5.6 to 7.5 mm yr −1 (± 1m m yr −1 ) from south to north. Along the northern DSF (i.e. north of the Lebanon restraining bend) motion is partitioned between 6 ± 1m m yr −1 left-lateral motion parallel to the fault trace and 4 ± 1m m yr −1 faultnormal compression. Relative motions on other plate boundaries (including the Anatolian and Aegean microplates) derived from the GPS Euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes (M > 6). Where data are available on fault-slip rates on plate bounding faults (North Anatolian fault, East Anatolian fault, Dead Sea fault, Red Sea rift), they are generally lower than, but not significantly different from, the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures.

/pdf/gps-constraints-on-africa-nubia-and-arabia-plate-motions-h9x6u7u4wg.pdf

François Berthelot

Papers

Subsidence in the gulf of suez: implications for rifting and plate kinematics