Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE-SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10-100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings

Tectonic inheritance and continental rift architecture: Numerical and analogue models of the East African Rift System.

The western branch of the East African Rift is composed of an arcuate succession of elongate asymmetric basins, which differ in terms of interaction geometry, fault architecture and kinematics, and patterns of uplift/subsidence and erosion/sedimentation. The basins are located within Proterozoic mobile belts at the edge of the strong Tanzanian craton; surface geology suggests that the geometry of these weak zones is an important parameter in controlling rift development and architecture, although other processes have been proposed. In this study, we use lithosphere-scale numerical models and crustal-scale analogue experiments to shed light on the relations between preexisting structures and rift architecture. Results illustrate that on a regional scale, rift localization within the mobile belts at the curved craton's western border results in an arcuate rift system, which implies that under a constant extensional stress field, part of the western branch experienced orthogonal extension and part oblique extension. Largest depocenters are predicted to form mostly orthogonal to the extension direction, and smaller depocenters will form along the oblique parts of the rift. The varying extension direction along the rift zone furthermore results in lengthwise varying rift asymmetry, segmentation characteristics, and border fault architecture (trend, length, and kinematics). Analogue models predict that discrete upper crustal fabrics may influence the location of accommodation zones and control the architecture of extension-related faults at a local scale. Models support that fabric reactivation is responsible for the oblique-slip kinematics on faults and for the development of Z-shaped or arcuate normal faults typically documented in nature. Copyright 2007 by the American Geophysical Union

Constitutional Considerations of the Children\u27s Television Act of 1988: Why the President\u27s Veto Was Warranted

Late last year, President Reagan surprised many when he vetoed the Children\u27s Television Act of 1988, which would have limited the time available for commercials broadcast during children\u27s programming. His veto message referred to freedom of expression, but did not elaborate on first amendment concerns raised by the legislation. The author evaluates these and other issues and concludes that President Reagan\u27s veto was consistent with a sensitive approach to first amendment issues in the area of children\u27s advertising

Ontwikkelperspectieven en loopbanen van leraren: een advies van de Kritische Vrienden Lerarenagenda aan de minister en staatssecretaris

In november hebben de Kritische Vrienden van de Lerarenagenda een advies uitgebracht aan de bewindslieden van OCW over ontwikkelmogelijkheden en loopbaanpaden voor leraren. De kritische vrienden is een groep leraren, schoolleiders en lerarenopleiders die door de minister en staatssecretaris is ingesteld met als doel om de ontwikkeling en implementatie van de Lerarenagenda 2013-2020 kritisch te volgen. In het nieuwste advies gaan Marco Snoek en de andere leden van de Kritische Vrienden in op het belang van een samenhangende visie op ontwikkeling en loopbaanpaden van leraren, waarbij het perspectief van de leraar, ondersteuningsstructuren, loopbaanstructuren, competentiestructuren en lokale schoolculturen en –structuren in samenhang bekeken worden. Tevens schetsen de Kritische Vrienden drie modellen voor loopbaanpaden van leraren: Een model waarbij het individuele ondernemerschap van een leraar centraal staat Een model waarin sprake is van gestructureerde loopbaanpaden gekoppeld aan gerichte scholingstrajecten die daar op aansluiten (vergelijkbaar met het model in Singapore, zie het rapport van Louise Elffers hierover: Versterking van de loopbaanladder van leraren: wat kunnen we leren van Singapore? ) Een model waarbij teams centraal staan en waar binnen teams afspraken gemaakt worden wie voor welke periode een bepaalde rol op zich neemt. Dit laatste model heeft de voorkeur van de Kritische Vrienden omdat het minder statisch en meer flexibel is dan de bestaande loopbaanpaden via de functiemix. Het advies sluit nauw aan bij een rapport vanuit de Europese Commissie over de ontwikkeling van leraren: ‘Shaping career-long perspectives on teaching