The objective of this project is about a kinematic analysis of a shear zone, specifically a graben structure. The surface of the study area has also been investigated, this is to understand if a faulting reactivation has occurred due to glacial impact. The graben structure is exposed along a road cut, next to the E18 highway at Ekolsund, 14km east of Enköping. The results of the report are based on field studies of the geometrical relationship pattern of fracture planes, relative displacement along fracture and a kinematic analysis of movements along fractures. A high resolution terrain model was acquired in the analyzing of the graben structure formation and to create a geometrical 3D brittle deformation model. This model was applied to reconstruct the deformation process. The area contains a more than 1,1km long dextral NE-trending strike-slip fault feature in a polydeformed Precambrian bedrock. The fault is connected NE to one of the regional structure that delimits the bedrock blocks. The fault is visible both as a topographical feature from the ground and from aerial photos. While the project followed through it was clear that the area had been subjected to reactivation. The evidence for this claim stems from an observed semivertical fracture plane with conjugating subhorizontal striations markers that contain an alternating plunge and trend. Other evidence for a reactivation scenario is the fault gouges that contain horizontal striation as well as steep plunging striation, indicating a dip-slip faulting movement. The main zone of faulting displays lower altitude than the surrounding rock. This indicates an asymmetric graben structure that has been subjected to polydeformation. When analyzing the results, it is concluded that a pull-apart basin event has occurred. It’s highly possibly that it has been undergoing modifications during its geological history, resulting in a polydeformed reactivation of the minor faults outlining the graben structure. / Syftet med denna studie är att utföra en kinematisk analys av en förkastningszon, speciellt där en mindre graben struktur utbildats. Ytan för det studerade området är även det viktigt, det är för att förstå ifall en förkastningsreaktivering har skett i och med en glacial påverkan. Graben strukturen är blottad längs en vägskärning, utmed E18 vid Ekolsund, 14km österut om Enköping. Resultatet av rapporten är baserat på fältstudier med fokus på geometriska relationsmönster hos sprickplan, relativa förskjutningar längs sprickor och en kinematisk analys av rörelser längs sprickor. En högupplöst terrängmodell var erhållen vid analys av grabenstrukturens formation och för att skapa en 3D sprödtektonisk deformationsmodell. Modellen var tillämpad vid rekonstruering av deformationsprocessen. Området innefattar en mer än 1,1km lång dextral NO-orienterad strike-slip förkastning i en polydeformerad Prekambrisk berggrund. Förkastningen är ansluten NO till en av de regionala strukturerna som begränsar berggrundsblocken. Förkastningen är synlig både på marknivå och från flygfoton. Medan projektet fortlöpte blev det tydligare att området blivit utsatt för en reaktivering. Beläggen för detta påstående grundar sig i de observerade semi-vertikala sprickplanen med konjugerande subhorisontala striationer som har alternerande stupning och trend. Andra belägg för ett reaktiveringsscenario är de fault gouge strukturerna som innehåller horisontala striationer såväl som stupande striationer, vilket indikerar på en dip-slip förkastningsrörelse. Huvudzonen av förkastningen uppvisar lägre altitud än kringliggande bergyta. Det här indikerar en asymmetrisk graben struktur som har utsatts för polydeformation. Vid analys av resultatet, så kan det sammanfattas att en pull-apart basin förkastning har inträffat. Däremot är det mycket möjligt att zonen har undergått fler modifikationer under dess geologiska historia, vilket har resulterat i en polydeformerad reaktivering av mindre förkastningar som gett kontur dragen åt graben strukturen.

This study presents numerical modeling of geologic processes based on Discrete Element Method (DEM), including modeling of pull-apart basin development based on Particle Flow Code (PFC) and simulation of deformation and earthquake potential of Ordos Block (China) under present tectonic stress regime based on Universal Distinct Element Code (UDEC). A scale-independent modeling approach based on PFC2D has been established to simulate the development of pull-apart basins. The micro-scale PFC models are used to investigate crack propagation and basin development in releasing sidestep systems with pure strike-slip, transtensional, and transpressional master faults, respectively. In each system, three typical models including 30° underlapping, 90° non-overlapping, and 150° overlapping releasing sidesteps are chosen. The modeling results are compared with pull-apart basins in nature. The geometric differences of pull-apart basins result from both the initial strike-slip fault geometries and its various evolution stages. Rhomboidal basins which have larger basin length than the amount of motion form in overlapping systems and do not progress through the spindle-shaped and lazy-Z-shaped stages such as the Dead Sea basin. Rhomboidal basins with cross-basin faults tend to form in underlapping systems. Finally, the origin of rhomboidal pull-apart basins, depocenters of pull-apart basins, cross-basin faults and their significances, models for pull-apart basin development, and minimum displacements and ages to form pull-apart basins are discussed. A two-dimensional UDEC model involving Ordos Block and adjacent areas is set up. Boundary conditions based on present tectonic regime are assumed. Block rotations, shear stress and displacement on faults, ratio of shear to normal force are simulated. Slip tendency which represents the assessment of the potential for causing slip on individual faults and earthquake-prone of the faults is predicted. Modeling results are compared with geologic evidences.

>Magister Scientiae - MSc / The thesis provides a study into the main structural features of the Namaqua Region and their relation to the intrusion of the Keimoes Suite. This was achieved by producing a digitized map of the Namaqua Region structural framework using a LandSAT image and MOVE software for remote sensing. The structural framework showed an array of shear zones and fault systems which trend in a NW-SE direction. The validation of the sense of movement, location and orientation of the shear zones was done by field mapping. The general orientation of all shear zones was NW-SE. The sense of movement along the Neusspruit, Boven Rugzeer and Trooilapspan shear zones was found to be dextral strike slip movement and the Cnydas shear zone had a sinistral strike slip movement. The location of the shear zones were determined by analyzing the deviation in general foliation trend which was visualized using Rose Diagrams. The field data and the remote sensing were found to agree with the transpressive environment of the Namaqua Region. The oblique collision of the Namaqua-Natal crustal block with the Kaapvaal Craton during the orogenic event at ~1.2 Ga created a compressionalgeotectonic setting which allowed for the intrusion of the early to late syn-tectonic Keimoes Suite granites. The lateral escape of the Namaqua-Natal crustal block took place along the western margin of the Kaapvaal Craton. This was brought on by prolonged compression which resulted in the formation of a releasing bend in the Namaqua Region. This releasing bend produced the negative flower structure with dextral shear zones which facilitated the intrusion of the post-tectonic Keimoes Suite granites.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study investigates the crustal structure, and assesses the qualitative and quantitative impacts of crust-mantle dynamics on subsidence pattern, past and present-day thermal field and petroleum system evolution at the southern South African continental margin through the application of a multi-disciplinary and multi-scale geo-modelling procedure involving both conceptual and numerical approaches. The modelling procedure becomes particularly important as this margin documents a complex interaction of extension and strike-slip tectonics during its Mesozoic continental rifting processes. Located on the southern shelf of South Africa, the Western Bredasdorp Basin (WBB) constitutes the focus of this study and represents the western section of the larger Bredasdorp sub-basin, which is the westernmost of the southern offshore sub-basins. To understand the margin with respect to its present-day structure, isostatic state and thermal field, a combined approach of isostatic, 3D gravity and 3D thermal modelling was performed by integrating potential field, seismic and well data. Complimenting the resulting configuration and thermal field of the latter by measured present-day temperature, vitrinite reflectance and source potential data, basin-scale burial and thermal history and timing of source rock maturation, petroleum generation, expulsion, migration and accumulation were forwardly simulated using a 3D basin modelling technique. This hierarchical modelling workflow enables geologic assumptions and their associated uncertainties to be well constrained and better quantified, particularly in three dimensions. At present-day, the deep crust of the WBB is characterised by a tripartite density structure (i.e. prerift metasediments underlain by upper and lower crustal domains) depicting a strong thinning that is restricted to a narrow E-W striking zone. The configuration of the radiogenic crystalline crust as well as the conductivity contrasts between the deep crust and the shallow sedimentary cover significantly control the present-day thermal field of the study area. In all respects, this present-day configuration reflects typical characteristics of basin evolution in a strike-slip setting. For instance, the orientations of the deep crust and fault-controlled basin-fill are spatially inconsistent, thereby indicating different extension kinematics typical of transtensional pull-apart mechanisms. As such, syn-rift subsidence is quite rapid and short-lived, and isostatic equilibrium is not achieved, particularly at the Moho level. Accompanied syn-rift rapid subsidence and a heat flow peak led to petroleum preservation in the basin since the Early Cretaceous. Two additional post-rift thermal anomalies related to the Late Cretaceous hotspot mechanism and Miocene margin uplift in Southern Africa succeeded the syn-rift control on maturation. This thermal maturity of the five mature source rocks culminated in four main generation and three main accumulation phases which characterise the total petroleum systems of the WBB. The Campanian, Eocene and Miocene uplift scenarios episodically halted source maturation and caused tertiary migration of previously trapped petroleum. Petroleum loss related to the spill point of each trap configuration additionally occurs during the Late Cretaceous-Paleocene and Oligocene-Early Miocene. The timing and extent of migration dynamics are most sensitive to the geological scenario that combined faulting, intrusive seal bypass system and facies heterogeneity. In fact, for models that do not incorporate facies heterogeneity, predicted past and present-day seafloor leakage of petroleum is largely underestimated. This complex interplay of generation and migration mechanisms has significant implications for charging of petroleum accumulations by multiple source rocks. Due to early maturation and late stage tertiary migration, the syn-rift source rocks particularly Mid Hauterivian and Late Hauterivian source intervals significantly control the extent of petroleum accumulation and loss in the basin. Lastly, the modelled 3D crustal configuration and Mezosoic to Cenozoic thermal regime of the WBB dispute classic uniform lithospheric stretching for the southern South African continental margin. Rather, this PhD thesis confirms that differential thinning of the lithosphere related to a transtensional pull-apart mechanism is the most appropriate for accurately predicting the evolution of basin and petroleum systems of the margin. Also, the presented 3D models currently represent the most advanced insights, and thus have clear implications for assessing associated risks in basin and prospect evaluation of the margin as well as other similar continental margins around the world. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die korsstruktuur en evalueer die kwalitatiewe en kwantitatiewe impakte van kors-mantel-dinamika op insinkingspatroon, die termiese veld en petroleumstels evolusie aan die suidelike Suid-Afrikaanse kontinentale grens, in die hede en die verlede, deur die toepassing van ’n multidissiplinêre en multiskaal-geomodelleringsprosedure wat beide konseptuele en numeriese benaderings behels. Die modelleringsprosedure veral is belangrik aangesien hierdie kontinentale grens ’n komplekse interaksie van uitbreidings- en strekkingsparallelle tektoniek gedurende die Mesosoïese vastelandskeurprosesse daarvan dokumenteer. Omdat dit op die suidelike platvorm van Suid-Afrika geleë is, maak die Westelike Bredasdorp Kom (WBK) die fokus van hierdie studie uit, en verteenwoordig dit die westelike deel van die groter Bredasdrop-subkom, wat die verste wes is van die suidelike aflandige subkomme. Om die grens met betrekking tot sy huidige struktuur, isostatiese staat en termiese veld te verstaan, is ’n kombinasie benadering bestaande uit isostatiese, 3D-gravitasie- en 3D- termiese modellering gebruik deur potensiëleveld-, seismiese en boorgatdata te integreer Ondersteunend totot die gevolglike konfigurasie en termiese veld van die laasgenoemde deur middel van hedendaagse temperatuur, soos gemeet, vitriniet-refleksiekoëffisiënt en bronpotensiaal data, komskaal-begrawing en termiese geskiedenis en tydsberekening van brongesteentematurasie, is petroleumgenerasie, -uitwerping, -migrasie en -akkumulasie in die toekoms gesimuleer deur gebruik te maak van ’n 3D-kommodelleringstegniek. Hierdie hierargiese modelleringswerkvloei maak dit moontlik om geologiese aannames en hulle geassosieerde onsekerhede goed aan bande te lê en beter te kwantifiseer, veral in drie dimensies. In die hede word die diep kors van die WBK gekarakteriseer deur ’n drieledige digtheidstruktuur (met ander woorde voorrift-metasedimente onderlê deur bo- en benedekors domeine) wat dui op ’n baie wesenlike verdunning, beperk tot ’n dun O-W-strekkingsone. Die konfigurasie van die radiogeniese kristallyne kors, sowel as die konduktiwiteitskontraste tussen die diep kors en die vlak sedimentêre dekking, beheer grotendeels die hedendaagse termiese veld van die studiearea. Hierdie hedendaagse konfigurasie weerspieël in alle opsigte tipiese eienskappe van kom-evolusie in ’n skuifskeur omgewing. Byvoorbeeld, Die oriëntasies van die diep kors en verskuiwingbeheerde komsedimentasie byvoorbeeld is ruimtelik inkonsekwent en dui daardeur op verskillende ekstensiekinematika, tipies van transtensionale tensiemeganisme. As sulks, is sin-rift-versakking taamlik vinnig en kortstondig, en word isostatiese ekwilibrium nie by die Moho-vlak, in die besonder, bereik nie. Samehangende sin-rift vinnige versakking en hittevloeihoogtepunt het gelei tot petroleum behoud in die kom sedert die vroeë Kryt. Twee bykomende post-rift termiese anomalieë wat verband hou met die laat Kryt-“hotspot” meganisme en die Mioseense kontinentale grensopheffing in Suidelike Afrika het die sin-rift-beheer met maturasie opgevolg. Hierdie termiese maturiteit van die vyf gematureerde brongesteentes het in vier hoofgenerasie- en drie hoofakkumulasie fases, wat die totaliteit van die petroleumstelsels van die WBK karakteriseer, gekulmineer. Die Campaniese, Eoseense en Mioseense opheffings senarios het episodies bronmaturasie gestop en tersiêre migrasie van petroleum wat vroeër opgevang was veroorsaak. Addisioneel vind petroleumverlies gekoppel aan die spilpunt van elke opvanggebiedkonfigurasie tydens die laat Kryt-Paleoseen en Oligoseenvroeë Mioseen plaas. Die tydstelling en omvang van migrasiedinamika is die sensitiefste vir die geologiese scenario wat verskuiwing, seëlomseilingstelsel en fasiesheterogeniteit kombineer. Trouens, vir modelle wat nie fasiesheterogeniteit inkorporeer nie, is voorspellings van vroeëre en huidige seebodemlekkasie van petroleum grotendeels onderskattings. Hierdie komplekse wisselwerking van generasie- en migrasiemeganismes het beduidende implikasies vir die laai van petroleumakkumulasies deur veelvoudige brongesteentes. Vanweë vroeë maturasie en laatstadiumtersiêre migrasie, oefen die sin-rift-brongesteentes, veral middel Hauterivium- en laat Hauteriviumbronintervalle, beduidende beheer oor die omvang van petroleumakkumulasie en -verlies in die kom uit. Laastens weerspreek die gemodelleerde 3D-korskonfigurasie en Mesosoïese-tot-Senosoïesetermiese regime van die WBK ’n klassieke uniforme litosferiese rekking vir die suidelike Suid- Afrikaanse kontinentale grens. Inteendeel, hierdie PhD-proefskrif bevestig dat ’n differensiële verdunning van die litosfeer, gekoppel aan ’n transtensiemeganisme, die beste geskik is om ’n akkurate voorspelling oor die evolusie van kom- en petroleumstelsels van die kontinentale grens mee te maak. Verder, verteenwoordig die 3D-modelle, wat hier aangebied word, tans die mees gevorderde insigte, en het hierdie modelle dus duidelike implikasies vir die assessering van verwante risiko’s in kom- en petroleum teikene valuering van die kontinentale grens, so wel as van ander soortgelyke kontinentale grense regoor die wêreld.

La période à 2.1 Ga du Craton d'Afrique de l'Ouest est une période de production massive de leucogranites. Le batholite de Ferkessédougou (Côte d'Ivoire) est, tant du point de vue de sa localisation, de son extension, que de son histoire dans la littérature géologique, un élément majeur de l'interprétation de la géodynamique du Paléoprotérozoïque. Tour à tour considéré comme un granite de ride augéosynclinale puis un granite typique de collision de type moderne, il n'en demeure pas moins le jalon d'un accident crustal NNE-SSW important du Paléoprotérozoïque : le linéament GFB (Greenville-Ferkessédougou-Bobodioulasso). Son étude et son interprétation s'inscrivent dans le débat sur la validité de la tectonique des plaques à cette période. Par analyse satellitale, nous montrons que ce batholite de 400 km de long sur une cinquantaine de large est en fait constitué d'une grande quantité de plutons adjacents relativement proches pétrographiquement. Le contexte général de son encaissant métavolcanique et/ou métasédimentaire birimien (2.2 Ga à 2.1 Ga) faiblement déformé et épizonal ainsi que l'absence de déformations tangentielles additionnelles traduisent la faiblesse de l'épaississement crustal synchrone de sa genèse. Sa fabrique déterminée par analyse structurale classique et par analyse de susceptibilité magnétique est double. La première "magmatique" est le plus souvent coaxiale, d'orientation et de pendages variables. Elle dessine des trajectoires courbes et traduit la mise en place des plutons. Elle est l'équivalent de ce qui a été rapporté à la déformation D1 autour de granites anciens. La seconde, magmatique à post-solidus, beaucoup mieux réglée, souvent constrictive ou non-coaxiale, est l'image d'un champ de contrainte régional transcurrent qui se rapporte à la déformation D2 classique dans la chronologie du craton birimien. Les plutons du batholite granitique de Ferké sont syntectoniques de cette grande phase de raccourcissement (2.1 Ga à 2.07 Ga) du birimien. Le passage en revue des différents modèles de plutons, l'analyse du secteur SW de la Côte d'Ivoire présentant des dykes granites à deux micas et des faciès métamorphiques de plus haut grade, un survol des formations de l'Imataca au Surinam, ainsi que le bilan de l'analyse structurale, nous amènent à proposer un modèle 3D pour le batholite de Ferké. Il correspondrait à un ensemble de petits plutons de forme laccolithique engagés dans la croûte superficielle entre les métasédiments épizonaux birimiens dits "de bassin", des gneiss et micaschistes probablement d'âge compris entre 2.2 et 2.1 Ga. Ces plutons seraient alimentés par un faisceau de dykes issus de la fracturation par ouverture en pull-apart du bassin sédimentaire SASCA-Bandama-Bobodioulasso. La fusion de la croûte essentiellement de type ceinture verte/TTG (absence de traces de matériel archéen), à la verticale du bassin subsident, aura incorporé du matériel sédimentaire de bassin. L'apport de chaleur nécessaire à la compensation de la faiblesse de l'épaississement aurait été fourni par le jeu décrochant des fractures majeures des pull-aparts. La place nécessaire à la mise en place des plutons exige une montée de ces derniers à la fin de la période extensive à la faveur de multiples cauldron-subsidences. Les conditions et régimes des deux déformations principales impliquent un lapse de temps très court entre la stabilisation de l'ouverture des bassins et leur fermeture. Par ailleurs, la variation du niveau structural du Nord-Est vers le Sud-Ouest, en particulier vers la zone probable de l'équivalent-racine au Vénézuéla-Surinam, montre un approfondissement et le rapprochement d'une croûte archéenne vers le SW alors qu'elle n'était jusqu'à présent reconnue que vers l'Ouest (Guinée, Dorsale de Man) ou soupçonnée vers l'Est au Ghana.