Thick Paleogene sequences occur in the southern deformed fold and thrust belt of the Himalayas. In this thesis I describe detailed litho- and biostratigraphy from ten key stratigraphic sections in the Kohat Basin, the Potwar Basin and the Trans Indus Ranges (TIR). These stratigraphies combined with microfacies analysis resulted in a new interpretation of the tectono-stratigraphic history of the area, which is dominated by India-Asia collision but where eustatatic effects can also be identified. Of particular interest is documenting the timing of the final closure of the northern rim of the Tethys caused by this collision. The Kohat and Potwar Basins represent foreland basins within the collision zone. Their stratigraphies document effects of local tectonics and eustatic sea level. The biostratigraphy is based on occurrences of larger benthic foraminifera. Taxonomy of the species is included in the thesis. The Paleogene rocks of the study area are divided into local larger benthic forminiferal biozones: BFZK 1- BFZK 6 in the Kohat Basin and BFZP 1-BFZP 3 in the Potwar Basin and the TIR. These local biozones are correlated to the global standard biozonation schemes of Höttinger (1960), Schaub (1981), and Serra Kiel et al. (1998). The ages of the sequences are Late Paleocene (Thanitian) to Middle Eocene (Upper Lutetian) in the Kohat Basin, and Late Paleocene (Thanitian) to Early Eocene (Middle Cuisian) in the Potwar Basin and the TIR. The sediments were deposited along a carbonate ramp platform in both areas (sensu Read, 1982, 1985). The sequence stratigraphic histories of the two basins are described as follows. In the Kohat Basin, Thanitian to Middle Cuisian strata record the first Transgressive-Regressive cycle (TRK 1). The first sequence boundary (SBK 1) is followed by Middle Cuisian-Upper Cuisian lowstand progradational deposition that marks the end of TRK 1 cycle. Middle Lutetian 1-Upper Lutetian strata represent the second Transgressive-Regressive cycle (TRK 2). The second sequence boundary (SBK 2) ends TRK 2 deposition, after which no more deposition took place. In the Potwar Basin and the TIR, Thanitian strata comprise the first Transgressive- Regressive cycle (TRP 1), whilst Lower Lllerdian-Middle Lllerdian 1 strata constitute the second Transgressive-Regressive cycle (TRP 2). Middle Lllerdian 2 to Middle Cuisian strata mark the third Transgressive-Regressive cycle (TRP 3). Three sequence boundaries (the SBP 1, the SBP 2 and the SBP 3), marked by exposure surfaces, separate the three depositional cycles. The SBP 1 and SBP 2 sequence boundaries are controlled by local tectonics. In contrast the SBP 3 and SBK 1 sequence boundaries are synchronous at 49.5 Ma, and represent a phase of significant relative sea level fall, possibly driven by the combined effect of uplift (collision tectonics) and eustatic sea level fall (e.g. Haq et al., 1987). This implies that proto-closure of the northern rim of the Tethys occurred around 49.5 Ma. Reestablishment of marine conditions in the Kohat Basin occurred in the Middle Lutetian 1 around 45.8 Ma, possibly caused by a combination of flexural loading of the Indian plate (Pivinik & Wells, 1996) and eustatic sea-level rise (e.g. Haq et al., 1987). The final closure of the Tethys, marked by the end of marine sedimentation in the Kohat Basin, occurred in the Upper Lutetian (41.2 Ma). Finally, Himalayan foreland molasses sedimentation occurred during Miocene to Pliocene.

This study uses a new integrated outcrop data and airborne lidar from Slaughter Canyon, New Mexico, to quantitatively characterize the cycle-scale facies architecture within the G23-G26 high frequency sequences of the Yates Formation. High frequency cycle-scale mapping of these sequences shows sedimentological evidence for accommodation reduction associated with the Permain composite sequence (CS) 13 highstand (G23-G25). Development of the G26 HFS additionally demonstrates the isochronous balance of mixed carbonate-siliciclastic deposition across the Yates-Capitan reef-rimmed shelf during the initial CS-scale transgression following significant exposure and bypass of sand across the shelf. This sequence framework is quantitatively analyzed using progradation to aggradation (P/A) ratios, facies proportions, facies tract dip width, and facies tract bedding angles to evaluate the interplay of eustacy and syndepositional deformation as drivers of stratigraphic architecture. The sequences defined here developed in response to both eustacy and syndepositional deformation, but individual facies distributions and cycle stacking patterns were largely controlled by eustacy; while facies, cycle, and sequence thicknesses as well as facies bedding angles were locally influenced by syndepositional faulting. A reconstruction of each high frequency sequence and stepwise documentation of post-depositional fault displacement and HFS basinward rotation was generated using the lidar data. This analysis shows that the G23-G26 HFS developed basinward-dipping depositional topography from the shelf crest to the shelf margin reef. This geometry was largely unaltered by syndepositional faults during individual HFS deposition, but was rotated basinward shortly thereafter by younger fault movement. The accommodation trends recorded in this largely shelf crest to shelf margin window can be additionally projected into the middle shelf producing zones of the prolific Yates-aged reservoirs on the Northwest Shelf and Central Basin Platform. / text

In South Central Cut Bank Sand Unit (SCCBSU) of Cut Bank field, primary production and waterflood projects have resulted in recovery of only 29 % of the original oil in place from heterogeneous, fluvial sandstone deposits. Using highresolution sequence stratigraphy and geostatistical analysis, I developed a geologic model that may improve the ultimate recovery of oil from this field. In this study, I assessed sequence stratigraphic concepts for continental settings and extended the techniques to analyze low-accommodation alluvial systems of the Cut Bank and Sunburst members of the lower Kootenai formation (Cretaceous) in Cut Bank field. Identification and delineation of five sequences and their bounding surfaces led to a better understanding of the reservoir distribution and variability. Recognition of stacking patterns allowed for the prediction of reservoir rock quality. Within each systems tract, the best quality reservoir rocks are strongly concentrated in the lowstand systems tract. Erosional events associated with falling baselevel resulted in stacked, communicated (multistory) reservoirs. The lowermost Cut Bank sandstone has the highest reservoir quality and is a braided stream parasequence. Average net-to-gross ratio value (0.6) is greater than in other reservoir intervals. Little additional stratigraphically untapped oil is expected in the lowermost Cut Bank sandstone. Over most of the SCCBSU, the Sunburst and the upper Cut Bank strata are valley-fill complexes with interfluves that may laterally compartmentalize reservoir sands. Basal Sunburst sand (Sunburst 1, average net-to-gross ratio ~0.3) has better reservoir quality than other Sunburst or upper Cut Bank sands, but its reservoir quality is significantly less than that of lower Cut Bank sand. Geostatistical analysis provided equiprobable representations of the heterogeneity of reservoirs. Simulated reservoir geometries resulted in an improved description of reservoir distribution and connectivity, as well as occurrences of flow barriers. The models resulting from this study can be used to improve reservoir management and well placement and to predict reservoir performance in Cut Bank field. The technical approaches and tools from this study can be used to improve descriptions of other oil and gas reservoirs in similar depositional systems.

L’évolution des systèmes sédimentaires jurassiques (Pliensbachien-Bajocien) dans le secteur de Zaouiat-Ahançal (Haut Atlas, Maroc) est localement influencée par des mouvements diapiriques associés à la ride du Jbel Azourki. Cette structure tectonique complexe suit un tracé en baïonnette d’orientation globale OSO-ENE sur près de 60 kilomètres, ponctué par six affleurements de matériel diapirique triasique. L’objectif de cette thèse est de caractériser l’impact du diapirisme sur la géométrie des dépôts et sur la distribution des faciès au sein de trois systèmes de dépôt successifs : (1) un système carbonaté de plate-forme peu profonde (Formations d’Aganane, de Jbel Choucht et d’Assemsouk) (2) des systèmes de rampe mixte silicoclastique et carbonatée (Formations de Tamadout, d’Amezraï, de Tafraout et d’Aguerd-n-Tazoult), (3) et un système carbonaté oolitique (Formation de Bin-El-Ouidane). Une cartographie détaillée des unités stratigraphiques et des unités de faciès, ainsi qu’une série de quatorze coupes géologiques de la ride diapirique du Jbel Azourki ont ainsi été réalisées. L’étude des interactions entre sédimentation et diapirisme révèle un enregistrement continu de la déformation diapirique sur l’ensemble de la série sédimentaire, et a permis d’établir une chronologie de l’activité diapirique dans le secteur de Zaouiat-Ahançal. L’unité des calcaires inférieurs (1) enregistre une déformation polyphasée marquée par le développement localisé, au sein de la plate-forme, de bassins d’extension kilométrique caractérisés par une sédimentation hémipélagique et gravitaire (rim basins). Ces bassins circonscrits aux diapirs sont limités par des bordures de plate-forme bioconstruites à Lithiotis, de type aggradant ou érosif. À partir du Pliensbachien terminal, les déformations syndiapiriques se manifestent dans les unités mixtes (2), d’une part à l’échelle plurikilométrique avec l’accumulation de plusieurs milliers de mètres de dépôts, contrôlée par la variation latérale du taux de subsidence entre et au sein des compartiments nord et sud de la ride, et d’autre part à l’échelle hectométrique de la bordure du diapir avec des géométries caractéristiques et des variations de faciès (micro plates-formes à oolites et coraux). La ride diapirique perce en surface pendant le dépôt des unités mixtes, puis est recouverte par l’unité transgressive peu déformée des calcaires supérieurs (3) à l’Aalénien terminal. Les paramètres de contrôle de la géométrie des dépôts et de la distribution des faciès autour de la ride diapirique du Jbel Azourki correspondent aux variations locales de subsidence liées aux mouvements de la couche de sel en profondeur, au taux de sédimentation et à leur rapport relatif. Ils s’inscrivent dans un contexte tectonique régional, et climatique global, qui définit l’accommodation générale et le type de remplissage sédimentaire du bassin atlasique. Le type de sédimentation, carbonatée ou mixte, joue un rôle prépondérant dans ces manifestations tectono-sédimentaires. / The evolution of the Jurassic sedimentary systems (Pliensbachian-Bajocian) in Zaouiat-Ahançal area (High Atlas, Morocco) is locally controlled by diapiric movements related to the Jbel Azourki ridge. This nearly-60-kilometer-long complex tectonic structure follows an overall WSW-ENE “bayonet-shape” outline, punctuated by six Triassic diapiric outcrops. The aim of this thesis is to characterize the role of diapirism on depositional geometries and facies distribution in three successive sedimentary systems: (1) a shallow-carbonate platform system, (2) mixed siliciclastic- and carbonate-ramp systems and (3) an oolitic-carbonate system. Therefore, a detailed geological map with the stratigraphic and facies units has been realized, as well as a set of fourteen geological sections across the Jbel Azourki diapiric ridge. The analysis of the interactions between sedimentation and diapirism has revealed a continuous recording of diapiric deformation by the entire sedimentary succession, allowing the establishment of a chronology of diapiric activity in the Zaouiat-Ahançal area. The lower-carbonate unit (1) records a polyphase deformation with the development of localized kilometer-scale basins within the platform, characterized by hemipelagic and gravity-flow deposits (rim basins). These basins are confined around the diapirs and bounded by Lithiotis-bioconstructed platform margins, which can be aggradational or erosional. From the late Pliensbachian, the mixed units (2) were affected firstly by syn-diapiric deformations at a pluri-kilometer scale, with the accumulation of several thousand-meter-thick deposits, controlled by lateral variations of the subsidence rate in and between the northern and southern flanks of the ridge, and secondly by syn-diapiric deformations at a hectometer- “diapir-edge” scale, with characteristic geometries and facies variations (oolite- and coral-rich micro platforms). The diapiric ridge reached the surface during the deposition of the mixed units and was finally capped by slightly deformed transgressive upper-carbonate unit (3) in the late Aalenian. The controlling factors on depositional geometries and facies distribution around the Jbel Azourki diapiric ridge are the local variations of the subsidence rate related to salt-movement, the sedimentation rate, and their relative ratio. They are part of the regional tectonic and global climate settings which defined the overall accommodation rate and the sedimentary filling of the atlasic basin. The type of sedimentation, carbonate- or mixed-dominated, played a major role in these tectonic-sedimentary responses.