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Abstract: This palynostratigraphic study of Mesozoic successions in hydrocarbon-prospective Tanzanian coastal basins utilizes cores, ditch cuttings, and outcrop samples. These contain rich and diverse dinoflagellate suites ranging in age from Middle Jurassic (Bajocian) to earliest late Cretaceous (Cenomanian). Spores and pollen grains are also recorded, but these are, with some exceptions, subordinate to the dinoflagellate components.In the systematic section, one new dinoflagellate cyst genus, Kipatimudinium, is formally described and nine new species are established: Amphorulla ruvuense, Dichadogonyaulax mandawaense, Egmontodinium annaiae, Hystrichodinium playfordii, Kipatimudinium foliatum (type species), Limbodinium patulum, Pseudoceratium redactum, Sentusidinium tanzaniensis, and Yalkalpodinium africanum. Six, informal, stratigraphically successive dinoflagellate assemblages are distinguished:Assemblage I (Bajocian-Bathonian); Assemblage II (Callovian); Assemblage III (Oxfordian); Assemblage IV (Kimmeridgian-Tithonian); Assemblage V (Berriasian-Barremian); and Assemblage VI (Aptian-Cenomanian).Coastal Tanzania appears referable to the Austral dinoflagellate realm due to the presence of, inter alia, Broomea ramosa, Komewuia glabra, Wanaea clathrata, and Wanaea digitata. Some minor biostratigraphic anomalies are noted, including the introduction of Glossodinium dimorphum; this is datable as early Oxfordian in Tanzania whereas in Australasia the species appears earlier (in the Callovian). A few noteworthy quantitative phenomena are evident; for instance, the abundance of Lithodinia jurassica in the vicinity of the Callovian-Oxfordian boundary and the marked increase of Wanaea spp. in the Oxfordian, specifically in the Ruvu Basin of the northern coastal belt. These events are of chronostratigraphic significance and could be applicable to regional correlation. Middle-Late Jurassic assemblages show a conspicuous degree of cosmopolitanism, and include some species previously considered to be restricted to certain regions in the low and high latitudes.The Early Cretaceous (Berriasian-Barremian) assemblages show close affinity to the Tethyan Realm. The latest Early Cretaceous (Albian) to earliest Late Cretaceous (Cenomanian) strata are allied to the Albian-Cenomanian Elaterates province. The presence of elater-bearing pollen in offshore and onshore sections of Tanzania indicates that the elaterates had a wider geographic distribution than previously reported: i.e., extending beyond the northern part of the African and South American continents.The lower part of the Kipatimu Formation, which contains Assemblage IV, yielded Komewuia glabra, Broomea ramosa, and Rigaudella aemula and their presence precludes the Early Cretaceous age previously ascribed to this part of the formation. Likewise the Makonde and Mkindani Beds have yielded typically Early Cretaceous pollen grains including Classopollis braziliensis, Retitricolpites vulgaris, and Elaterocolpites castelainii.The Jurassic/Cretaceous boundary is coincident with the upper limit of Assemblage IV based on the last appearances of, in particular, Komewuia glabra and Rigaudella aemula. Within the Kipatimu Formation (as represented in wells SS-5 and SS-7), the systemic boundary appears conformable. But elsewhere in the coastal belt, the boundary is clearly unconformable.On the basis of palynostratigraphic data, significant biostratigraphic events, such as introductions and exits of certain dinoflagellate species often match sequence boundaries.From palynofacies analyses and palynostratigraphic data the Kipatimu Formation is dominated by phytoclasts indicating high terrestrial inputs during its deposition. Abundance of black wood (of high buoyancy) in the majority of samples implies high energy settings and abundance of brown wood (less buoyant) is an indication of a sudden terrestrial input into the marine system. The organic composition of sedimentary rocks is an important means of which the depositional history of the enclosing sediments can be understood. Different environmental settings clearly influence the character of palynofacies. For example, abundant chorate cysts (e.g., Systematophora spp.) in samples from the upper sections of SS-5 suggest open marine settings. Therefore, palynofacies analyses can be viewed as providing useful pointers to interpreting the environmental circumstances in which the rocks, in this case the Kipatimu Formation, were deposited.

The Twin Creek Limestone of Middle Jurassic age was studied in the Tunp, Salt River, and Wyoming Ranges in southwestern Wyoming. Modern carbonate environments and their ancient analogs were compared with information obtained from field study and petrographic analysis of samples of the Twin Creek Limestone in order to delineate environments of deposition, paleogeography, and diagenetic history. Six major lithofacies were recognized: (1) carbonate mudstone; (2) carbonate mudstone breccia; (3) fossiliferous wackestone; (4) packstone-grainstone; (5) terrigenous mudstone; and (6) sandstone. These lithofacies were deposited in a variety of environments, including outer shelf platforms (carbonate mudstone and fossiliferous wackestone), oolitic sand belts (packstone-grainstone), open to restricted lagoons (carbonate mudstone, fossiliferous wackestone, and terrigenous mudstone), tidal flats, and supratidal environments (terrigenous mudstone, sandstone and carbonate mudstone breccia). The Twin Creek epeiric seaway experienced two major transgressions (early Bajocian and late Bathonian-early Cal lovian) and two regressions (early Bathonian and middle Callovian). Lateral migration of the adjacent facies occurred in response to these changes in sea level. Eogenetic features include minor compaction, micritization, coarse fibrous rim cementation, granular cementation, syntaxial rim cementation and silicification of carbonates. These features were produced in environments ranging from freshwater phreatic to marine phreatic. Mesogenetic diagnesis was characterized by pressure-solution features and neomorphism. Telogenetic features are limited to calcite vein-fillings and oxidation coatings on carbonate and detrital gains and cements.

<p>The Middle Jurassic Tecocoyunca Group of northeastern Guerrero, Mexico is situated on the allochthonous Mixteca tectostratiqraphic terrane. This group represents an overall transgressive trend with a few minor fluctuations of base level. Foreshore, shoreface, barrier island, washover, and laqoonal facies are identified within five coarsening-upward sequence. Abundant hummocky cross stratification, low-angle inclined stratification, and swash cross stratification indicate dominance of wave processes. These nearshore sequences are overlain by offshore marine shales, which are thought to represent a major global eustatic sea-level rise in the latest Bathonian, continuing into the Early Callovian. During the transgression, deep portions of the basin developed anoxic bottom conditions, resulting in the deposition of bituminous black shales. The combined effects of basinal subsidence and eustatic sea-level rise resulted in a rapid rate of transgression which exceeded that of sedimentation; ca. 110 cm/Ka. </p> <p> Five ammonite associations date the Tecocoyunca Group as Upper Bathonian (Retrocostatum Zone) to Lower Callovian (Calloviense Zone). Biogeoqraphic affinity of the ammonite fauna is mostly Andean with signicant west-Tethyan/mediterranean elements and a few endemic species. The ammonite faunas show: 1) a rapid faunal replacement, 2) shell morphology trends, and 3 ) varying degrees of endemism/cosmopolitanism, all in relation to sea level variation. </p> <p>Biostratiqraphy and lithostratigraphy of the Tecocoyunca Group suggest that: 1) the Mixteca terrane had a paleoposition, during the Middle Jurassic, near the Pacific opening of the Hispanic Corridor (proto-AtlanticJ, 2) the Hispanic corridor provided marine connections between the eastern Pacific Ocean and the western Tethys Sea, and 3) preponderance near shore sediments suggests close proximity to the Andes of South America. </p> / Thesis / Master of Science (MS)

Les coccolithophoridés sont des algues marines photosynthétiques et planctoniques qui produisent des plaques micrométriques de carbonate de calcium (CaCO3) appelés coccolithes. Ces algues sont apparues il y 210 Ma et produisent actuellement la majeure partie du CaCO3 dans les océans modernes, jouant ainsi un rôle majeur dans le cycle du carbone. Cependant, l’émergence de la production de CaCO3 océanique par les coccolithophoridés au cours du Jurassique, ainsi que son impact sur le cycle du carbone, restent très mal compris. Cette étude s’est donc focalisée sur une période du Jurassique Moyen (Bajocien inférieur, -170 Ma) enregistrant la diversification de Watznaueria, un genre de coccolithophoridé qui a ensuite dominé la production de CaCO3 océanique pendant plus de 80 Ma. L’analyse des assemblages de coccolithes du Jurassique Moyen du Portugal et du sud de la France, réalisée à l’aide d’une méthode de reconnaissance automatique appliquée pour la première fois aux coccolithes du Jurassique, a permis de quantifier l’importance de cette période de diversification sur la production de CaCO3 pélagique. En outre, la durée de cet intervalle clé a été réévaluée grâce à l’analyse cyclostratigraphique des séries sédimentaires du Sud de la France. Les variations de production de CaCO3 pélagique ainsi reconstituées ont été comparées aux perturbations du cycle du carbone enregistrées par les rapports des isotopes du carbone, et indiquent un lien probable avec une augmentation marquée de la fertilité des océans. Par ailleurs, l’analyse paléontologique montre que cette diversification correspond à l’apparition successive de différentes espèces vraisemblablement opportunistes du genre Watznaueria. Enfin, les flux obtenus de CaCO3 pélagiques, largement inférieurs à ceux observés dans les océans actuels, semblent insuffisants pour avoir eu une influence significative sur le cycle global du carbone du Jurassique Moyen. / Coccolithophorids are photosynthetic and planktonic marine algae that produce micrometric calcium carbonate (CaCO3) platelets called coccoliths. These algae appeared about 210 Ma ago and produce today most of the CaCO3 in the modern oceans, hence playing a major role in the carbon cycle. Nevertheless, the onset of oceanic CaCO3 production by these organisms during the Jurassic and its impact on carbon cycling remain poorly understood. This study therefore focused on the Middle Jurassic interval (Early Bajocian, -170 Ma) which records the diversification of Watznaueria, an evolutionary important coccolith genus that subsequently dominated oceanic CaCO3 production for more than 80 Myr. The analysis of coccolith assemblages from the Middle Jurassic of southern France and Portugal, based on an automaticcoccolith recognition device used for the first time on Jurassic coccoliths, allowed quantifying the impact of this diversification on CaCO3 production. In addition, the duration of this key interval has been revaluated by the cyclostratigraphic analysis of sedimentary strata from southern France. The reconstructed changes in CaCO3 production were compared to carbon cycle perturbations recorded by carbon isotope ratios and indicate a probable link with a marked increase of ocean fertility. Besides, paleontological analyses show that this diversification episode correspond to the successive appearance of different, probably opportunistic Watznaueria species. The obtained fluxes of pelagic CaCO3 production, by far lower than those recorded in modern oceans, seems too low to have significantly impacted theMiddle Jurassic carbon cycle.

The late Middle Jurassic (Callovian) Entrada Sandstone has been divided into two general facies associations consisting primarily of eolian sandstones in eastern Utah and "muddy" redbeds in central Utah. Sedimentary structures within the redbed portion are explained by the interfingering of inland sabkha, alluvial, and eolian depositional systems. A complete succession from the most basinward facies to the most terrestrial facies in the Entrada Sandstone consists of inland sabkha facies overlain by either alluvial or eolian facies. Where both alluvial and eolian facies interfinger, alluvial facies overlain by eolian facies is considered a normal succession. Sequence boundaries, often identified by more basinward facies overlying more landward facies, are observed in the Entrada Sandstone and are extrapolated for the first time across much of Utah, including both the eolian-dominated and redbed-dominated areas. Using these sequence boundaries as well as recent tephrochronologic studies, three time correlative surfaces have been identified in the Entrada. Based on the facies interpretations at each surface, five paleogeographic reconstructions and five isopach maps have been created, illustrating two major intervals of erg expansion and the location of the Jurassic retroarc foreland basin's potential forebulge. Eolian (erg-margin) sandstones pinch-out into muddy redbeds creating combination traps, as evidenced by dead oil (tar) and bleached eolian sandstone bodies within the Entrada. The Entrada Sandstone is a world-class analog for similar systems, such as the Gulf of Mexico's Norphlet Sandstone, where eolian facies grade into muddy redbed facies.

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.