Dissertations / Theses on the topic 'Northeast Santos basin, Brazil'

Le principal objectif de cette étude est de mieux comprendre et de quantifier les paramètres et les processus de contrôle de la morphologie et de l’évolution stratigraphique du nord du bassin de Santos pour les derniers 49,5 my. Il s’agit de déconvoluer le signal climatique et tectonique dans l’enregistrement sédimentaire à travers de l’analyse sismique à diverses résolutions (~7-8 s et ~400 ms de penetration), de l’analyse lithologique et le calage chrono stratigraphique des limites de séquence majeures, à partir de 19 forages industriels. La modélisation stratigraphique par Dionisos combinée à nos observations nous a permis de quantifier les paramètres majeurs qui vont contrôler l’architecture sédimentaire à différentes échelles de temps. 9 séquences stratigraphiques sont ainsi identifiées et regroupées en 3 mégaséquences (Mégaséquences A, B et C): (i) La Mégaséquence A est caractérisée par des systèmes deltaïques qui viennent remplir l’espace d’accommodation créé par le fluage du sel vers le bassin entre la baie de Guanabara et Cabo Frio. Le flux sédimentaire qui la nourrit est mis en relation avec le paléo fleuve du Paraíba do Sul qui se deplace vers le bassin de Campos à la fin du development de la Mégaséquence et resulte dans une drastique reduction des flux du bassin de Santos; (ii) La Mégasequence B est caractérisée par la rétrogradation de tous les systèmes sédimentaires comme une réponse directe à la diminution des flux sédimentaires. Cette megasequence est aussi caracterisée par l’implantation des depots contouritiques entre 30 et 21 Ma, problablement liés à des changements dans la circulation oceanique dû a l’ouverture de la passage de Drake et de la Tasmanie (entre 37 et 28 Ma); (iii) La Mégasequence C est caractérisée par une progradation et le déplacement des offlap breaks de 70 km vers l’océan, depuis les derniers 11.5 my comme réponse de l’augmentation de flux sédimentaire qui caractérise le passage à des cycles glacio-eustatiques marqués dans le Quaternaire
The main objective of this study is to better understand and to quantify experimentally the main parameters that control the geomorphological and stratigraphic evolution of the Cenozoic sedimentary succession of the northeast Santos basin, Brazil, in the last 49.5 my. For this purpose, a variety of combining methologies were used, such as: seismic analysis of a dataset composed of different resolution levels (~7-8 s and ~400 ms penetration), chronostratigraphic and lithological data from 19 exploratory wells and stratigraphic modeling. Seismic analysis and stratigraphic modelling led to the identification of 9 main stratigraphic sequences that could be grouped into 3 megasequences (Megasequences A, B and C): (i) Megasequence A is characterized by deltaic features developed into a ramp feature located between Guanabara Bay and Cabo Frio. The formation of this delta resulted in a sedimentary overcharge that induced the basinward salt migration. The sedimentary input that feeds this delta was interpreted as related to an ancient Paraíba do Sul River that diversion to the Campos basin at the end of the megasequence development, resulting in a dramatically reduce the sedimentary influxes into Santos basin; (ii) Megasequence B is characterized by the retrogradational trend of sedimentary systems that offset offlap break of surfaces developed at 30 and 21 Ma about 78 km landward. This megasequence is also characterized by the beginning of conturites deposition related to the changes of oceanic circulation due to the opening of Drake and Tasmanian passages; (iii) Megasequence C is characterized by progradational systems that resulted in the coastline shift about 70 km oceanwards, in the last 11.5 my. The dominant progradational trend of this sequence is interpreted as a response of the increase in the sedimentary influx rate intensified by the spectral characteristics and amplitude of the glacial-induced eustatic signal that characterizes the Quaternary period

Le principal objectif de cette étude est de mieux comprendre et de quantifier les paramètres et les processus de contrôle de la morphologie et de l’évolution stratigraphique du nord du bassin de Santos pour les derniers 49,5 my. Il s’agit de déconvoluer le signal climatique et tectonique dans l’enregistrement sédimentaire à travers de l’analyse sismique à diverses résolutions (~7-8 s et ~400 ms de penetration), de l’analyse lithologique et le calage chrono stratigraphique des limites de séquence majeures, à partir de 19 forages industriels. La modélisation stratigraphique par Dionisos combinée à nos observations nous a permis de quantifier les paramètres majeurs qui vont contrôler l’architecture sédimentaire à différentes échelles de temps. 9 séquences stratigraphiques sont ainsi identifiées et regroupées en 3 mégaséquences (Mégaséquences A, B et C): (i) La Mégaséquence A est caractérisée par des systèmes deltaïques qui viennent remplir l’espace d’accommodation créé par le fluage du sel vers le bassin entre la baie de Guanabara et Cabo Frio. Le flux sédimentaire qui la nourrit est mis en relation avec le paléo fleuve du Paraíba do Sul qui se deplace vers le bassin de Campos à la fin du development de la Mégaséquence et resulte dans une drastique reduction des flux du bassin de Santos; (ii) La Mégasequence B est caractérisée par la rétrogradation de tous les systèmes sédimentaires comme une réponse directe à la diminution des flux sédimentaires. Cette megasequence est aussi caracterisée par l’implantation des depots contouritiques entre 30 et 21 Ma, problablement liés à des changements dans la circulation oceanique dû a l’ouverture de la passage de Drake et de la Tasmanie (entre 37 et 28 Ma); (iii) La Mégasequence C est caractérisée par une progradation et le déplacement des offlap breaks de 70 km vers l’océan, depuis les derniers 11.5 my comme réponse de l’augmentation de flux sédimentaire qui caractérise le passage à des cycles glacio-eustatiques marqués dans le Quaternaire
The main objective of this study is to better understand and to quantify experimentally the main parameters that control the geomorphological and stratigraphic evolution of the Cenozoic sedimentary succession of the northeast Santos basin, Brazil, in the last 49.5 my. For this purpose, a variety of combining methologies were used, such as: seismic analysis of a dataset composed of different resolution levels (~7-8 s and ~400 ms penetration), chronostratigraphic and lithological data from 19 exploratory wells and stratigraphic modeling. Seismic analysis and stratigraphic modelling led to the identification of 9 main stratigraphic sequences that could be grouped into 3 megasequences (Megasequences A, B and C): (i) Megasequence A is characterized by deltaic features developed into a ramp feature located between Guanabara Bay and Cabo Frio. The formation of this delta resulted in a sedimentary overcharge that induced the basinward salt migration. The sedimentary input that feeds this delta was interpreted as related to an ancient Paraíba do Sul River that diversion to the Campos basin at the end of the megasequence development, resulting in a dramatically reduce the sedimentary influxes into Santos basin; (ii) Megasequence B is characterized by the retrogradational trend of sedimentary systems that offset offlap break of surfaces developed at 30 and 21 Ma about 78 km landward. This megasequence is also characterized by the beginning of conturites deposition related to the changes of oceanic circulation due to the opening of Drake and Tasmanian passages; (iii) Megasequence C is characterized by progradational systems that resulted in the coastline shift about 70 km oceanwards, in the last 11.5 my. The dominant progradational trend of this sequence is interpreted as a response of the increase in the sedimentary influx rate intensified by the spectral characteristics and amplitude of the glacial-induced eustatic signal that characterizes the Quaternary period

It is recognised that some proportion of South American large-scale topography has been generated by convection within the Earth's mantle. Yet, spatial and temporal patterns of dynamic topography remain poorly understood. Variation of present-day dynamic topography can be mapped in the oceans by calculating residual depths with respect to the well-known age-depth relationship. Along the margins abutting South America, anomalies with amplitudes of $\pm1$ km and wavelengths of $\sim10^{3}$ km are observed. Onshore, dynamic topography is investigated by analysing a range of disparate datasets. Positive long-wavelength free-air gravity anomalies and slow shear-wave mantle velocities correlate with high plateaux of the Borborema Province and the Central Andean Altiplano. Admittance analyses of these regions are used to gauge dynamic support. Admittance of $ > 20$ mGal km$^{-1}$ at wavelengths $ > $ 500 km suggests partial dynamic support. In this context, inverse modelling of longitudinal river profiles is applied to retrieve a continental-scale uplift history. Erosional parameters are calibrated against an independently derived uplift history of the Borborema Province that reveals uplift in the last 30 Ma. Results suggest that the bulk of South American regional topography grew during Cenozoic times. In the Central Andean Altiplano and Southern Patagonia, most uplift occurred in the last 20 Ma. In both areas, widespread Cenozoic magmatism suggests that youthful uplift might be related to asthenospheric upwelling. Uplift histories are used to predict sediment flux to the Amazon Fan, which reveals that onset of the delta is a direct consequence of intensified Andean uplift. Analysis of the Parna\'iba cratonic basin of northeast Brazil is carried out to evaluate long-term evolution of vertical motions and to understand the mechanisms driving this basin's subsidence. Joint interpretation of a deep seismic reflection profile that traverses the basin and receiver function analyses reveal a 3 km thick basin underlain by three crustal blocks. Moho depths of 38--43 km are observed beneath the Amazon craton west of the basin, whereas depths of 35 km are found underneath the Borborema Province to the east. The Moho is located at 38--42 km depth beneath the basin. Stratigraphic architecture from shallow seismic reflection profiles reveals undisturbed deposition between Palaeozoic and Mesozoic times. Rift-type structures are locally imaged. Subsidence analysis reveals thermally-driven subsidence with thermal time constants of $\sim$ 70--80 Ma. Assessment of crustal thickness variations indicates that minimal extension of up to 80 km, with small stretching factors (up to 1.15), is plausible beneath Parna\'iba. One- and two-dimensional strain rate histories suggest that pre-Silurian rifting followed by thermal subsidence is possible if a minimum of 1 km of syn-rift deposition occurred. Basin-wide erosional unconformities are observed throughout the sedimentary section and correlate with departures from long-term subsidence trends. These steps are interpreted as transient uplift events that led to development of ephemeral landscapes, suggesting that dynamic topography could have played a role in the evolution of this Phanerozoic basin.

Cratonic basins cover more than 10% of Earth's continental surface area, yet their origin remains enigmatic. In this thesis a suite of new and legacy geophysical and geological data are integrated to constrain the origin of the Parnaíba basin, a cratonic basin in Northeast Brazil. These data include a 1400 km long, deep (20 s two-way travel time) seismic reflection profile, five +/- 110 km offset wide-angle split-spread receiver gathers, gravity anomaly, and well data. In the centre of the basin, the depth to pre-Paleozoic basement is ~ 3.3 km, a zone of midcrustal reflectivity (MCR) can be traced laterally for ~ 250 km at depths between 17-25 km and Moho depth is ~ 42 +/- 2 km. Gravity and P-wave modelling suggests that the MCR represents the upper surface of a high density (2985 kg m³) and V_p (6.7 - 7.0 km s^-1) lower crustal body, likely of magmatic origin. Backstripping of well data shows a concave up decreasing tectonic subsidence, similar in form to that commonly observed in rift-type basins. It is shown, however, that the seismic and gravity data are inconsistent with an extensional origin. It is shown that an intrusive body in the lower crust that has loaded and flexed the surface of the crust, combined with sediment loading, provides a satisfactory fit to the observed gravity anomaly, sediment thickness and basin shape. A buried load model is also consistent with seismic data, which suggest that the Moho is as deep or deeper beneath the basin centre than its flanks and accounts for at least part of the tectonic subsidence through a viscoelastic stress relaxation that occurs in the lithosphere following load emplacement. Comparative analysis of the Michigan and Congo basins shows gravity data from these basins is also consistent with a lower crustal mass excess, while subsidence analysis shows viscoelastic stress relaxation may also contribute to their early subsidence histories. However, unlike Parnaíba, both of these basins appear to have been subjected to secondary tectonic processes that obscure the primary 'cratonic basin' subsidence signals. Parnaíba basin, therefore, offers an excellent record for the investigation of cratonic basin formation.

South Atlantic margins display significant variation in structural style along their length. An understanding of factors that influence this variation in structural style is a key component in any understanding of the evolution of the South Atlantic. The Santos basin is an obliquely rifted basin located offshore SE Brazil. Structures in the basin are thought to have been influenced by the reactivation of basement structures and/or fabrics during the onset of the Gondwana breakup. The onshore region adjacent to the Santos Basin offers the chance to test whether basement structures have played a significant role in influencing the initiation and development of syn-rift faults, dykes and fractures. Field and remote sensing studies of the onshore region and on the conjugate margin in Africa show the strong geometric and temporal link between major 135Ma dyke swarms and the development of faults and fractures. 3 structural domains are defined, and correlated with lineament domains from the African margin. Faults, dykes and fractures within the lineament domains in SE Brazil share consistent orientations as large scale morphotectonic lineaments. Brittle structures show orientations and kinematics that are consistent with regional E-W oriented transtension. Little evidence of basement influence can be seen at outcrop scale, although it is speculated that larger scale structures may be reactivated. Faults in the offshore basin share similar geometries to brittle structures onshore. As rifting progressed, and dyke intrusion ceased, NNE-SSW trending structures to the north of the basin ceased to be active, while N-S trending extensional faults continued to deform. N-S trending faults and fractures are also observed to cut dykes in the onshore region. The importance of understanding onshore geology when interpreting offshore basins is highlighted in this study, as is the need to integrate diverse datasets when trying to understand the complex influences on margin development.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
A riquÃssima assembleia fossilÃfera encontrada na FormaÃÃo Santana do CretÃceo da Bacia do Araripe, alberga uma grande quantidade de insetos fÃsseis, incluindo a ordem "Blattaria", especialmente no Membro Crato de idade Albiana-Aptiana. A alta taxa de preservaÃÃo destes organismos e das suas partes mais frÃgeis, como as asas, acontece graÃas ao ambiente lacustre e de baixa energia em que foram depositados. As asas, tambÃm denominadas por tÃgminas, possuem um padrÃo de nervuras que permite avaliar exatamente a sua importÃncia taxonÃmica no meio paleontomolÃgico. No presente trabalho à realizado um estudo taxonÃmico, onde sÃo descritas cinco novas espÃcies provenientes do calcÃrio laminado da porÃÃo superior do Membro Crato da Mina Pedra Branca em Nova Olinda, CearÃ. Os exemplares descritos encontram-se incluÃdos, um no gÃnero Mesoblattinopsis Pinto 1989, um no gÃnero Blattulopsis Pinto 1990 e trÃs no gÃnero Mesoblattina Geinitz 1880. Para isso e para uma melhor organizaÃÃo dos critÃrios que permitiram incluÃ-las nos gÃneros mencionados anteriormente foram elaboradas tabelas que mostram as principais diferenÃas entre os exemplares e as espÃcies jà descritas.
A riquÃssima assembleia fossilÃfera encontrada na FormaÃÃo Santana do CretÃceo da Bacia do Araripe, alberga uma grande quantidade de insetos fÃsseis, incluindo a ordem "Blattaria", especialmente no Membro Crato de idade Albiana-Aptiana. A alta taxa de preservaÃÃo destes organismos e das suas partes mais frÃgeis, como as asas, acontece graÃas ao ambiente lacustre e de baixa energia em que foram depositados. As asas, tambÃm denominadas por tÃgminas, possuem um padrÃo de nervuras que permite avaliar exatamente a sua importÃncia taxonÃmica no meio paleontomolÃgico. No presente trabalho à realizado um estudo taxonÃmico, onde sÃo descritas cinco novas espÃcies provenientes do calcÃrio laminado da porÃÃo superior do Membro Crato da Mina Pedra Branca em Nova Olinda, CearÃ. Os exemplares descritos encontram-se incluÃdos, um no gÃnero Mesoblattinopsis Pinto 1989, um no gÃnero Blattulopsis Pinto 1990 e trÃs no gÃnero Mesoblattina Geinitz 1880. Para isso e para uma melhor organizaÃÃo dos critÃrios que permitiram incluÃ-las nos gÃneros mencionados anteriormente foram elaboradas tabelas que mostram as principais diferenÃas entre os exemplares e as espÃcies jà descritas.

Esta tese apresenta o registro de variações paleoceanográficas na superfície e em oceano profundo na porção oeste do Atlântico Sul, através de evidências de nanoplâncton calcário, durante os últimos 200.000 anos. Os principais parâmetros avaliados foram relativos à paleoprodutividade primária, através de estimativas de abundância e taxa de acumulação do nanoplâncton calcário, índices paleoceanográficos de produtividade, variação de carbonato de cálcio, contribuição relativa das espécies de nanoplâncton para o carbonato de cálcio total e análises de dados geoquímicos complementares. Os dados derivam de três testemunhos coletados na Bacia de Santos entre 1900 e 2200 metros de profundidade. Os resultados demonstram que as mudanças paleoceanográficas observadas no período analisado devem estar relacionadas, concomitantemente, a variações na dinâmica do oceano na camada superficial e em oceano profundo. As evidências de paleoprodutividade primária e a subsequente deposição do nanoplâncton calcário apontam que ambas são dependentes de condições favoráveis em superfície e no fundo, respectivamente. Estas condições ocorreram durante o período de aquecimento das águas superficiais no oeste do Atlântico Sul e a retração de águas profundas de origem sul devido à intensificação da célula de revolvimento meridional do Atlântico. Os últimos 200.000 anos foram divididos em sete intervalos definidos pela variação de paleoprodutividade primária com base no registro de nanoplâncton calcário.
This thesis presents a view of the paleoceanographic changes that occurred in the surface and deep ocean in the western South Atlantic by means of calcareous nannoplankton during the last 200,000 years. Data was obtained from three sediment cores collected in the Santos Basin between 1900 and 2200 meters water depth. Estimates of primary paleoproductivity from calcareous nannoplankton abundance and accumulation rates, paleoproductivity proxies calcium carbonate content, the relative contribution of nannoplankton species to total calcium carbonate and complementary geochemical data analyzes were performed. The results demonstrate that paleoceanographic changes observed in the analyzed period may be related to changes in ocean dynamics at surface and deep ocean. Primary paleoproductivity record and the subsequent calcareous nannoplankton deposition indicate that these are dependent on surface and bottom conditions, respectively. These conditions were recorded during sea surface temperature warming in the western South Atlantic and retraction of southern-sourced deep waters due to strengthening of the Atlantic meridional overturning circulation. The last 200,000 years were divided into seven intervals defined by the changes in primary paleoproductivity record of calcareous nannoplankton.

The dissertation examines the interaction between basement tectonics, salt tectonics and sedimentation during the Late Cretaceous basement reactivation in the center of the Santos Basin. The study area is a seismic volume 60 x 30 km² in area, augmented by 2D regional seismic lines. The results of seismic interpretation and structural restorations revealed important inversions in the Late Cretaceous, including inversion of an NNE-oriented aborted rift segment known as Merluza Graben. The following tectono-stratigraphic evolution was inferred. During the Albian, basin subsidence and differential loading by the overburden caused salt to flow basinwards. In the Late Turonian, intraplate compression resulted in uplift of the onshore and proximal areas of the Santos Basin and in a newly recognized basement inversion in deep water. ENE and NNE oriented structures were reactivated. The uplift exposed the Turonian shelf and a new shelf began to prograde. The first shelves were narrow (~25 km wide) but enlarged to 60 km in the Santonian. Salt influenced the position of the shelf break and the progradation pattern of the shelf margin. Because of the continuous accommodation space provided by salt withdrawal underneath the sedimentary wedge, the shelf margin aggraded until underlying salt welded, after which the shelf prograded to a position around 50 km to the east of the present-day shelf break. Deformation peaked in the Late Santonian when the shelf was widest, the rate of progradation of the shelf margin was anomalously high, and transtension along the borders of the Merluza Graben allowed Late Santonian magma to intrude. Salt acted as a partial seal, causing a large part of the magma to spread beneath it. Some magma formed sills inside the evaporitic layer, intruding zones of dilation in the salt. Magma also followed the top of the evaporitic layer and intruded salt-related faults as dikes. These dikes supplied sills in the overburden and extrusive flows emerged on the Late Santonian seafloor from ENE-striking transtensional zones. Right-lateral reactivation of the Merluza Graben borders slightly compressed the graben, which favored sill injection in Coniacian/Santonian strata. Tectonic activity diminished towards the end of the Cretaceous.
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The Lower Cretaceous tectonosequence constitutes a major chronostratigraphic interval in the Recôncavo Basin, Northeast Brazil. It encompasses a time span of ca. of 24 Ma and forms a continental sedimentary package that exceeds 5 km in thickness within its depocenters. The tectonosequence is bounded by two basinwide unconformities, the rift onset unconformity at its base and the breakup unconformity at its top. The basal deposits of the tectonosequence characterize transitional rift conditions. The bulk of the succession constitutes the record of the rift phase in the basin. Biostratigraphy in the Recôncavo Basin is based on nonmarine ostracods. The tectonosequence encompasses ostracod zones NRT 002 through NRT 009. Tectonic, sedimentologic, and paleoecologic characteristics permit the recognition of six tectono-depositional intervals within the tectonosequence. Tectono-depositional intervals cover a time span between 2 Ma and 7.5 Ma, and their boundaries are distinct marker beds. Lithologic, paleontologic, and geochemical characteristics of the marker beds suggest low sediment input at the time of their deposition. Tectonic and/or paleoclimatic changes may account for phases of marker bed creation. Within tectono-depositional inteivals II, IV, and V sedimentary cyclicity occurs. Sedimentary cycles spanning tens to hundreds of thousands years are termed tectono-depositional episodes. Such an episode is comparable in scale with a parasequence, and is also bounded by marker beds reflecting flooding events. Depositional systems within the tectonosequence show a change from lacustrine-dominated sedimentation at the base to fluvial-dominated deposition at the top. Reservoir potential increases toward the top of the tectonosequence, source rock and sealing conditions, however, follow the opposite path. The bulk of known hydrocarbon accumulations in the Recôncavo Basin occurs at the prerift/rift interface. Accumulation rate estimates show increasing values toward the top of the tectonosequence. This may be related to a better integration of the drainage system that fed into the basin and removal of possible structural barriers located along the basin's margins. Analysis of the sedimentary record of the tectonosequence suggests, besides tectonism, paleoclimate was an important mechanism controlling facies distribution and evolution.
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Tese de mestrado, Geologia (Estratigafia, Sedimentologia e Paleontologia) Universidade de Lisboa, Faculdade de Ciências, 2019
This work aims to better understand the Pre-Salt Barra-Velha Formation lacustrine carbonates and their depositional setting and diagenetic evolution in a specific zone of Santos Basin, Brazil. A multi-scale workflow based on well core analysis and its relation with well log data and stratigraphic seismic interpretation was used to provide a better understanding of facies distribution and depositional cycles, with focus on the Upper Sag unit. The outcomes from the different tasks allowed to develop a conceptual depositional model with application on reservoir characterization, representing a generic regional propose applicable to the Pre-Salt carbonates in the studied area. The results from the six described wells demonstrate high depositional cyclicity, indicating mainly a shallow water environment, being possible to define a generic facies sequence based on base-level position and energy variations. Facies successions identification allowed the recognition of sequence boundaries, which demonstrated that changes in base-level and accommodation space were responsible for different facies deposition. The integration of multiscale data with seismic interpretation demonstrate a progressive basin fill, starting north and gradually reaching structural higher positions. Paleogeomorphology strongly controlled sediment deposition, as different depositional environment conditions were observed in different structural positions, with high base-level position and low energy facies being mainly recognized in structural lows and low base-level position and high energy facies being mostly identified in structural highs. It was also recognized an affinity of diagenetic processes with paleogeomorphology, with fluid circulation having a major impact in structural low positions resulting in porosity reduction processes, while in structural high positions, porosity generation or enhancing processes tend to be more frequent. The understanding of depositional environments retrieved from this study will enhance the geological understanding of Santos Basin depositional setting and may assist on hydrocarbon exploration by providing a more robust reservoir characterization, from a geological point of view.

This research investigates the character and significance of shelf-edge deltas within the sedimentary source-to-sink system, and how variability at the shelf edge leads to different styles of deep-water deposition. Because the shelf-edge represents one of the key entry points for terrigenous sediment to be delivered into the deep water, understanding of the sedimentary processes in operation at these locations, and the character of sediment transported through these deltas is critical to understanding of deep-water sedimentary systems. The research was carried out using three datasets: an outcrop dataset of 6000 m of measured sections from the Permian-Triassic Karoo Basin, South Africa, a 3D seismic data volume from the Eocene Northern Santos Basin, offshore Brazil and a dataset of 29 previously published descriptions of shelf-edge deltas from a variety of locations and data types. The data presented highlight the importance of sediment instability in the progradation of basin margins, and deep-water transport of sediment. The strata of the Karoo Basin shelf margin represent river-dominated delta deposits that become more deformed as the shelf-edge position is approached. At the shelf edge, basinward dipping, offlapping packages of soft-sediment-deformed and undeformed strata record repetitive collapse and re-establishment of shelf-edge mouth bar packages. The offlapping strata of the Karoo outcrops record progradation of the shelf margin through accretion of the shelf-edge delta, for over 1 km before subsequent transgression. The Eocene Northern Santos Basin shelf margin, in contrast, exhibits instability features which remove kilometers-wide wedges of the outer shelf that are transported to the basin floor to be deposited as mass-transport packages. In this example, shelf-edge progradation is achieved through „stable. accretion of mixed turbidites and contourites. The data also emphasize the importance of the role of shelf-edge delta processes in the delivery of sediment to the basin floor. A global dataset of 29 examples of shelf-edge systems strongly indicates that river domination of the shelf-edge system (as read from cores, well logs or isopach maps) serves as a more reliable predictor of deep-water sediment delivery and deposition than relative sea level fall as traditionally read in shelf-edge trajectories or sequence boundaries.
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