scholarly journals Seismic expression of depositional elements associated with a strongly progradational shelf margin: northern Santos Basin, southeastern Brazil

2016 ◽  
Vol 46 (4) ◽  
pp. 585-603 ◽  
Author(s):  
Fábio Berton1* ◽  
◽  
Fernando Farias Vesely
Keyword(s):  
Mass Transport ◽  
Progressive Increase ◽  
Seismic Facies ◽  
Southeastern Brazil ◽  
Submarine Channels ◽  
Base Level ◽  
Equilibrium Profile ◽  
Mass Transport Deposits ◽  
Shelf Margin ◽  
Depositional Elements

ABSTRACT: Seismic facies analysis and seismic geomorphology are important tools for the analysis of depositional elements in subsurface. This paper aimed to investigate the character and genesis of depositional elements and erosive features associated with an Eocene progradational shelf margin in northern Santos Basin. Identified seismic facies are interpreted as shelf-margin deltas/shoreface deposits, tangential (oblique) clinoforms, sigmoidal clinoforms, topset reflectors, mass-transport deposits and turbidites. These facies are grouped into four associations representing periods of relatively constant environmental conditions. Association 1 is composed of shelf-margin deltas/shoreface deposits, tangential clinoforms and extensive sand-rich turbidites disposed as submarine channels and frontal splays. A progressive increase in clinoform angle within this association has been identified, culminating in high-relief sigmoidal clinoforms with less voluminous turbidites of facies association 2. Association 3 is composed by subparallel to divergent topset reflectors, interpreted as continental to shelfal deposits placed during base-level rises. These are always truncated basinward by slump scars, formed as a consequence of sediment overload at the shelf margin during aggradations. Association 4 is composed of sigmoidal clinoforms, mass-transport deposits and turbidites. Early clinoforms are steeper as a consequence of the topography of the slump scars. Subsequently, dip angles become progressively gentler as the system approach to the equilibrium profile. The steep physiography was favorable for canyon incision, which played an important role in turbidite deposition. Mass-transport deposits, formed subsequent to slope collapse, are composed of mud-rich diamictites, and show strong internal deformation.

Assessment of the effect of mass-transport deposits on fault propagation in Penobscot area, offshore Nova Scotia

2018 ◽  
Vol 477 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Tuviere Omeru ◽  
Samson I. Bankole ◽  
Byami A. Jolly ◽  
Obafemi S. Seyi ◽  
Joses B. Omojola
Keyword(s):  
Nova Scotia ◽  
Mass Transport ◽  
Three Dimensional ◽  
Seismic Facies ◽  
Thickness Variation ◽  
Fault Propagation ◽  
Seismic Profiles ◽  
History Of ◽  
Throw Distance ◽  
Mass Transport Deposits

AbstractThree-dimensional (3D) seismic data and well logs from the Penobscot area, located within the Scotian Basin offshore Nova Scotia, are used to assess the role of mass-transport deposits (MTDs) on fault propagation. Four MTDs characterized by chaotic seismic facies were mapped, with the earliest hosted by the Late Cretaceous–Recent Dawson Canyon Formation and latest three hosted by the Banquereau Formation. Two types of faults were also mapped. R-faults are regional faults that cut across all the interpreted MTDs in the study area, while P-faults are polygonal faults that cut across MTDs 2 and 3 but tip out at the basal surfaces of MTDs 4 and 2. Representative seismic profiles and isochron maps of the MTDs and throw–depth (T–z) and throw–distance (T–x) plots allows us to distinguish the families and propagation history of the faults. Our results show that fault propagation is not affected by the presence or thickness variation of MTDs, and is also unaffected by lithological contrast in the Penobscot area of the Nova Scotian Shelf.

scholarly journals Application of seismic stratigraphy in reservoir characterisation: a case study of the passive margin deposits of the northern Orange Basin, South Africa

2020 ◽  
Author(s):  
Chris Adesola Samakinde ◽  
Jan Marinus Van Bever Donker ◽  
Ray Durrheim ◽  
Musa Manzi
Keyword(s):  
South Africa ◽  
Mass Transport ◽  
Gamma Ray ◽  
Sedimentary Basins ◽  
Seismic Stratigraphy ◽  
Passive Margin ◽  
Seismic Facies ◽  
Depositional Sequences ◽  
Seismic Reflectors ◽  
Mass Transport Deposits

AbstractThe Barremian-Cenozoic depositional sequences in the northern Orange Basin, SW, South Africa, were investigated using the principles of seismic stratigraphy to understand the interplay of tectonics and sedimentary processes in the distribution of potential hydrocarbon reservoirs. A seismic stratigraphic workflow (seismic sequence, seismic facies and lithofacies analysis) was completed by utilising three seismic lines (L1, L2 and L3) tied to Wireline data (gamma, checkshots and sonic) in two exploration wells (A1 and A2). Seven depositional sequences were mapped followed by the creation of lithofacies log interpreted from the gamma-ray log (GR) by setting maximum GR value at 60 API for Sandstone, 60–100 API for Siltstone and above 100 API for Shale. Six seismic facies units are recognised based on internal geometry and configurations of the seismic reflectors; Tangential-Oblique (SF1), Hummocky (SF2), Wavy-Parallel (SF3), Chaotic (SF4), Sub-parallel/parallel (SF5) and Divergent (SF6). SF4 is dominant within the Barremian-Aptian sequence and expressed in an incised valley fill, suggesting mass transport deposition accompanied by strong hydrodynamic conditions. Evidence of sedimentary basins progradation is seen within the Late-Albian-Turonian sequences, because of the occurrences of SF2, SF6 and SF 4 facies. SF5 facies is prominent in the Maastrichtian/Campanian sequence, indicating that the deposition of sediments may have been accompanied by uniform margin subsidence after the Late-Cretaceous uplift of the Africa margin. The occurrence of SF1 and SF4 facies within the Cenozoic sequence indicates terrigenous pro-deltaic deposits and mass transport deposits, respectively. Further results from seismic-lithofacies modelling reveal that sand deposits of Barremian-Aptian (SF4 facies unit) and Albian sequences (SF2 and SF6 facies units) are potential stratigraphic reservoirs in this part of the basin.

scholarly journals Geostatistical characterization of internal structure of mass-transport deposits from seismic reflection images and borehole logs

2019 ◽  
Vol 221 (1) ◽  
pp. 318-333
Author(s):  
Jonathan Ford ◽  
Angelo Camerlenghi
Keyword(s):  
Mass Transport ◽  
Internal Structure ◽  
Seismic Reflection ◽  
Slope Failure ◽  
Random Medium ◽  
Seismic Facies ◽  
Strain History ◽  
Borehole Data ◽  
Mass Transport Deposits ◽  
Scale Length

SUMMARY Seismic reflection images of mass-transport deposits often show apparently chaotic, disorded or low-reflectivity internal seismic facies. The lack of laterally coherent reflections can prevent horizon-based interpretation of internal structure. This study instead inverts for geostatistical parameters which characterize the internal heterogeneity of mass-transport deposits from depth-domain seismic reflection images. A Bayesian Markov Chain Monte Carlo inversion is performed to estimate posterior probability distributions for each geostatistical parameter. If the internal heterogeneity approximates an anisotropic von Kármán random medium these parameters can describe the structural fabric of the imaged mass-transport deposit in terms of lateral and vertical dominant scale lengths and the Hurst number (roughness). To improve the discrimination between vertical and lateral dominant scale lengths an estimate of the vertical dominant scale length from a borehole is used as a prior in the inversion. The method is first demonstrated on a synthetic multichannel seismic reflection image. The vertical and lateral dominant scale lengths are estimated with lower uncertainty when data from a synthetic borehole data are included. We then apply the method to a real data example from Nankai Trough, offshore Japan, where a large mass-transport deposit is imaged in a seismic profile and penetrated by a borehole. The results of the inversion show a downslope shortening in lateral scale length, consistent with progressive down-slope disaggregation of the mass-flow during transport. The dominant scale lengths can be used as a proxy for strain history, which can improve understanding of post-failure dynamics and emplacement of subacqueous mass-movements, important for constraining the geohazard potential from future slope failure.

scholarly journals RECOGNIZING LATE CRETACEOUS TO PALEOGENE CHANGES IN RELATIVE SEA LEVEL IN NORTHERN SANTOS BASIN, BRAZIL

2019 ◽  
Vol 37 (2) ◽  
Author(s):  
A.M. Garcia ◽  
C.A. Pires ◽  
D. Münch ◽  
I. F.P Carvalho ◽  
L.S Freitas ◽  
...  
Keyword(s):  
Sea Level ◽  
Higher Order ◽  
Seismic Facies ◽  
Relative Sea Level ◽  
Seismic Section ◽  
Basin Scale ◽  
System Tracts ◽  
Mass Transport Deposits ◽  
Order Sequence ◽  
Shelf Margin

ABSTRACT. The stratigraphy of the Santos Basin has become of great interest in the last decade because of the large oil accumulations in pre-salt (rift) and post-salt (drift) strata. Nevertheless, the most accepted stratigraphic models for the drift phase are only at a basin scale and can still be improved by more detailed work. In this paper we analyze an inline seismic section in the modern continental slope of the Santos Basin in order to describe the stratigraphy and to reconstruct relative-sea level (RSL) changes from the Campanian to the Eocene/Oligocene boundary. We mapped 40 seismic horizons, in which clinoform rollovers (former shelf margins) and stratal terminations were recognized. These data allowed for the construction of a chronostratigraphic chart and a RSL curve. The proposed stratigraphic chart displays three lower-order sequence sets comprising higher-order sequences including mostly alternating forced-regressive and normal-regressive system tracts, with the exception of three important transgressive episodes. Higher-order sequences above the intra-Maastrichtian unconformity exhibit low-angle ascending to descending shelf-margin trajectories and frequently truncated topsets, while aggradation was more important during Campanian to Maastrichtian. Expressive mass-transport deposits (chaotic seismic facies) at the bottomsets of some mapped horizons all match with forced-regressive episodes.Keywords: seismic interpretation, sequence stratigraphy, shelf-margin clinoforms.RESUMO. A Bacia de Santos tornou-se de grande interesse na última década devido às acumulações de petróleo no pré-sal (rifte) e pós-sal (deriva). No entanto, os modelos estratigráficos mais aceitos para a fase de deriva são em escala de bacia e podem ser incrementados por trabalhos de maior detalhe. Analisamos uma seção sísmica longitudinal no talude continental atual da bacia, a fim de descrever a estratigrafia e reconstruir mudanças do nível relativo do mar (NRM) do Campaniano ao limite Eoceno/Oligoceno. Quarenta horizontes sísmicos foram mapeados, nos quais margens da plataforma (clinoform rollovers) e terminações estratais foram reconhecidas. Esses dados permitiram a construção de um diagrama cronoestratigráfico e uma curva de variação do NRM. Identificou-se três conjuntos de sequências de menor ordem compreendendo sequências de ordem mais elevada, incluindo, na sua maioria, alternância entre regressão forçada e normal, com exceção de três importantes episódios transgressivos. As sequências de maior ordem acima da inconformidade intra-Maastrichtiano exibem trajetórias ascendentes de baixo ângulo a descendentes de margem de plataforma e topsets truncados, enquanto agradação foi mais importante entre o Campaniano e o Maastrichtiano. Depósitos de transporte de massa (fácies sísmicas caóticas) nos bottomsets de alguns horizontes mapeados associam-se com episódios de regressão forçada.Palavras-chave: interpretação sísmica, estratigrafia de sequências, clinoformas de margem de plataforma.

Shelf-derived mass-transport deposits: origin and significance in the stratigraphic development of trench-slope basins

2021 ◽  
pp. 1-36
Author(s):  
Barbara Claussmann ◽  
Julien Bailleul ◽  
Frank Chanier ◽  
Geoffroy Mahieux ◽  
Vincent Caron ◽  
...  
Keyword(s):  
Mass Transport ◽  
Mass Transport Deposits ◽  
Trench Slope

BIOINDICATORS OF SEA-LEVEL FLUCTUATIONS IN SOUTHEASTERN BRAZIL: NEW DATA AND METHODOLOGICAL REVIEW

Radiocarbon ◽  
2021 ◽  
pp. 1-15
Author(s):  
Julia Caon Araujo ◽  
Kita Chaves Damasio Macario ◽  
Vinícius Nunes Moreira ◽  
Anderson dos Santos Passos ◽  
Perla Baptista de Jesus ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Data Interpretation ◽  
Progressive Increase ◽  
Southeastern Brazil ◽  
Recrystallization Process ◽  
Sea Level Changes ◽  
Sea Level Fluctuations ◽  
Data Gap ◽  
Current Zero

ABSTRACT The vermetidae fossils of Petaloconchus varians, formed by calcium carbonate, associated with their radiocarbon ages, are the most accurate indicators of paleo sea level due to their restricted occupation in the intertidal zone in the rocky shore. However, the recrystallization of minerals can affect these age calculations and, consequently, the interpretation of the data. The aim of this study is to present new indicators of paleo sea-level changes in Southeast Brazil for the last 6000 years contributing to fill the data gap for the late Holocene. The influence of the recrystallization process was successfully resolved using the CarDS protocol, enabling the separation of the original aragonite fraction by density, prior to radiocarbon dating. This avoids the rejuvenation of ages and ensures greater efficiency for data interpretation. Paleo sea-level indicators were able to show a progressive increase in sea level up to the transgressive maximum of 4.15 m in 3700 BP years, followed by a regression to the current zero. This regression seems to have in addition, here we reinforce the reliability of the use of fossil vermetids as indicators of sea-level fluctuations.

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