Bruno Henrique de Moura Merss
Keywords: Mass-transport deposits; gravity-driven movements; sediment deformation.
Introduction
Underwater gravity-driven mass transport has an important role in shaping many continental margins (Butler and Turner 2010). Their products can result in reservoirs, seals and marker beds for the oil industry and their processes can affect human activity by generating tsunamis and destabilizing coastal and subsea infrastructure such as oil platforms, ports and telecommunication cables (Fukuda et al.
2015). The development of three-dimensional (3D) seismic data has been shown to be an excellent tool when studying large-scale folds and thrust belts generated by gravity-driven movements, especially when the focus is the linkage between proximal (extensional) and external (contractional) domains. This study will focus on applying high resolution seismic to understand how the internal structural geometry is spread over Maricá mass-transport complex (MTC) (Figure 1) and how this geometry varies across proximal, translational and external domains via 3D characterization.
Figure 1. Map of south-southeast Brazil with indication of Santos Basin and the area of study. (Modified from Carlotto and Rodrigues 2009; Berton and Vesely 2016).
Geological context, previous studies and foundational theory
Santos Basin is located in the coastal region of four states: Rio de Janeiro, São Paulo, Paraná and Santa Catarina (Figure 1). Currently the basin represents almost 50% of Brazilian gas and oil production (ANP 2018), due to the pre-salt petroleum play. According to Moreira et al. (2007), the basin can be divided into three chrono-lithostratigraphic supersequences: rift, post-rift and drift. The rift supersequence has three formations: Camboriú (basalts), Piçarras (sandstones and lacustrine mudstones) and Itapema (mudstones). The post-rift supersequence includes Barra Velha formation
(carbonates and shales) and Ariri formation (evaporites). Lastly the drift supersequence, which includes Camburi, Frade and Itamambuca groups.
Underwater gravity-driven mass transports nomenclature has overlapping and differing meaning, as shown by Shanmugam (2016). This study will use the term “Mass-transport complex” (MTC) to include all kinds of gravity-induced or downslope deposits, with the exception of turbidites (Moscardelli et al.
2006; Nelson et al. 2011). A typical MTC model will have three domains: proximal, translational and external (Figure 2). The proximal domain is characterized by an extensive style; it is thin and has well organized sediments and it is common to find normal and listric faults. This region also has steep dips and escarpments (Nardin et al. 1979; Stow et al. 1996). The translational domain is the region between proximal and external domains and it is characterized by having remnant blocks with no deformation, also known as rafted or intact blocks (Bull et al. 2009). The external domain is identified by a compressional style with folding and thrusts, and thick units with a chaotic internal organization (Bull et al. 2009).
Figure 2. Schematic representation of a gravity-driven mass transport complex (MTC) showing the three domains and predominant structural characteristics. (Modified from Galloway and Hobday 1996).
The Maricá MTC was studied by Carlotto and Rodrigues (2009). It is a Maastrichtian mass-transport complex located in northern Santos Basin. It is 150m thick and has an area of 1015m². According to the authors, the MTC deposition was structured by elongated depressions controlled by N-S salt diapirs and it was triggered by sediment overload at the delta front.
Methods
The study development will be divided into three steps:
a) Literature review: compile studies about seismic, seismic stratigraphy and morphology (e.g. Bacon et al 2003; Alfaro et al. 2014; Nanda 2016;), mass-transport deposits and complexes (e.g. Frey-Martínez et al. 2005; Moscardelli et al. 2006), and kinematics (e.g. Bull et al. 2009; Alsop et al.
2017) to build a solid background on seismic interpretation and structural characterization using 3D seismic as an evaluative tool.
b) Identify and map the MTC internal structures: seismic data provided by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) through the Bank of Exploration and Production Data (BDEP) is going to be meticulously analyzed using OpendTect 6.2.0 by dGB Earth Sciences™.
This evaluation will primarily utilize two seismic attributes, shaded-relief and dip-steered coherency.
Shaded-relief uses a distant light source to measure the amount of variable light that would be illuminated by dipping seismic events, and this illumination displays 3D seismic data and topography as time slices, allowing for insight into the true geology (Barnes 2002, 2003, 2010). Dip-steered coherency is a method that combines local dip seismic events (dip-Dip-steered) and similarity
between adjacent traces (coherency) resulting in an accurate and powerful tool that provides enhanced visualization of planar structures (De Groot and Bril 2005; Brouwer 2009).
c) 3D characterization: after identification and mapping the MTC internal structures, 3D models will be constructed using OpendTect 6.2.0 to illustrate the internal structural architecture and variations within the MTC. It will also provide a visual representation showing the relationship between structures and lateral variations, and how this relationship differs along proximal, translational and external domains (e.g. Frey-Martínez et al. 2006; Scarselli et al. 2016)
Anticipated results
The complete 3D characterization will serve as a reference resource when studying deformed regions with outcrops lacking in quality and/or quantity providing foresight on internal structural architecture and style variation within the MTC. It will also provide information regarding structures’ lateral continuation, assisting future studies on outcrop MTCs, for example the Itararé Group, known for having mass-transport deposits and complexes but lacking in tridimensional outcrops.
Acknowledgements
The author would like to thank Universidade Federal do Paraná (UFPR), Programa de Pós-graduação em Geologia and Laboratório de Análise de Bacias/Basin Analysis Research Lab (LABAP) for the support.
References
Alraro E., Holz M. 2014. Seismic geomorphological analysis of deepwater gravity-driven depostis on a slope system of the southern Colombian Caribbean margin. Marine and Petroleum Geology, 57:294-311.Alsop G.I., Marco S., Tevi T., Weinberger R. 2017. Fold and thrust systems in Mass Transport Deposits.
Journal of Structural Geology, 94:98-115.
ANP (Agência Nacional do Petróleo, Gás Natural e Biocombustíveis. 2018. Boletim mensal da produção de petróleo e gás natural. Available in: <http://www.anp.gov.br/publicacoes/boletins-anp/2395-boletim-mensal-da-producao-de-petroleo-e-gas-natural>
Bacon M., Simm R., Redshaw T. 2003. 3-D Seismic Interpretation. Cambridge, Cambridge University Press, 234 p.
Barnes A.E. 2002. What a relief shade can be. AAPG Explorer, 8.
Barnes A.E. 2003. Shaded relief seismic attribute. Geophysics, 68(4):1281-1285.
Barnes A.E. 2010. Shining light on a shady situation. AAPG Explorer, 31:30-31.
Berton F., Vesely F.F. 2016. Seismic expression of depositional elements associated with a strongly progradational shelf margin: northern Santos Basin, southeastern Brazil. Brazilian Journal of Geology, 46(4):585-603.
Brouwer F. 2009. Creating a good steering cube <http://static.dgbes.com/images/PDF/
effectivedipsteeringworkflowusingbgsteering_primerodata.pdf>
Bull S., Cartwright J., Huuse M. 2009. A review of kinematic indicators from mass-transport complexes using 3D seismic data. Marine and Petroleum Geology, 26:1132-1151.
Butler R.W.H., Turner J.P. 2010. Gravitational collapse at continental margins: products and processes;
and introduction. Journal of the Geological Society, 167:569-570.
Carlotto M.A., Rodrigues L.F. 2009. O Escorregamento Maricá - anatomia de um depósito de fluxo gravitacional de massa do Maastrichtiano, Bacia de Santos. Boletim de Geociências da Petrobras, 18(1):51-67.
De Groot P., Brill B. 2005. The Open Source Model in Geoscience and OpendTect in Particular. In:
Society of Exploration Geophysics Technical Program Expanded Abstracts. p. 802-805.
Frey-Martínez J., Cartwright J., Hall B. 2005. 3D seismic interpretation of slump complexes: examples from the continental margin of Israel. Basin Research, 17:83-108.
Frey-Martínez J., Cartwright J., James D. 2006. Frontally confined versus frontally emergent submarine landslides: A 3D seismic characterisation. Marine and Petroleum Geology, 23:585-604.
Fukuda K., Suzuki M., Ito M. 2015. The origin and internal structures of submarine-slide deposits in a lower Pleistocene outer-fan succession in the Kazusa forearc basin on the Boso Peninsula of Japan.
Sedimentary Geology, 321:70-85.
Galloway W.E., Hobday D.K. 1996. Terrigenous clastic depositional systems: applications to fossil fuel and groundwater resources. 2.ed. Berlin, Springer-Verlag, 489 p.
Moreira J.L.P., Madeira C.V., Gil J.A., Machado M.A.P. 2007. Bacia de Santos. Boletim de Geociências da Petrobras, 15(2): 531-549.
Moscardelli L., Wood L., Mann P. 2006. Mass-transport complexes and associated processes in the offshore area of Trinidad and Venezuela. AAPG Bulletin, 90(7):1059-1088.3
Nanda N.C. 2016. Seismic data interpretation and Evaluation for hydrocarbon exploration and production: a practitioner's guide. Springer, 224 p.
Nardin T.R., Hein J.F., Gorsline D.S. Edwards B.B. 1979. A review of mass movement processes, sediment and acoustic characteristics, and contrasts in slope and base-of-slope systems versus canyon-fan-basin floor systems. Society of Economic Paleontologists and Mineralogists Special Publication, 27:61-73.
Nelson C.H., Escutia C., Damuth J.E., Twichell D.C. 2011. Interplay of mass-transport and turbidite-systems deposits in different active tectonics and passive continental margin settings: external and local controlling factors In: Shipp R.C., Weimer P., Posamentier H.W. (eds.). Mass-transport deposits in deepwater settings. SEPM - Special publication 96, Tulsa, Society of Sedimentary Geology, p. 39-66.
Scarselli N., McClay K., Elders C. 2016. Seismic geomorphology of cretaceous megaslides offshore Namibia (Orange Basin): Insights into segmentation and degradation of gravity-driven linked systems.
Marine and Petroleum Geology, 75:151-180.
Shanmugam G. 2016. Slides, Slumps, Debris Flows, Turbidity Currents and Bottom Currents In:
Reference Module in Earth Systems and Environmental Sciences, Elsevier, 87 p.
Stow D.A.W., Reading H.G., Collinson J.D. 1996. Deep seas In: Reading H.G. (ed.). Sedimentary Environments: Processes, Facies and Stratigraphy. Oxford, Blackwell Science Ltd., p. 395-453.
Dados Acadêmicos
Mestrado; Data de ingresso na Pós-Graduação: 02/04/2018; Área de concentração: Geologia Exploratória; Linha de Pesquisa: Geologia estrutural de bacias sedimentares; Título original do projeto de pesquisa: Caracterização estrutural tridimensional do Depósito de Transporte em Massa Maricá, Bacia de Santos. Possui bolsa: Não
X X I S e m i n á r i o d o P r o g r a m a d e P ó s - G r a d u a ç ã o e m G e o l o g i a U n i v e r s i d a d e F e d e r a l d o P a r a n á
2 5 a 2 9 d e j u n h o d e 2 0 1 8 C u r i t i b a -‐ P R