Wave-dominated lacustrine margin of Aptian pre-salt: Mucuri Member, Espírito Santo Basin
Introduction
The sedimentation in lakes is considered to be predominantly dominated by low-energy depositional processes, with some influence of fluvial systems along the margin. However, sedimentological studies of actual lakes (Nutz et al., 2016) have demonstrated that wave-dominated clastic shorelines can represent a significant portion of coastal zone of lakes, standing out the Turkana Lake (Kenya), Azov Sea (Ukrainia/Russia), Megalake Chad (Chad) and Lake Qinghai (China). Paleolacustrine examples in which facies associations indicate lacustrine shoreface dominated by normal and storm waves are rare too (Chakraborty and Sarkar, 2005; Ilgar and Nemec, 2005). The wave-dominated clastic shorelines can represent a significant portion of coastal zone of lakes (Nutz et al., 2016) and is necessary to take it into account in the regional paleoenvironmental and paleogeographic reconstruction of the basin.
The proximal context of sedimentary basins reflects a set of interdependent depositional processes, involving the transfer of sediments by fluvial systems from the source area to coastal regions and the distribution of these sediments by coastal processes to the inner portions of the basin (Reading, 1996). Therefore, the depositional dynamics of the coastal regions may directly impact the distribution pattern and the type of sediments that occur in the distal portion of the basin. The Mucuri Member record the deposition in the proximal portions of the Espírito Santo Basin at the same time interval in which pre-salt (pre-evaporitic sucession) lacustrine deposition became deposited in distal portions of the basin. Understanding the depositional dynamics of the Mucuri Member, fringing or bordering lacustrine system, is essential to fully comprehend the deposition inside the lake, besides providing a depositional model of a high-energy lacustrine margin.
The main objective of this paper focuses on the stratigraphic and sedimentological definition of the top of Aptian pre-salt Mucuri Member (Espírito Santo Basin) and the configuration of depositional dynamics wave-dominated lake system. As specific objectives, the following can be highlighted: (i) to define the lithofacies, facies associations and depositional model of the proximal deposits of the pre-salt sag basin, (ii) to characterize the anatomy of high-frequency transgressive-regressive cycles, (iii) to define the marine or lacustrine affinity of the top section of the pre-salt deposits.
Section snippets
Geological setting
The Espírito Santo Basin (Fig. 1) which covers more than 41,500 km2 was formed by rifting process which break-up Gondwana and originated the South Atlantic Ocean (França et al., 2007). It is separated from the Mucuri basin to the north by the volcanic Abrolhos Plateau and at south is limited with Campos Basin by the Vitória High (França et al., 2007). The basin is subdivided in two platforms and two Paleocene canyons: São Mateus Platform bounded by Fazenda Cedro Paleocanyon to the north;
Methods
The sedimentological data were collected through detailed description and interpretation of the stratigraphic sections logged in 13 cored wells (Fig. 3), totalizing 430 m of cores described in 1:50 high-resolution scale. The facies were classified based on grain-size and sedimentary structures, following the schemes of Miall (1977). The facies were grouped into facies associations, representing a sub-environments within a depositional system (Collinson, 1996; Dalrymple, 2010). Finally, the
Lithofacies
Sixteen depositional facies and three post-depositional facies are recognized in the Mucuri Member (Table 2, Fig. 4). The Mucuri Member is composed mainly of sandstones and subordinately by conglomerates, mudstones and anhydrite. The sandstones are very fine-to coarse-grained (mostly medium-grained), stratified or massive, moderately-sorted, with subangular to rounded grains. Fine-grained sandstones are micaceous. Quartz pebbles are common in coarse-grained sandstones. The conglomerates are
Depositional systems
The presence of gravelly fluvial channel and poorly confined fluvial channel facies associations laterally and vertically interlayered with upper shoreface, lower shoreface and offshore deposits indicates a transitional depositional environment between an alluvial plain and an adjacent lacustrine or marine basin. In many cases the distinction between marine and lacustrine environments is difficult due to the similarity of the active depositional processes, since facies generated by waves can
Conclusions
The following conclusions have been deduced from the integrated study of the upper portion of Mucuri Member:
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Sixteen depositional facies and three post-depositional facies are identified in the Mucuri Member and are composed mainly of arkosic sandstones and subordinately by conglomerates, mudstones and anhydrite;
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The genetically-related lithofacies defined six facies associations: (i) gravelly fluvial channel, (ii) poorly confined fluvial channels, (iii) upper shoreface, (iv) lower shoreface, (v)
CRediT authorship contribution statement
Camila Eliza Althaus: Data curation, Writing - original draft. Claiton Marlon dos Santos Scherer: Data curation, Writing - original draft, Writing - review & editing. Juliano Kuchle: Data curation, Project administration, Funding acquisition, Writing - review & editing. Adriano Domingos dos Reis: Data curation, Writing - review & editing. João Pedro Formolo Ferronatto: Data curation, Writing - review & editing. Luiz Fernando De Ros: Data curation, Writing - original draft, Writing - review &
Declaration of competing interest
We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.
Acknowledgements
This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), which provided the first author's Master's Degree scholarship. We thank to Carrel Kifumbi support with graphic model. The authors gratefully acknowledge support from Shell Brasil Petróleo Ltda and the strategic importance of the support given by ANP (Brazil's National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation.
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Lower Permian aeolian dunes surrounding lakes in Gondwana: Insights on depositional dynamics, cyclicity pattern and climatic control from the Parnaiba basin (Brazil)
2022, Journal of South American Earth SciencesCitation Excerpt :Therefore, a wave-dominated lacustrine depositional model bordered by coastal aeolian dune fields can be proposed for the middle interval. The facies succession composed by offshore transition to shoreface deposits is indicative of large lake bodies, which have an extensive water surface sufficient for the winds to generate waves that systematically move sediments on the bottom, generating expressive deposits of fairweather and storms (Chakraborty and Sarkar, 2005; Ilgar and Nemec, 2005; Keighley, 2008; Althaus et al., 2020). The higher proportion of aeolian deposits in outcrop 2 in relation to outcrop 1 (Fig. 15), as well as the thicker occurrence of offshore transition deposits in the base of outcrop 1, indicates a context more proximal to northwest (outcrop 2) and more distal to southeast (outcrop 1), suggesting that the depositional area of the basin extended much further southeast than its current erosive limits.
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2021, Sedimentary GeologyCitation Excerpt :Håkanson (1982) proposed a classification of the sedimentary dynamics of lakes that contain fluvial-dominated systems and wind wave-dominated systems. The wave-dominated shoreline system controlled by winds represents a significant portion of the coastal domain of lakes (e.g., Nutz et al., 2018; Jiang, 2018; Althaus et al., 2020). For example, many Holocene lakes, such as Megalake Chad in Sahara (Bouchette et al., 2010; Schuster et al., 2014), Turkana Lake in Kenya (Schuster and Nutz, 2018; Nutz et al., 2020) and Qinghai Lake in China (Zhang et al., 2016; Jiang et al., 2018; Wang et al., 2018a; Hao et al., 2019), exhibit wave-dominated shoreline landforms in the form of spits, wave-cut platforms, longshore bars, beaches, berms and washover fans (e.g., Magee and Miller, 1998; Renaut and Owen, 1991; Davidson-Arnott and Van Heyningen, 2003; Schwartz, 2012; Zhang et al., 2016; Schuster and Nutz, 2018).
Model for calcite spherulite formation in organic, clay-rich, lacustrine carbonate shales (Barbalha Formation, Aptian, Araripe Basin, NE Brazil)
2021, Marine and Petroleum GeologyCitation Excerpt :The Cretaceous is known worldwide for its short-term eustatic sea-level changes (Ray et al., 2019). Large-scale marine ingressions were occasional (Silva-Telles et al., 1994; Althaus et al., 2020; Rodrigues et al., 2020) and are recognized within these basins during the early Aptian (e.g. Crato Formation) but also for the overlying evaporites (Ipubi Formation in the Araripe Basin). The Barbalha laminites and spherulites are remarkably similar when comparing with Pre-Salt data and descriptions, not only to those reported on the Brazilian side of the South Atlantic but also in their West-African counterparts (examples of spherulites in e.g. Herlinger et al., 2017; Farias et al., 2019; Lima and De Ros, 2019 and Wright and Barnett, 2020).