Wave-dominated lacustrine margin of Aptian pre-salt: Mucuri Member, Espírito Santo Basin

https://doi.org/10.1016/j.jsames.2019.102490Get rights and content

Highlights

  • 19l facies are identified in the Mucuri Member.

  • Mucuri Member is compoused by gravelly fluvial channels and poorly confined fluvial channels deposits interlayered with shoreface to offshore lacustrine deposits.

  • 87Sr/86Sr indicated limited interaction with continental crustal materials, but still substantially higher than those of Cretaceous seawater.

  • Depositional model reconstruction need take into account the high-energy coastal processes.

Abstract

The Espírito Santo Basin, one of the Brazilian marginal basins formed during the Gondwana break-up, is composed by three main depositional units – rift, sag and drift phases. The Mucuri Member sandstones are the Aptian sag phase related, onshore reservoirs deposited at the margins of the lacustrine system were the pre-salt (pre-evaporitic succession) lacustrine carbonate reservoirs were generated. The main objective of this article focuses on the stratigraphic and sedimentological definition of depositional model from the top of the Mucuri Member, in the transition to Itaúnas Member evaporites of Mariricu Formation, since the depositional conditions of this interval until date remain under discussions and can contribute to the understanding of the correlated pre-salt reservoirs. Core description in detailed scale (1:50) associated with gamma-ray logs allowed the identification of nineteen facies, grouped into five facies associations: gravelly fluvial channel, poorly confined fluvial channels, upper shoreface, lower shoreface and offshore. Stacking patterns of facies associations allowed the definition of four cycles: T, T-R, normal R and forced R cycles. Although these cycles are easily recognizable in the cores, their correlation between wells was not possible. Geochemical analyses of 87Sr/86Sr ratio from anhydrites layers interbedded with the Mucuri sandstones confirmed a non-marine composition for the precipitating fluids. The integrated evidence suggests a wave dominated lacustrine coastal environment for the subaqueous Mucuri Member deposits.

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:

  • 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;

  • 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.

References (59)

  • D.L. Thompson et al.

    Lacustrine carbonate reservoirs from early cretaceous rift lakes of western Gondwana: pre-salt coquinas of Brazil and west Africa

    Gondwana Res.

    (2015)
  • R.B. Ainsworth et al.

    Wave-dominated nearshore sedimentation and 'forced' regression: post-abandonment facies, Great Limestone Cyclothem, Stainmore, UK

    J. Geol. Soc.

    (1994)
  • J.R.L. Allen

    The classification of cross-stratified units, with notes on their origin

    Sedimentology

    (1963)
  • J.R.L. Allen

    Studies in fluviatile sedimentation: bars, bar-complexes and sandsone-sheets (low-sinuosity braided streams) in the brownstones (L. Devonian), Welsh borders

    Sediment. Geol.

    (1993)
  • T.C. Blair et al.

    Alluvial fan processes and forms

  • W.H. Burke et al.

    Variation of seawater 87Sr/86Sr throughout Phanerozoic time

    Geology

    (1982)
  • A.S.G. Carvalho et al.

    The impact of early diagenesis on the reservoir quality of pre‐salt (Aptian) sandstones in the Espirito Santo basin, Eastern Brazil

    J. Pet. Geol.

    (2014)
  • T. Chakraborty et al.

    Evidence of lacustrine sedimentation in the upper Permian Bijori formation, Satpura Gondwana basin: palaeogeographic and tectonic implications

    J. Earth Syst. Sci.

    (2005)
  • H.E. Clifton

    A reexamination of facies models for clastic shorelines

  • H.E. Clifton

    Wave-formed sedimentary structures A conceptual model

  • J.D. Collinson

    Alluvial sediments

  • M. Dalrymple

    Interpreting sedimentary successions: facies, facies analysis and facies models

  • G. Dam et al.

    Cyclic sedimentation in a large wave and storm dominated anoxic lake: Kap Stewart formation (Rhaetian-Sinemurian), Jameson land, east Greenland

    Sedimentol. Assoc.

    (1993)
  • R.E. Denison et al.

    Isotopic data (Sr, S and O) from anhydrites in the northern Williston basin, and pennsylvanian ages for the Watrous and Amaranth formations of Saskatchewan and Manitoba

    Summ. Invest.

    (2001)
  • J.L. Dias

    Análise sedimentológica e estratigráfica do andar Aptiano em parte da Margem Leste do Brasil e no Platô das Malvinas: considerações sobre as primeiras incursões e ingressões marinhas do Oceano Atlântico Sul Meridional. 208 p. Tese de doutorado. Porto Alegre

    (1998)
  • S. Dorobek et al.

    Evidence for seasonal, abiotic precipitation and accumulation of carbonate sediments in the Pre-salt “Sag” successions of offshore Brazil

    AAPG Bull.

    (2012)
  • S. Dumas et al.

    Origin of hummocky and swaley cross-stratification— the controlling influence of unidirectional current strength and aggradation rate

    Geology

    (2006)
  • C.R. Fielding et al.

    Cyclicity in the nearshore marine to coastal, Lower Permian, Pebbley Beach Formation, southern Sydney Basin, Australia: a record of relative sea-level fluctuations at the close of the Late Palaeozoic Gondwanan ice age

    Sedimentology

    (2006)
  • R.L. França et al.

    Bacia do Espírito Santo

    Bol. Geociencias Petrobras

    (2007)
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