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Home , Campos Basin, Santos Basin, Sequence stratigraphy

Received: 27 December 2018 | Revised: 1 August 2019 | Accepted: 4 August 2019 DOI: 10.1111/bre.12397

EAGE SPECIAL ISSUE ARTICLE

What feeds shelf‐edge clinoforms over margins deprived of adjacent land sources? An example from southeastern

Uri Schattner1 | Francisco José Lobo2 | Adrián López‐Quirós2 | Jorge Luiz dos Passos Nascimento3 | Michel Michaelovitch de Mahiques3,4

1Dr. Mosses Strauss Department of Marine Geosciences, Charney School of Marine Abstract Sciences, University of Haifa, Haifa, Israel In southeastern Brazil, the coastal mountain range blocks the 2Instituto Andaluz de Ciencias de la Tierra, influx from arriving at a ca. 1,500 km long comprising Santos CSIC‐Universidad de Granada, Armilla, and Pelotas basins. Despite this deprivation, the margin accumulated a ca. 1 km thick Spain 3 sedimentary succession since the Mid‐. Examination of seismic reflection Oceanographic Institute, University of São Paulo, São Paulo, Brazil and oceanographic data indicates that shelf‐margin clinoform formation exhibits a 4Institute of Energy and regional variability, with major sigmoidal clinoforms developed in the transitional Environment, University of São Paulo, São area between both basins. Laterally, poorly developed oblique clinoforms constitute Paulo, Brazil isolated depocenters along the shelf margin. The continuous clinoform development Correspondence in the transitional area is attributed to the major influence on sediment transport pat- Uri Schattner, Dr. Mosses Strauss terns of several bottom currents flowing along the margin, such as the Brazil Department of Marine Geosciences, Charney School of Marine Sciences, Coastal Current, the Brazil Current and the Intermediate Water Brazil Current. These University of Haifa, Haifa, Israel. currents erode, transport and distribute across the shelf break and upper Email: [email protected] slope from distant sediment sources located either north or south of the study area.

Funding information The progressive southward strengthening of the Brazil Current could be responsible Fundação de Amparo à Pesquisa do for a major southward sediment redistribution from the northern , and/ Estado de São Paulo, Grant/Award Number: 2014/08266‐2, 2015/17763‐2 or for sediment entrainment from northward‐induced transport by the Brazil Coastal and 2016/22194‐0; CNPq, Grant/Award Current, originally derived from the De la Plata Estuary. In the transition between Number: 401041 and 2014‐0; Universidade Santos and Pelotas basins, the Intermediate Water Brazil Current splits forming the de São Paulo Santos Bifurcation, allowing for a continuous depositional process and clinoform generation. We suggest that ocean bottom currents may shape other shelf‐edge ‘con- touritic clinoforms’ in continental margins mainly constructed by along‐strike sedi- ment transport largely driven by long‐term geostrophic currents.

1 | INTRODUCTION 2007). In particular, the seaward development of modern continental margins is usually controlled by a hybrid type of Generations of clinoforms drive the outbuilding and develop- clinoform, with intermediate characteristics between shelf‐ ment of continental margins at different temporal and spatial edge (or shelf‐margin) and continental margin clinoforms scales (Patruno, Hampson, & Jackson, 2015), in response (Patruno & Helland‐Hansen, 2018), driven by the prograda- to the interaction between tectonic movements, glacio‐eus- tion towards the shelf edge of shelf clinoforms (Patruno et tatic sea‐level changes and sediment fluxes (Mountain et al., al., 2015).

© 2019 The Authors. Basin Research © 2019 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

wileyonlinelibrary.com/journal/bre | 293  Basin Research. 2020;32:293–301. 294 SCHATTNER et al. | EAGE In such distal locations, variations of accommodation space controlled by the balance between tectonic movements Highlights and eustatic sea levels are filled by regional conditions of sediment supply that will determine if the shelf edge will • Ocean bottom currents flowing along the SE prograde basinwards or will aggrade vertically to fill the Brazilian margin feed the shelf‐edge clinoforms. accommodation space. In the most general cases, sediment • The currents erode, transport, distribute sediments delivery to the shelf edge is presumed to be driven by flu- and dictate the depositional patterns. vial sources, causing shelf‐margin accretion and generation • Along‐strike ocean bottom currents, driven by of deep‐water clinoforms due to across‐shelf transits of long‐term geostrophic currents, may shape other shoreline/delta clinoforms (Patruno et al., 2015). As a con- shelf‐edge “contouritic clinoforms” worldwide. sequence, large‐scale shelf‐margin deltas incised by fluvial channels, with hundreds of meters high clinoforms and elon- gated regional extensions are preferentially formed (Patruno quiescence, in which large margin portions backstepped & Helland‐Hansen, 2018; Porębski & Steel, 2006) during (Contreras, Zühlke, Bowman, & Bechstädt, 2010). However, temporal scales up to 20 Ma (Patruno & Helland‐Hansen, most of its Cenozoic growth story has been determined by 2018). The major development of shelf‐margin deltas is con- a suppression of the fluvial supply by the blocking effect trolled either by great fluvially derived sediment fluxes and/ of coastal mountains (Cobbold, Meisling, & Mount, 2001; or periods of sea‐level fall during the (Porębski Mantovanelli, Tassinari, Mahiques, Jovane, & Bongiolo, & Steel, 2003). The Gulf of Mexico can be considered as 2018), and by the widespread effect of powerful oceanic cur- the most representative location where margin development rents (Biló, Silveira, Rocha, & Ceccopieri, 2014). Therefore, is mainly driven by successive generations of shelf‐margin it appears as an ideal location to study the potential effect deltas (e.g., Morton & Suter, 1996; Suter & Berryhill, 1985). of bottom current patterns on distal clinoform generation. However, there are certain settings where fluvial fluxes As thus, the main goals of the study are: (a) to determine are limited and/or prevented, and in such cases shelf‐margin the major sediment transport paths and bottom flow inter- sedimentation processes can be controlled by different types actions driving shelf‐margin clinoform formation; and (b) to of processes. For example, in continental margins which are propose a conceptual model for clinoform formation in mar- depleted of sources from the adjacent landmasses, fluvial gins whose major sediment sources are distant, since they are supply drastically decreases or even ceases over millions largely devoid of significant nearby fluvial supplies. of years. However, despite the starvation from the adjacent landmass, ocean bottom currents may continue to supply sediments over hundreds of kilometers until deposited across 2 | REGIONAL SETTING distant parts of the , off the main source‐to‐ sink axis (Schattner & Lazar, 2016). In fact, long‐lasting bot- 2.1 | Geological setting tom‐current flows are able to generate a suite of sedimentary The study focuses on the Mid‐Miocene to recent sedi- products that can be categorized as shallow‐water contou- mentary succession of the southeastern Brazilian con- rites deposits. These shallow can be composed tinental margin (Figure 1), extending between latitudes by a variety of depositional and erosional elements than in 24.5°S–35°S. This ca. 1,500 km long section includes the general terms exhibit a more patchy distribution than their continental margins of the Santos and Pelotas basins. The deep‐water counterparts, and which are the response to more major tectonic lineament known as the Florianópolis High varied and less steady oceanographic processes (Verdicchio divides between the two basins at the subsurface of the & Trincardi, 2008). Indeed, some studies indicate that a continental margin (Rosa, Barboza, Abreu, Tomazelli, & fraction of shelf‐margin clinoform materials may arrive Dillenburg, 2017), while Rio Grande Terrace distinguishes via along‐shore transport (e.g., Friedrichs & Scully, 2007; between their morphological expression at the ocean floor Mosher et al., 2017; Schattner & Lazar, 2016; Wright et al., (Zembruscki, Barreto, Palma, & Milliman, 1972). Santos 1988). In some extreme cases, significant episodes of margin and Pelotas basins record the entire evolution from in may be driven by powerful submarine currents, the to in the (Modica suggesting that local processes may exert a considerable in- & Brush, 2004). The contains a ca. 10 km fluence on sequence architecture, obliterating to a large ex- thick sedimentary succession that is characterized by ex- tent the glacio‐eustatic signal (Lu & Fulthorpe, 2004). tensive halokinetic structures rooted in late to early We focus here on the southeastern Brazilian margin and carbonates (Schattner et al., 2018 that receives negligible supply from the adjacent land. The and references therein). These structures were buried by a growth of this margin has been driven by alternations of thick progradational wedge that shifted to in major progradational periods with intervals of sedimentary the Tertiary (Contreras et al., 2010). The Pelotas Basin did SCHATTNER et al. 295 EAGE |

FIGURE 1 Location map crossing the central part of (inset), showing the Paraná River drainage (green, flow direction – red arrows) bounded by the Andes and Serra do Mar (SDM) ranges from west and east (respectively, brown). Thin black lines mark the location of seismic profiles across the Santos margin (SM), Florianópolis High (FH) and Pelotas Margin (PM) of the southeastern Brazilian margin. Main oceanographic currents are Brazil Coastal Current (BCC, green), Brazil Current (BC, red) and Intermediate Water Brazil Current (IWBC, blue). SBf – Santos Bifurcation, RdlP – Río de La Plata, BA – Buenos Aires, M – Montevideo, PA – Porto Alegre, SP – São Paulo, R – . Light blue circles mark the location of wells used for stratigraphic correlation (after Contreras et al. 2010) not accumulate evaporites. Their ‐Paleogene depths. The Brazil Current (BC in Figure 1) flows southeast- succession includes pelagic deposits arranged in a retrogra- ward along the shelf margin and upper slope in the uppermost dational pattern. However, the stacking pattern changed to 500 m of the , with a maximum in its core of progradational during the Neogene (Contreras et al., 2010). about 0.59 m/s that decrease with depth to zero at ca. 500 m The different stacking patterns in Santos and Pelotas (Biló et al., 2014). This current carries the Tropical Water basins are directly related to the evolution of two mountain mass at surface levels and the South Atlantic Central Water ranges, which played a key role in controlling the regional mass (TW and SACW in Figures 2‒4) at pycnocline levels. sediment fluxes towards the study area. In Santos Basin, the The Brazil Current is crucial in determining the sedimentary supply of clastic sediments decreased in the early (ca. balance of the outer shelf, shelf‐edge and upper slope of the 55 Ma) and was inhibited during the Neogene, due to the up- Brazilian margin. The kinetic energy of quasi‐perma- lift of the Serra do Mar coastal mountain range. This crys- nent meanders and vortices of the Brazil Current intensifies talline (, migmatites and ) mountain range southwards (e.g., Assireu, Dauhut, Santos, & Lorenzzetti, maintained its average 1,200 m altitude above due 2017). Further south, the Brazilian Coastal Current (BCC in to the interplay between denudation and non‐orogenic uplift Figure 1) flows most of the year along the inner Uruguay and (Salgado et al., 2014). The western flank of Serra do Mar Pelotas shelves to the northeast, paralleling the Brazil Current diverted fluvial supplies either to Campos Basin in the north but in the opposite direction, up to the centre of the Santos (Cobbold et al., 2001) or to the Paraná River basin in the shelf (Mendoça et al., 2017; de Souza & Robinson, 2004). west (Cogné, Gallagher, Cobbold, Riccomini, & Gautheron, At intermediate water depths of 500–1,800 m, the conti- 2012; Riccomini, Sant’Anna, & Ferrari, 2004). Denudation nental slope faces the western portion of the Subtropical Gyre products of its ocean‐facing eastern flank were not reported (Stramma & England, 1999). The Gyre currents approach to have a contribution to the build‐up of the continental the Florianópolis High slope at around 27–28°S, where it shelf (de Mahiques et al., 2008). In Pelotas Basin, the higher splits into two branches to form the Santos Bifurcation (SBf post‐Miocene accumulations were possibly derived from the in Figure 1). The northern branch flows northeastwards contributions of the Paraná River (Milliman, 1978) and/or along the lower Santos continental slope as the Intermediate favoured by the uplift of source areas caused by the Andean Western (IWBC in Figure 1). The core of (Contreras et al., 2010). The present‐day situation is the IWBC flows at about 800 m water depth with velocities of characterized by the dominance of the Paraná River sediment 0.2–0.3 m/s (Biló et al., 2014; da Silveira et al., 2004) mainly supply, whose drainage areas supply most of the modern ter- transporting Antarctic Intermediate Water (AAIW in Figures rigenous sediments to the Pelotas and Santos basins, up to ca. 2‒4). The velocity decreases to zero at 1,800 m water depths 25°S (de Mahiques et al., 2008). (Biló et al., 2014; de Mahiques et al., 2011; Piola, Campos, Möller, Charo, & Martinez, 2000; de Souza et al., 2004) within the interface between Antarctic and North Atlantic 2.2 | Oceanographic setting Deep Water masses. The southern branch of the bifurcation Three main oceanic current systems flow along the south- flows southwestwards along the Pelotas Basin slope (e.g., eastern Brazilian margin at shallow, intermediate and deep Schmid, Siedler, & Zenk, 2000). At water depths greater 296 SCHATTNER et al. | EAGE

FIGURE 3 Time migrated multichannel seismic reflection profile crossing the Florianópolis High (Rio Grande Terrace), showing the entire sedimentary succession comprising the continental margin (a), and a closeup to the Mid‐Miocene to recent succession (b). Markings and abbreviations are similar to Figure 2. Location in Figure 1 FIGURE 2 (a) Time migrated multichannel seismic reflection profile crossing the Santos Margin. Note the alterations in depositional patterns across the outer shelf (b). Yellow arrows – downlap, blue in the studied interval. Identification of seismic reflectors and arrows – toplap, green arrows – clinoform progradation/, subsequent correlation with boreholes and stratigraphic data white circle – current flowing towards the reader, white circle with is based on previous interpretations by Modica and Brush a cross ‐ current flowing away from the reader. Selected erosional (2004), Contreras et al. (2010), and de Mahiques et al. (2017). are marked with white lines (black shade). White The correlation between well and seismic reflection data arrows mark truncation surfaces. BSR – Bottom Simulating Reflector, served as a basis for correlating across the Santos basin (see TW – Tropical Water, SACW – South Atlantic Central Water, AAIW Figures 3 and 6, respectively, in Contreras et al., 2010) and – Antarctic Intermediate Water, TWT – Two Way Travel‐time, Pelotas basin (see Figure 4 and 6, respectively, in Contreras BC – Brazil Current, IWBC – Intermediate Water Brazil Current. Rainbow colours above the ocean floor represent the temperature et al., 2010). Loop‐tie interpretation of reflectors, and in par- gradient. Location in Figure 1 ticular the Mid Miocene , was extended across the entire dataset including areas where well data are lacking interpretation. Selected profiles are presented in Figures 2‒5, along with hydrographic cross‐sections of temperature (°C) than 2,000 m, the Deep Western Boundary Current (DWBC) (Figures 2‒4) constructed using the Ocean Data View™ soft- transports the North Atlantic Deep‐Water southwards along ware (Schlitzer, 2018). Hydrographic data, extracted from the margin (Stramma & England, 1999). the World Ocean Database 2013 (WOD13; see website https​ ://www.nodc.noaa.gov), allowed a joint analysis of the inter- play between the and clinoform generation. 3 | DATA This study is based on the interpretation of 2D time‐migrated 4 | RESULTS multi‐channel seismic reflection profiles summing 19,100 km in length (Figure 1). The data were acquired over an area of The Mid‐Miocene Unconformity is mappable across the en- 562,000 km2 during six surveys since 2000 that were released tire study area, despite the appearance of a prominent Bottom for academic use by the National Agency for Oil, Natural Simulating Reflector (BSR in Figures 2‒4). The stacking pat- Gas and Biofuels (ANP‐Brazil). These positive polarity seis- tern of seismic units above the unconformity is aggradational mic profiles extend down to 7, 8, 9, 10 and 12 s two‐way to slightly retrogradational along much of the study area, al- travel‐time (TWT) with a sample rate of 4–8 ms, a fold of though in the Pelotas Basin progradational stacking patterns 50–109, and vertical resolution of a few meters per reflector are observed. SCHATTNER et al. 297 EAGE |

FIGURE 4 Time migrated multichannel seismic reflection profile crossing the Pelotas Margin. Markings and abbreviations are similar to Figure 2. Note the lack of a clear clinoform. Location in Figure 1

Along the study area, different types of clinoform de- velopment were identified during the studied interval (i.e. after the Mid Miocene). In Santos Basin, clinoform patterns have changed significantly through time. The lower part of the succession exhibits a package of well‐developed sig- moid clinoforms, substituted upward by two major phases of moderate shelf‐margin progradation through low‐angle oblique‐parallel shelf clinoforms that tend to become steeper towards the shelf margin. These recent phases exhibit ero- sional truncations over the outer shelf, as well as a number of FIGURE 5 (a) Map of sea surface temperatures from May distal truncations in the upper slope, that tend to be onlapped 26, 2018, across the Florianópolis High (FH) and Pelotas Margin by rather chaotic lenses. The most recent sub‐surface stra- (PM). Map from State of the website of NASA (https​:// podaac.jpl.nasa.gov/). The transition between the NE‐flowing Brazil tigraphy contains parallel‐oblique clinoforms on the upper Coastal Current (BCC, green arrow) of the inner shelf, and the SW‐ slope under the influence of the SACW that become gen- flowing Brazil Current (BC, red) is marked on both the map (a) and tler downslope, at the boundary between SACW and AAIW the time migrated multichannel seismic reflection profile crossing (Figure 2). the Pelotas Margin (b). Markings and abbreviations are similar Well‐developed sigmoidal clinoforms overlying an ero- to Figure 2. Location in Figure 1 sional unconformity are identified in the transitional zone be- tween Santos and Pelotas basins, in the Rio Grande Terrace (Figure 3). There, the distal part of the clinoforms extends down to isobaths of ca. 1,500 m. While the orientation of elongated, coast‐parallel, bulge (Figure 5a). This bulge follows the 2D seismic reflection profiles limits the imaging of the the trace of the Brazilian Coastal Current up to the Florianópolis subsurface to the direction of the seismic pro- High. Over a sharp, coast‐parallel, transition, this morphology files, it seems that in this specific area clinoforms prograde shifts to a flat and erosive outer shelf (Figure 5b). There, the in multiple directions, ranging from NE to WSW. The outer shelf‐margin development led by clinoforms is much more mod- shelf is marked by a rough surface with some evidence of ero- erate, with the prevalence of poorly developed parallel‐oblique sional truncations, under the direct influence of the SACW. clinoforms affected at the top by erosional truncations that are The low‐lying distal parts of the clinoforms also seem to be developed below the flow path of the BC. truncated on the slope (Figure 3). Further southward, clinoforms are very poorly developed Immediately south from the Rio Grande Terrace, well‐de- to none existent in Pelotas Basin. There, the shelf‐margin and veloped sigmoid clinoforms are no longer observed (Figure 5). upper slope exhibit frequent chaotic with some alter- Instead, two well‐defined shelf domains are distinguished on the nations of stratified facies. However, the long‐term stacking basis of seismic facies and morphology. The post‐Mid‐ pattern seems to be more progradational than in the northern Miocene succession thickens over the inner shelf to form an areas. The boundary between the SACW and the AAIW is 298 SCHATTNER et al. | EAGE scheme does not seem to apply to the southeastern Brazilian shelf‐edge clinoforms, that accumulated up to ca. 1 km of sedi- ments since the Mid‐Miocene. In the study area, most of the sediments did not arrive directly from the adjacent landmass since the Serra do Mar coastal range has diverted the supply southwards to the Paraná watershed and northeastwards to the Campos Basin (Cobbold et al., 2001; Cogné et al., 2012). These sediment supply conditions that imply the existence of a remote source from these locations. We propose that ocean bottom cur- rents transported part of this supply along the continental margin until accumulating over the shelf‐edge clinoforms (Figure 6). One possibility could be related with the entrainment of sediments provided by Parnaíba do Sul River into Campos Basin, and preferential southward sediment transport along the outer shelf by the BC, which in general terms exhibits a progressive southward increase in intensity (Biló et al., 2014). The sedimentary consequences of such transport are imprinted in the shelf‐margin record, where the formation of significant clinoform patterns is enhanced towards the south (Viana & Faugères, 1998; Viana, Hercos, Almeida, Magalhães, & Andrade, 2002). In Campos Basin, an off‐shelf sediment transport of sandy sediments has been detected. Those sed- iments tend to be reworked by the southward‐flowing BC, generating a suite of erosional morphologies and bedforms of FIGURE 6 Isopach of the Mid‐Miocene to recent succession contouritic nature. Part of these sediments would feed a poorly over the study area. Red arrows emphasize the fluvial flow away developed clinoform in Santos Basin; the reported increase from the continental margin towards the Paraná River drainage. in the intensity of the BC towards the south would cause the SDM – Serra do Mar, SP – São Paulo, SM – Santos margin, FH – Florianópolis High, PM – Pelotas Margin. Thickness values in of outer shelf clinoforms and would provide enough the time domain (msec Two Way Travel‐time) appear along with sediments for the construction of a thick clinoform in the tran- the abundance histogram. Orange arrows schematically mark the sitional area between Santos and Pelotas basins. directions of clinoforms across the FH. Another viable sediment source could be derived from De la Plata Estuary, since the BCC could entrain a portion of the sediment fluxes northward along the inner shelf; in fact, apparently not connected with a recognizable facies or geo- a number of shelf depocenters have been identified along morphological boundary (Figure 4). the path of the BCC (Milliman, 1978). It is conceivable that The isopach of the Mid‐Miocene to recent succession part of this sediment transport could arrive at the area of shows significant thickness variations across the study area BC dominance, in the transitional area between Santos and (Figure 6). Over most of the inner shelf and lower slope, Pelotas Basin. In this last basin, the uplifting of source areas thickness ranges between 100–300 ms. Thickness varia- driven by the Andean orogeny led to an intensely prograda- tion range increases to 300–1,400 ms across the outer shelf, tional pattern during the Neogene (Contreras et al., 2010) shelf‐edge and upper slope. The shelf‐margin depocenters are and to the dominance of gravitational processes, with poor patchy and discontinuous across the margin. A major NE‐ development of shelf‐margin clinoforms. SW shelf‐margin depocenter occurs in Santos Basin. Several The favourable sediment transport conditions (either shelf‐margin depocenters also occur around the Florianópolis from the north or from the south) were enhanced over the High, in coincidence with the occurrence of the major sig- Florianópolis High, where the sediment surplus derived from moidal clinoform. Finally, several small, isolated depocenters the BC allowed the continuous formation of a shelf‐edge sig- are identified in the Pelotas Basin (Figure 6). moidal clinoform. The effect of a meandering BC coupled with the Coriolis effect may have enhanced the off‐shelf sed- iment transport and fallout at shallow water depths < 500 m. 5 | DISCUSSION This long‐term process is attested by two major margin pro- tuberances (Including the Rio Grande Terrace) found in the The formation of shelf‐edge clinoforms is frequently associated transitional area between the two major basins (Figure 6). with a fluvial‐fed system (Porębski & Steel, 2003). That general The development of the sigmoidal clinoform is also related SCHATTNER et al. 299 EAGE | to the spatial relationship between the BC and the IWBC. margin represent a combination of (1) erosion and transport Hence, in this area the Santos Bifurcation shelters the fallout by ocean bottom currents, and (2) deposition and preserva- from being transported away by the IWBC, since the flow tion over preferred areas with low flow velocities. strength and transport capacity decreases over this current By one hand, the BC, flowing southwest, entrains and splitting. This combination allows the Rio Grande Terrace to transports sediments coming from remote sources and develop basinward through a continuous build‐up of prograd- erodes the outer continental shelf down to ca. 500 m water ing clinoforms that reach deeper isobaths compared to the depth in response to a progressive southward strengthen- Santos and Pelotas basins. ing. On the other hand, surplus sediments that are deposited Given the limited sediment influx from the adjacent from the BC are transported to the shelf‐edge and down the land, the variability in shelf‐margin clinoform patterns and slope to construct a major sigmoidal clinoform in the tran- the depositional styles across the southeastern Brazilian sitional area between Santos and Pelotas basins, where the margin can be attributed almost entirely to variations of IWBC splits into two branches (i.e. Santos Bifurcation). ocean currents in magnitude and direction. In agreement Away from the transitional area, clinoform formation is not with the observation of other margins swept by power- favoured since the surplus sediments are transported later- ful ocean currents, such as the Canterbury margin, thick ally by the IWBC. shelf‐margin clinoforms can be interpreted as a type of While the connection between ocean bottom flows and shallow‐water ‘contouritic clinoforms’ (Lu & Fulthorpe, formation is well‐established, our paper provides 2004). These particular contourites differ from the typical a clear case study for the dominance of along‐margin ocean shallow‐water contourites, normally represented by thin bottom flow on the formation of shallow‐water ‘contouritic sand sheets molded by bedforms and/or erosive features clinoforms’. This case study highlights the importance of (Verdiccio & Trincardi, 2008), signalling the dominance ocean bottom currents in the construction of shelf‐margin of reworking and/or erosive processes. In contrast, the oc- clinoforms in areas located far from significant fluvial sed- currence of contourite clinoforms would indicate the prev- iment sources. alence of geostrophic currents driving regional transport patterns during long time spans. Therefore, it is proposed ACKNOWLEDGEMENTS that under certain conditions, ocean bottom currents may control the stratigraphic development of continental mar- The authors are indebted to the Brazilian Navy, who pro- gins. In this kind of settings, along‐strike sediment trans- vided the echo‐sounding data and to the Brazilian National port driven by powerful shelf‐margin currents may be Oil Agency (ANP), for providing the seismic lines. considered as the primary factor driving the generation of Financial support was provided by the São Paulo Science shelf‐margin clinoforms and subsequent sequence develop- Foundation (FAPESP, grants 2014/08266‐2, 2015/17763‐2, ment (Lu & Fulthorpe, 2004). Inversely, we suggest that and 2016/22194‐0). F.J. Lobo acknowledges the Brazilian the stratigraphic pattern of certain shelf‐edge clinoforms program “Ciência sem Fronteiras” funded by the can also be used for reconstructing the ocean bottom con- CNPq, enabling him to conduct several research stages ditions which contributed to their formation. as “Pesquisador Visitante Especial” at the Instituto Oceanográfico, Universidade de São Paulo, under project number 401041/2014‐0. We thank Petrel‐Schlumberger for 6 | CONCLUSIONS providing academic licenses that enabled the seismic inter- pretation. We thank the editors Claudio Pellegrini, Stefano Over the ca. 1,500 km long continental margin of southeast- Patruno, Ron Steel and William Helland‐Hansen, an anon- ern Brazil the sediment supply from the adjacent terrestrial ymous reviewer as well as Craig Fulthorpe and Tore Grane sources is negligible, whereas most of the sediments are car- Klausen for their constructing review. The authors declare ried and eroded by oceanic currents that follow the strike of to have no conflict of interest. the continental margin. Seismic reflection data along Santos and Pelotas basins show that, since the mid‐Miocene, a major DATA AVAILABILITY STATEMENT sigmoidal clinoform pattern formed preferentially across the Rio Grande Terrace shelf edge. Sporadic evidence for The data that support the findings of this study belong to the clinoforms was found along Santos and Pelotas basins, yet a Brazilian National Oil Agency (ANP) and was provided to well‐defined sigmoidal pattern is lacking. Correlation of the this research following the approval of a formal request. interpreted sedimentation pattern and the preferred location of the clinoforms with the main current flow pathways, sug- ORCID gests that the on‐going sedimentation, the stratigraphic clin- oform patterns and their patchy distribution along the shelf Uri Schattner https://orcid.org/0000-0002-4453-4552 300 SCHATTNER et al. | EAGE REFERENCES Margin. Frontiers in Science, 6, 74. https://doi.org/10.3389/​ feart.2018.00074​ Assireu, A. T., Dauhut, T., dos Santos, F. A., & Lorenzzetti, J. A. Mendonça, L., Souza, R., Aseff, C., Pezzi, L., Möller, O., & Alves, R. (2017). Near‐inertial motions in the Brazil current at 24° S‐36° (2017). Regional modeling of the water masses and circulation an- S: Observations by satellite tracked drifters. Continental Shelf nual variability at the Southern Brazilian Continental Shelf. 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