As North America Rifted From Europe and Africa a Continuous Rift System Called the Was Formed
The southeast Brazilian rifted continental margin is not a single, continuous upwarp: Variations in morphology and denudation patterns along the continental drainage divide
Abstract
Rifted continental margins (RCM) are large-scale features of Earth's surface that show substantial morphological variations. Classical escarpment features are the subject of many studies in these settings while other morphologies that characterize this tectonic environment receive less attention. The case of the Brazilian South Atlantic margin, a continental-scale topographically pronounced terrain covering >1000 km of the western South Atlantic rifted margin, is not an exception. Most landscape evolution studies concentrate on the Serra do Mar escarpment system, while other segments with no escarpments have received less attention. Various authors assume the Brazilian elevated continental margin as a well-defined and continuous marginal upwarp instead of a diversified and more complex landscape. Here we debate this issue and explore how the first-order topographic forms and time-space denudation patterns differ along the Brazilian South Atlantic margin. We focus on the continental margin of southeast Brazil (CMSEB) that includes a southern segment featured by a prominent escarpment system and a northern segment where the seaward-facing steep escarpment is absent. We show that, similar to other RCMs, the CMSEB presents a continental drainage divide separating two distinct regions with contrasting denudation patterns, (i) an inland continental interior, characterized by high elevation and relatively low relief with a predominance of apatite fission track (AFT) ages significantly older than South Atlantic rifting event, and (ii) a coastal region characterized by low elevations and high relief with the predominance AFT ages younger than the rifting. However, besides the differential denudation associated with the South Atlantic opening, the margin has experienced substantial post-rift exhumation attributed to rock uplift triggered by the reactivation of inherited basement structures. The morphological differences between CMSEB's southern and northern extensions reflect sectors with contrasting geomorphic evolution supporting the idea that the rifted Brazilian RCM is not a single and continuous tectonic setting. Finally, our findings indicate that tectonic inheritance strongly impacts the denudation pattern, which contributes to the geomorphic diversification along the Brazilian RCM.
Introduction
The morphology of elevated rifted continental margins (RCM) is commonly defined by a steep sea-ward escarpment running parallel to the coast with >1 km of elevation, and separating an upland continental interior plateau with low relief from a medium to high relief coastal plain of varying width, with examples including southeastern Brazil, eastern Australia, southern Africa, and western India (Braun, 2018a). Such high and steep topography is more reasonably explained in the context of active rifts than in mature 'passive' margins, and thus many authors have attempted to resolve its enigmatic persistence (e.g., Ollier, 1982; Gilchrist and Summerfield, 1990; van der Beek et al., 1995; Persano et al., 2002; Braun and van der Beek, 2004; Japsen et al., 2012a, Japsen et al., 2012b; Green et al., 2013; Braun, 2018a, Braun, 2018b; Japsen et al., 2018). High relief in RCM has been attributed to the operation of thermo-mechanical processes in the lithosphere-asthenosphere interface capable of driving rock uplift long after the continental breakup, such as domal or dynamic uplift (e.g., Ruetenik et al., 2016), depth-dependent extension (e.g., Royden and Keen, 1980), secondary convection (e.g., Armitage et al., 2013; Sacek, 2017), lithospheric necking (e.g., Braun and Beaumont, 1989), denudational flexural-isostatic rebound (Gilchrist and Summerfield, 1990), and magmatic underplating (e.g., McKenzie, 1984). However, these factors are generally suggested as components of end-member scenarios that, nonetheless, do not fully address the intricate topographic evolution of one particular RCM or apply to all cases (Gallagher and Brown, 1997). To date, the evolution of rifted margins is generally agreed to involve a highly complex, multiphase process (Peron-Pinvidic et al., 2019).
Marginal upwarps on RCMs are significant large-scale features of Earth's surface. Their topographic configuration differs from high elevation domains flanked by wall-like escarpments (e.g., southern Africa, western India, and southeastern Australia) to low amplitude upwarps located at low elevations in settings such as eastern India, eastern Argentina, and southern Australia. However, even rifted margins characterized by the classic morphology of a sharp escarpment form, in reality, far more complex landscapes, where relief varies from one part to another along their length of thousands of kilometers. In this situation, it is reasonable to assume that differing landscape histories likely explain substantial morphological variations along the length of a RCM, similar to consensual interpretations in vast mountain systems such as the Andes (e.g., Schildgen and Hoke, 2018). Nonetheless, the majority of empirical and numerical studies in these settings concentrated on the formation and evolution of 'Great Escarpments', and generic conceptual models of margin evolution (e.g., 'downwarp', Ollier and Pain, 1997; 'scarp retreat', Gilchrist et al., 1994; 'pinned divide or downwearing', Kooi and Beaumont, 1994) were proposed to explain the long lifespan of such escarpments. In contrast, fewer studies explored links between lateral changes in relief and bedrock geology and the post-breakup evolution in RCM (e.g., Persano et al., 2006; Calegari et al., 2021; Codilean et al., 2021), even though some authors have highlighted that topography changes substantially along the extensive length of these settings (e.g., Gallagher et al., 1998; Persano et al., 2002; Bishop, 2007; Japsen et al., 2012a; Braun, 2018a).
In this contribution, we concentrate on investigating the landscape variability along the Brazilian elevated RCM by exploring quantitatively how first-order topographic forms and the pattern and chronology of the long-term denudation differs throughout the length of one such vast rifted setting extending for >3000 km along the western South Atlantic coast. In this situation, it is symbolic that numerous studies show the Brazilian elevated-RCM as a single, well-defined and continuous continental margin upwarp (e.g., Summerfield, 1991; Matmon et al., 2002). Nevertheless, some authors emphasized significant morphological changes along the Brazilian coast (e.g., Jelinek et al., 2014; Braun, 2018a; Calegari et al., 2021), although the precise ways through which topography and post-breakup denudation patterns differ spatially over the length of the Brazilian RCM remain to be evaluated. Here, we focus on the onshore segment related to Santos, Campos, and Espírito Santo offshore basins (Mohriak et al., 2008), which is referred to as the continental margin of southeast Brazil (CMSEB). We perform quantitative topographic analysis to define the marginal drainage divide and explore differences in topography between the inland and seaward-dipping sides of the divide along the Brazilian South Atlantic rifted margin. In addition, we take advantage of the large set of apatite fission track data available to explore variations in denudation patterns and the thermal evolution of the crust from the inland plateau to the continental water divide and up to the baselevel. We concentrate on differences in these inland-to-coast exhumation profiles over the margin's southern and northern extensions addressing interactions with potential controls such as the basement structural framework, lithological variability, and flexural strength of the lithosphere.
Section snippets
Geological setting
The study area is the continental margin of southeast Brazil (CMSEB), a continental-scale topographically pronounced terrain, roughly NE-SW trending, covering >1000 km of the western South Atlantic rifted margin, between parallels 17°S and 27°S (Fig. 1). It comprises the onshore region adjacent to Santos, Campos, and Espírito Santo offshore basins that includes the Cenozoic Rift System of Southeastern Brazil (Riccomini et al., 2004; Zalán and Oliveira, 2005). The complex evolution of the CMSEB
Existing apatite fission track data
Over the last three decades, >35 AFT thermochronology studies (e.g., Carmo, 2005; Doranti et al., 2008; Doranti-Tiritan et al., 2014; Fonseca, 1993; Fracalossi, 2007; Franco, 2006; Franco-Magalhães et al., 2010; Genaro, 2008; Hackspacher et al., 2007; Hadler et al., 2001; Jelinek et al., 2003; Oliveira et al., 2000; Ribeiro et al., 2011; Silva, 2006, Silva, 2010; Souza et al., 2014) were conducted in the CMSEB, amounting to >500 individual samples (Fig. 4 and Appendix A, for a review see Novo
Methods
The continental drainage divide that forms in rifted continental margins in response to the rift-related establishment of a new baselevel for continental erosion is a unique feature of their topographic configuration (Summerfield, 1991; Bishop, 2007). This continental drainage divide, commonly extending over hundreds to thousands of kilometers parallel to the shoreline, separates seaward-dipping catchments with rivers flowing directly to the baselevel from inland catchments with rivers that
Macro-geomorphological characterization of the CMSEB
The continental drainage divide extends for >2500 km over the CMSEB (Fig. 5). From its southern to its northern extension, the continental drainage divide (CDD) passes through several large-scale morphostructures of southeastern Brazil, including parts of the Serra do Mar, the Serra da Mantiqueira, the Quadrilátero Ferrífero, and the Serra do Espinhaço, in a laterally continuous manner. The Paraná and the São Francisco rivers compose the two major drainage systems draining the inland region
The post-rift exhumation of the CMSEB
The establishment of a new baselevel for continental erosion when rifting leads to the rupture of a continent is a fundamental element in the topographic evolution of a rifted continental margin (RCM) (Braun and van der Beek, 2004). In this situation, baselevel lowering along the rift axis causes reorganization of the preexisting drainage pattern and the establishment of a continental drainage divide (CDD) (Gilchrist et al., 1994). In addition, the formation of the new baselevel necessarily
Conclusion
We perform quantitative topographic analysis and use apatite fission track available data to demonstrate how the first order topography and the denudation pattern varies along a segment of the Brazilian South Atlantic coast, more specifically throughout the well-known escarpment system of the Serra do Mar and Serra da Mantiqueira, and the adjacent northeastern segment that includes the Serra do Espinhaço and the Serra do Caparaó. We show that, similar to other mature rifted settings, the
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES, the research fund of the Brazilian Ministry of Education) – Finance code 001 (n° 88887.370562/2019-00). The first author thank Fundação de Amparo Pesquisa do Estado de Minas Gerais (FAPEMIG) for the Ph.D. scholarship funding. The second author had support from CAPES under a CAPES-PrInt Postdoctoral fellowship (n° 88887.508590/2020-00). We also thank Cristina Persano and Mark Wildman for
References (152)
- et al.
Evolution of polycyclic basement complexes in the Araçuaí Orogen, based on U–Pb SHRIMP data: Implications for Brazil–Africa links in Paleoproterozoic time
Precambrian Res.
(2007)
- et al.
Tectonosedimentary evolution of the Resende and Volta Redonda basins (Cenozoic, central segment of the Continental Rift of Southeastern Brazil)
J. S. Am. Earth Sci.
(2020)
- et al.
Topographic controls on erosion rates in tectonically active mountain ranges
Earth Planet. Sci. Lett.
(2002)
- et al.
The south american retroarc foreland system: the development of the Bauru Basin in the back-bulge province
Mar. Pet. Geol.
(2016)
- et al.
Thermal annealing of fission tracks in apatite 2. A quantitative analysis
Chem. Geolo. Isotope Geosci. Sect.
(1987)
- et al.
Multi-chronometer thermochronological modelling of the late Neoproterozoic to recent tT-evolution of the SE coastal region of Brazil
J. S. Am. Earth Sci.
(2019)
- et al.
Evolution of the South Atlantic passive continental margin in southern Brazil derived from zircon and apatite (U–Th–Sm)/He and fission-track data
Tectonophysics
(2013)
- et al.
Denudation history and landscape evolution of the northern east-Brazilian continental margin from apatite fission-track thermochronology
J. S. Am. Earth Sci.
(2014)
- et al.
The onset of flood basalt volcanism, Northern Paraná Basin, Brazil: a precise U–Pb baddeleyite/zircon age for a Chapecó-type dacite
Earth Planet. Sci. Lett.
(2011)
- et al.
Elevated, passive continental margins: not rift shoulders, but expressions of episodic, post-rift burial and exhumation
Glob. Planet. Chang.
(2012)
The zeta age calibration of fission-track dating
Chem. Geol.
(1983)
Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: relationships to Gondwana breakup and passive margin development
Gondwana Res.
(2010)
Evolution of reworked Paleoproterozoic basement rocks within the Ribeira belt (Neoproterozoic), SE-Brazil, based on U –Pb geochronology: implications for paleogeographic reconstructions of the são Francisco-Congo paleocontinent
Precambrian Res.
(2010)
A PC compatible Brazilian software for obtaining thermal histories using apatite fission track analysis
Radiat. Meas.
(2001)
Consolidation and break-up of the south American platform in southeastern Brazil: tectonothermal and denudation histories
Gondwana Res.
(2004)
Thermal annealing of fission tracks in apatite: 1. A qualitative description
Chem. Geolo. Isotope Geosci. Sect.
(1986)
Fission-track annealing in apatite: track length measurements and the form of the Arrhenius plot
Nuclear Tracks Radiation Measurements (1982)
(1985)
A natural long-term track annealing experiment for apatite
Nuclear Tracks
(1981)
South Atlantic passive margin evolution: a thermochronology case study from the Rio de Janeiro-três Rios section, SE Brazil
J. S. Am. Earth Sci.
(2021)
Reactivated shear zones: a case study in a tectonic superposition zone between the Southern Brasília and Ribeira orogens, southeastern Brazil
J. S. Am. Earth Sci.
(2021)
Differential Phanerozoic evolution of cratonic and non-cratonic lithosphere from a thermochronological perspective: São Francisco Craton and marginal orogens (Brazil)
Gondwana Res.
(2021)
Paraná Magmatic Province–Tristan da Cunha plume system: fixed versus mobile plume, petrogenetic considerations and alternative heat sources
J. Volcanol. Geotherm. Res.
(2002)
Thermotectonic history of the Maastrichtian reservoir in Campos basin
Mar. Pet. Geol.
(2018)
Thermotectonic history of the southeastern Brazilian margin: evidence from apatite fission track data of the offshore Santos basin and continental basement
Tectonophysics
(2016)
Connecting the Araçuaí and Ribeira belts (SE–Brazil): progressive transition from contractional to transpressive strain regime during the Brasiliano orogeny
J. S. Am. Earth Sci.
(2018)
From Rodinia to Gondwana: a review of the available evidence from South America
Gondwana Res.
(2003)
Tectonic setting of the Taubaté Basin (Southeastern Brazil): Insights from regional seismic profiles and outcrop data
J. S. Am. Earth Sci.
(2013)
Post-rift reactivation of the onshore margin of Southeast Brazil: evidence from apatite (U–Th)/He and fission-track data
Earth Planet. Sci. Lett.
(2011)
Controls on denudation along the East Australian continental margin
Earth Sci. Rev.
(2021)
Unravelling a Proterozoic basin history through detrital zircon geochronology: the case of the Espinhaço Supergroup, Minas Gerais, Brazil
Gondwana Res.
(2012)
Tectonics and stratigraphy of the East Brazil Rift system: an overview
Tectonophysics
(1992)
Post-miocene topographic rejuvenation in an elevated passive continental margin not characterized by a sharp escarpment (northern end of the Mantiqueira range, Brazil)
Geomorphology
(2021)
The Alegre Lineament and its role over the tectonic evolution of the Campos Basin and adjacent continental margin, Southeastern Brazil
J. S. Am. Earth Sci.
(2016)
Neoarchean and Rhyacian TTG-Sanukitoid suites in the southern São Francisco Paleocontinent, Brazil: evidence for diachronous change towards modern tectonics
Geosci. Front.
(2020)
A review of numerical modeling studies of passive margin escarpments leading to a new analytical expression for the rate of escarpment migration velocity
Gondwana Res.
(2018)
South and southeast Brazilian grasslands during late Quaternary times: a synthesis
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2002)
Stratigraphic framework and evolution of the Cretaceous continental sequences of the Bauru, Sanfranciscana, and Parecis basins, Brazil
J. S. Am. Earth Sci.
(2016)
Denudation rates of the Southern Espinhaço range, Minas Gerais, Brazil, determined by in situ-produced cosmogenic beryllium-10
Geomorphology
(2013)
Rhyacian (2.23–2.20 ga) juvenile accretion in the southern São Francisco craton, Brazil: geochemical and isotopic evidence from the Serrinha magmatic suite, Mineiro belt
J. S. Am. Earth Sci.
(2010)
Siderian to Rhyacian evolution of the Juiz de Fora Complex: Arc fingerprints and correlations within the Minas-Bahia Orogen and the Western Central Africa Belt
Precambrian Res.
(2021)
Phanerozoic cooling history of Archean/Paleoproterozoic basement in the southern Espinhaço range, southeastern Brazil, through apatite fission-track analysis
J. S. Am. Earth Sci.
(2019)
Fission track analysis of apatites from São Francisco craton and Mesozoic alkaline carbonatite complexes from central and southeastern Brazil
J. S. Am. Earth Sci.
(1997)
Kinematic evolution of the Araçuaí-West Congo orogen in Brazil and Africa: nutcracker tectonics during the Neoproterozoic assembly of Gondwana
Precambrian Res.
(2006)
Transamazonian orogeny in the Southern São Francisco craton region, Minas Gerais, Brazil: evidence for Paleoproterozoic collision and collapse in the Quadrilátero Ferrífero
Precambrian Res.
(1998)
Functional relationships between denudation, relief, and uplift in large, mid-latitude drainage basins
Am. J. Sci.
(1970)
Brazilian structural provinces: an introduction
Earth Sci. Rev.
(1981)
The instability of continental passive margins and its effect on continental topography and heat flow
J. Geophys. Res. Solid Earth
(2013)
Long-term landscape evolution: linking tectonics and surface processes
Earth Surf. Process. Landforms J British Geomorphol. Res. Group
(2007)
Birth of the East African Rift System: nucleation of magmatism and strain in the Turkana Depression
Geology
(2019)
Response to comment by Japsen et al., on "a review of numerical modeling studies of passive margin escarpments leading to a new analytical expression for the rate of escarpment migration velocity"
Gondwana Res.
(2018)
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