Structural Geomorphology in Northeastern Brazil

119 Pages·2020·6.683 MB·English

by  Rubson Maia, Francisco Bezerra

SPRINGER BRIEFS IN LATIN AMERICAN STUDIES
Rubson Maia
Francisco Bezerra
Structural
Geomorphology
in Northeastern
Brazil
123
SpringerBriefs in Latin American Studies
Series Editors
Jorge Rabassa, Lab Geomorfología y Cuaternario, CADIC-CONICET, Ushuaia,
Tierra de Fuego, Argentina
Eustógio Wanderley Correia Dantas, Departamento de Geografia, Centro de
Ciências, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
Andrew Sluyter, Conference of Latin Americanist Geographers, Louisiana State
University, Baton Rouge, LA, USA
More information about this series at http://www.springer.com/series/14332
Rubson Maia Francisco Bezerra
(cid:129)
Structural Geomorphology
in Northeastern Brazil
123
RubsonMaia Francisco Bezerra
Departamento deGeografia Universidade FederaldoRio
Universidade FederaldoCeará Grande doNorte
Fortaleza, Ceará,Brazil Parnamirim, RioGrandedoNorte, Brazil
ISSN 2366-763X ISSN 2366-7648 (electronic)
SpringerBriefs inLatin AmericanStudies
ISBN978-3-030-13310-8 ISBN978-3-030-13311-5 (eBook)
https://doi.org/10.1007/978-3-030-13311-5
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Introduction
In Northeastern Brazil, the relief documents important episodes in the morpho-
tectonic evolution. Organized around paleosurfaces, the region presents diverse
geomorphological compartments derived from tectonic events, such as the
Brasiliano cycle and the breakup between South America and Africa. Both events
generated various structural morphologies. The crystalline massifs that are aligned
according to different shear zones are worthy of note. Other forms are associated
with structural lineaments that control drainage and dissection. The third type are
the Mesozoic Basins affected by uplift. This whole group comprises a complex
morphostructural system, which began to be interpreted from the 1960s as com-
posed of successive levels of terraced paleosurfaces. However, the region has a
great number of Cenozoic deformation structures, especially in sedimentary areas,
sometimes influencing the sediment deposition and erosion.
From this perspective this book discusses the models of geomorphological
evolution of Northeastern Brazil, analyzing their features and limitations with
regard to the suitability of the concepts associated with the Cenozoic tectonic and
thegeochronologyofthegeologicalunits.Italsodealswithaspectsrelatedtorelief,
starting from individualized studies developed in areas with proven Cenozoic
tectonic activity, such as the Potiguar Basin in the states of Ceará and Rio Grande
doNorte.Theanalyticalfocusinvolvestherelationshipbetweentectonicsandrelief
on different scalesand geological times, beit of detail as inthecase ofthe valleys
and karst, or regional as in the case of basins and massifs.
v
Contents
1 The Paradigm of Stable Intraplate Regions and Neotectonics
in Northeastern Brazil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 The Stable Crust Paradigm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 The South American Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Seismicity in Northeastern Brazil. . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 The Causes of Intraplate Seismicity and Examples
of Seismogenic Faults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Present-Day Stress Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5.1 Focal Mechanisms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5.2 Borehole Breakouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5.3 Image Logs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.4 Fault-Slip Data in Quaternary and Miocene
Sedimentary Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 Understanding the Geological Setting of Northeastern Brazil. . . . . . 15
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2 The Borborema Province . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 The Cretaceous Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4 The Neogene–Quaternary Sedimentary Covers . . . . . . . . . . . . . . . 19
2.5 Introduction to Neotectonics in Northeastern Brazil . . . . . . . . . . . 20
2.6 Paleoseismicity in Northeastern Brazil . . . . . . . . . . . . . . . . . . . . . 21
2.7 Miocene to Quaternary Tectonics and Sea-Level Changes. . . . . . . 23
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3 The Geomorphology of the Northeast: Classical and Current
Perspectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.1 Classic Models of Geomorphological Evolution . . . . . . . . . . . . . . 31
3.2 Genetic Aspects of the Relief of Northeastern Brazil:
Classic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
vii
viii Contents
3.3 Synthesis of the Weak Points of the Paleosurface Model . . . . . . . 35
3.4 Current Concepts About the Geomorphology of Northeastern
Brazil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4 The Erosion and Exhumation of Massifs in Precambrian
Shear Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1 Influence of Fault Reactivations on the Relief Evolution
in the Borborema Province . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2 Structural Control of the Relief and Drainage: Examples
from the Borborema Province . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.3 Structural Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.4 Exhumation of the Brasiliana Shear Zones. . . . . . . . . . . . . . . . . . 51
4.5 Differential Erosion and Topographical Inversion . . . . . . . . . . . . . 53
4.6 Granitic Inselbergs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5 The Morphostructural Evolution of Cretaceous Basins. . . . . . . . . . . 71
5.1 Neotectonic Stress Field and Basins Inversion . . . . . . . . . . . . . . . 72
5.2 Geological and Geomorphological Characterization
of the Potiguar Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.3 Extensional Basins and Compressional Tectonics . . . . . . . . . . . . . 75
5.4 Sedimentary Tectonics and Basin Inversion . . . . . . . . . . . . . . . . . 79
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6 Karstic Geomorphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.1 Geological and Environmental Characterization . . . . . . . . . . . . . . 88
6.2 Post-rift Tectonic and Faults in the Potiguar Basin . . . . . . . . . . . . 90
6.3 Karstic Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
7 Neotectonics and River Valleys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
7.1 The Geomorphology of the Northeast: Genetic Aspects . . . . . . . . 103
7.2 Tectonics and Fluvial Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.3 The Morphotectonic Evolution of the Brazilian Northeast. . . . . . . 106
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Chapter 1
The Paradigm of Stable Intraplate
Regions and Neotectonics
in Northeastern Brazil
Abstract Activefaultsinstablecontinentalregionsarelessfrequentthanthosein
plate boundaries but cannot be ignored. These faults can generate earthquakes in
intraplate settings that cause widespread damage in regions where the population
is ill-prepared to cope with them. Intraplate earthquakes are due to many causes
such as reactivation of ancient rifted crust, major terrane boundaries, density and
rigiditycontrast,heatflow,andfaultintersection.Thepresent-daystressfieldinthe
SouthAmerican plateroughly followsthetrajectoriesoftheabsoluteplate,i.e.,is
mainlyE-W-oriented.InNortheasternBrazil,thestressregimeismainlystrike-slip
andthemaximumhorizontalstressesfollowtheequatorialcoastline.Northeastern
Brazil is one of the most seismically active parts of the South American stable
continentalregionandpresentsearthquakesuptomagnitudeMb=5.2.Seismicity
isconcentratedintheuppercrustdowntoadepthof12kmandilluminatesactive
faultsupto40kmlong.Activefaultseitherreactivateshearzonesorregionalfoliation
andquartzveinsorcutacrossthepreexistingtectonicfabric.
· · ·
Keywords Faults Neotectonic Northeastern Brazil
1.1 TheStableCrustParadigm
Several names have been used to describe intraplate areas. These names include
passivemargins,stablecontinentalmargins,stablecontinentalcrusts,stableregions,
andcratons.Mostofthesenamesarerelativedefinitionsthatcompareintraplateareas
withactivetectonicplateboundaries.However,partofthescientificcommunitystill
seesintraplateareasasdevoidoftectonicactivity.
Intraplateareasoccurawayfromplateboundariesandhavenotexperiencedany
major orogenic cycle since the Cretaceous or any major rifting episode since the
Paleogene (Schulte and Mooney 2005). Intraplate areas exhibit a long period of
seismic recurrence and poor surface expression of earthquakes. Active faults are
rareinintraplateareaswhencomparedwiththosethatoccuratplatemargins.The
period of recurrence of active faults in intraplate areas can range from 10,000 to
©TheAuthor(s),underexclusivelicensetoSpringerNatureSwitzerlandAG2020 1
R.MaiaandF.Bezerra,StructuralGeomorphologyinNortheasternBrazil,
SpringerBriefsinLatinAmericanStudies,
https://doi.org/10.1007/978-3-030-13311-5_1
2 1 TheParadigmofStableIntraplateRegions…
100,000yearsormore(Croneetal.1997).Forexample,onlytengreatearthquakes
producedsurfacerupturesinintraplateregionsinthetwentiethcentury(Croneetal.
2003).
However,despitethelowseismicity,evenmoderateseismicactivityinintraplate
settingscouldcausewidespreaddamagebecausethebuildingsandthepopulations
arelesspreparedtocopewithit(HanksandJohnston1992).Increasingly,investi-
gations have indicated that although the tectonic activity in intraplate areas is not
comparablewiththatobservedatplateboundaries,thisintraplateactivitycouldnot
be ignored. An increasing number of studies have supported that intraplate areas
aremoreactivethanpreviouslysupposed(e.g.,BezerraandVita-Finzi2000;Japsen
etal.2012;Gurgeletal.2013).Thesestudieshavepointedouttheoccurrenceofan
importantpost-riftactivitysincethelastmajorriftingphaseintheearlyCretaceous.
Theneedtoimproveknowledgeofthetectonicactivityandlandscapeevolution
in intraplate areas has increased significantly. Several scientific gaps still remain
andincludethefollowing:(1)understandhowfaultpropagationinfluencesediment
depositionanderosionoflandforms,aswellasthecreationofnewrelief;(2)The
sedimentationandmorphologyhavebeenattributedtofactorssuchastectonicsand
climate (Bezerra et al.2008). However, the contribution of individual factors such
astectonicsandclimateinshapingthemorphologyandsedimentsupplyhasbeen
difficult to isolate (Bezerra et al. 2007); (3) There is an overall acceptance that
somekindoftectonicactivitycouldhaveoccurredduringsedimentdeposition,but
muchhastobeinvestigatedabouthowsedimentshavebeendepositedanddeformed
(DentithandFeatherstone2003).
1.2 TheSouthAmericanPlate
The relatively stable interior of the South American plate is limited by the Andes
tothewestandbyMARtotheeast.Theplateinterioriscomposedofacontinental
crustandanoceaniccrust(Fig.1.1).TheSouthAmericanplateiscurrentlymoving
westward away from the middle ocean ridge and against the Nazca Plate and is
subjectedtocompressionfrombotheastandwest.Thevelocityofspreadingatthe
ocean ridge is ~34 mm/year. The Nazca Plate, however, moves toward the South
AmericanPlateatavelocity~84mm/year(DeMetsetal.1990).
The target area of this book is the Atlantic margin of the South America plate,
whosegeometryandlimitsarewellknown.Theeasternandwesternedgesofthis
platearebetterdefinedthanitsnorthernandsouthernboundaries(MinsterandJordan
1978;DeMetsetal.1990;MeijerandWortel1992).Theeasternboundaryismarked
byshallowseismicityalongthemid-oceanridgeintheSouthAtlantic,wherespread-
ing rates ranges from 32 to 38 mm/year at 5 S to 40 S (Gordon and Jurdy 1986).
Along the western boundary, the Nazca plate subducts at a rate of approximately
84–90 mm/year along a trench ~6000 km long (Dewey and Lamb 1992). In the
northernmarginoftheplate,theboundaryisbroadlydefinedbytheCaribbeanand
NorthAmericanplates(DeMetesetal.1990).Thesouthernboundariesoccuralong