GEOMORPHOLOGICAL AND GEOPHYSICAL EVIDENCES FOR
NEOTECTONICS, CENTRAL AND SOUTHERN BRAZIL
Paulo César Soares1, Silvana Bressan Riffel2, Alberto P. Fiori 3
1
FUNPAR/UFPR, Projeto Falhas, Curitiba, p_soares@terra.com.br
2
School of Earth Sciences, The University of Queensland, sillbr@gmail.com
3
UFPR, Projeto Falhas, Curitiba, fiori@ufpr.br
Abstract
Paleosurfaces, correlative deposits, ages, lineaments, heat flow and Curie surface are
used in an integrated way to reach some conclusions about the complex histories of uplift,
denudation and tectonic movements in the Meridional plateau region, including coastal
ranges. The South American peneplane is taken as reference surface and contoured showing
differential uplift. Transcurrent faults in correlative deposits, recorded in field indicate
concentrated zones of deformation. Heat flows and low depth of estimated Curie surface
confirms heat transfer in narrow zones. The Lancinha lineament (Cubatão - Alem Paraiba) is
the focused fault in the work area. Active tectonics and heat flux are associated with crustal
flexural deformation, modified by differential movement along fault zones.
INTRODUCTION - The Late Cretaceous stable conditions recorded from fissiontrack ages (90-60 Ma, Gallagher et al., 1994; Hiruma et al., 2010) refer to the Bauru
sedimentation cycle in SE South America. It is followed by Paleocene uplift ages (60-40 Ma)
denudation and cooling. A late Eocene age for South ameriacan peneplane is concluded based
in geological record of Chaco Paraná and Santos basins and FTA.
Fig. 1 – Location of investigated region with Paraná basin coastal
ranges and Miocene interior sea.
METHODS - Data and information from tectonic events,
geoforms associated to correlative residual weathering
and
sediments over paleosurfaces from southeastern South America
(fig. 1) are compared to potential correlative sequences either in
interior (Chaco Parana) as marginal basin (Santos) and to regional
rifting basins (Taubaté, Curitiba). Uplift and quiescence times are
interpreted from fission track ages (FTA) in literature. Heat flow
(HF) results are regionally extended bounded by lineaments in a region of more dense
information (PR, SC). Deepness of Curie (DC) surface was estimated from magnetic data.
RESULTS - South American Peneplane, as a surface of minimum hydraulic erosion
with maximum chemical erosion processes, needs a long time of tectonic quiescence. The
record of Paleocene to late Eocene erosion and weathering in the continent is indicative of
extensive erosion ander warm climate and uplift. In mid Eocene uplift slown down and
climate become warmer, from Central Brazil to south down to 34oS longitude as seen in
Paraná and Uruguay; fossil termites nests is a common feature. Correlative reddish siliclastic
deposits occur in Chaco-Parana interior and Santos and Pelotas basin (Pereira & Macedo
1990). In Paraná, the Fe-laterite peneplane precedes Curitiba plateau and Serra do Mar
formation. In Uruguay, the Fe-lateritic paleosurface precedes the calcrete-silcrete paleosurface
and Fray Bento Fm of Late Oligocene age (Ubilla, 2004). Both precede the Miocene
transgression (Camacho Fm; Perea & Martinez 2004).
First pediplanation (Pd2, Bigarella and Ab Saber 1956) and Curitiba rift basin fill
(Salamuni et all. 2003) are pene-contemporaneous. High plateaus pediplanes as Japi and
Campos are considered as result o extensive pediplanation (Pd2), in view of remaining
insebergs and of Fe poor and Al-silica rich residual weathering mantle (Modenesi-Gautieri et
al 2011). In similar way kaolin residual deposits are found over Pd2 remnants over gneiss
and volcanic rocks in Serra do Mar. A second pediplane is preserved locally everywhere in
region, and referred as Pd1, probably Miocene. These deposits are faulted in Curitiba plateau.
The big escarpment from Serra do Mar to coastal plain is the result of back strip of this PD1
paleosurface.
Uplift from Oligocene - This uplift and erosion cycle have two main step: mid
Oligocene (Santos platform erosion and faulting) and Pliocene (Late Miocene) to present
(platform prograding wedge). Fission track analysis (Gallagher et al., 1994; FrancoMagalhaes 2010) indicate that East Paraná larger uplift was preceding SAP (40-60 Ma) and
during late Miocene and Pliocene (last 20 Ma). This means that the main uplift was after Pd2
pediplanation and even more recent, after PS1, which agrees very well with geomorphologic
and field observation of altimeric position of paleosurface and deposits, including the
prominent escarpment sculptured on PS1 and their inselbergs. Faulting affecting both are
recovered in field.
Structural contour of PSA and heat flow - Contour map (figure ) shows a high bulge in
Central Paraná and Santa Catarina, mainly forced by points in Santos Basin and in continent
interior. Heat flow map (from Soares et al 2011) shows high values associated with higher
uplift.
Figure 2
Left - Uplift of South
America peneplane (SAP) during
Neogene
(grey
<100m;
green/brown=600m;pale=over
1300 m) Along coastal range SAP
altitudes are underestimated by
absence of remains (SP and PR>
2000m; SC>1700). Right - Heat
flow from oil
wells in Parana
basin estimated by many authors (
mainly Hurter and Pollack 1996).
The colored area north of SC is
detailed in next figure)
The South American paleosurface is characterized by intense planation, chemical
leaching, Fe-laterization crust, summit positioning, implying a long time of tectonic
quiescence during warm and semi humid climate. In some place it is covered by ferruginous
quartz conglomerate; other places, gravel, sands and gray clays cover the surface.
Figure 2 Left- Lineaments from many sources (Soares et al. 2009), the two main correspond to Lancinha (NESW) and Itapirapuã (NNE) faults in basement (at the extreme northeast of the area (green line); Center – Depth
of Curie surface oscillating from 10 (red/purple) to 40 (green/blue) km indicating narrow zones of high heat
flow; right – contour of heat flow estimates from deep wells (mainly from Hurter .& Pollack 1996), showing
heat flow in the range 40 to 80 mW/m2 (blue/purple = 56 mW/m2); high heat flow are associated to fault zones
(square delineates the area of left figures) (partial maps from Soares et al. 2011).
DISCUSSION AND CONCLUSIONS - In the continental interior, lateritic South
American peneplane surface are documented in isolated inselbergs and plateaus with warm
climate indicator until Uruguay and Chaco. In coastal ranges it was uplifted and eroded
before and during the emplacement of the rift basins (Oligocene), because was not preserved
as basement. The subsequent large erosion event, mostly under semi-arid and cold climate,
have constructed extensive pediplane surfaces in Serra da Mantiqueira (Campos Surface) and
Serra do Mar (PD2 in Paraná). At this time climate changed abruptly, depositing feldspatic
sands and green muds with caliche paleosoils (Guabirotuba Fm in Curitiba basin, and Taubaté
Group) toward coastal ranges. Toward Paraná basin interior, records of Late Oligocene have
similar lithologies and a rich fossil record in Fray Bentos Fm in Uruguay (Ubilla, 2004). The
larger uplift event may have been after Pd1 pediplanation, Miocene transgression and Pd2
pediplanation, during late Miocene to Pliocene, feeding the prograding clastic wedge in
Santos and documented in FTA and annealing zone. At the low Paraná-Paraguay-Uruguay
basin, early to mid Miocene sea cover continental cold and semiarid deposits, up to 10 Ma.
They are extensively exposed and transitional to mid Pleistocene alluvial deposits (Perea &
Martinez 2004). This is considered the main time of neotectonic activity which maintain
active heat flow in narrow zones along crustal discontinuities.
CONCLUSIONS - Tectonic activity are powerful generator of heat in faults associated with
continental uplift. The heat flow may double in narrow fault zones. Paraná basin and neighbor
regions presents active uplift and faulting as deduced from paleosurfaces succession and
altimetry positioning, mainly during Pliocene and Quaternary, contemporaneous to Quechua
Andean activity, continental plate flexures and marginal basin clastic wedge.
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