Tectonics and paleogeography along the Amazon river

Costa, Joao Batista Sena; Bemerguy, Ruth Léa; Hasui, Yociteru; Borges, Maurício da Silva

doi:10.1016/s0895-9811(01)00025-6

Cited by 102 publications

(65 citation statements)

References 9 publications

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“…However, the data presented here allows to clearly state that tectonics had a strong control on the local deformation of these deposits. These data conform to structural studies, which have proposed a complex evolution for this area, including the development of sets of NW/SE and NNW/SSE-oriented normal faults cut by NE/SW and E/W-oriented strike-slip faults (Igreja et al 1990, Costa et al 2001). …”

Section: Concluding Discussionsupporting

confidence: 82%

“…The record of faults and fractures in Cenozoic deposits of the Bragantina Zone is not new (Katzer 1933, Ackermann 1964. Tectonic models combining normal and strike-slip faults have been proposed for this area (Igreja et al 1990, Costa et al 2001. These studies are mostly based on the analysis of drainage systems and morphological aspects of coastal cliffs, while geological field evidence remains inadequate to test the models.…”

Section: Introductionmentioning

confidence: 99%

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Delineating shallow Neogene deformation structures in northeastern Pará State using Ground Penetrating Radar

Rossetti

2003

An. Acad. Bras. Ciênc.

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The geological characterization of shallow subsurface Neogene deposits in northeastern Pará State using Ground Penetrating Radar (GPR) revealed normal and reverse faults, as well as folds, not yet well documented by field studies. The faults are identified mostly by steeply-dipping reflections that sharply cut the nearby reflections causing bed offsets, drags and rollovers. The folds are recognized by reflections that are highly undulating, configuring broad concave and convex-up features that are up to 50 m wide and 80 to 90 ns deep. These deformation structures are mostly developed within deposits of Miocene age, though some of the faults might continue into younger deposits as well. Although the studied GPR sections show several diffractions caused by trees, differential degrees of moisture, and underground artifacts, the structures recorded here can not be explained by any of these "noises". The detailed analysis of the GPR sections reveals that they are attributed to bed distortion caused by brittle deformation and folding. The record of faults and folds are not widespread in the Neogene deposits of the Bragantina area. These GPR data are in agreement with structural models, which have proposed a complex evolution including strike-slip motion for this area from the Miocene to present.

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Section: Concluding Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Delineating shallow Neogene deformation structures in northeastern Pará State using Ground Penetrating Radar

Rossetti

2003

An. Acad. Bras. Ciênc.

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“…A conventional molecular clock of 2% per million years for the cytochrome b gene (Avise, 2000) suggests that this divergence is between 0.6 and 1.65 millions of years (myr) old, much younger than the estimated age of the initial connection of the Amazon with the Atlantic, 10-12 myr old (Hoorn, 1994;Nittrouer et al, 1996;Costa et al, 2001). Thus, vicariance alone cannot explain the observed pattern, and dispersal from one area to the other after the formation of the Amazon is probably involved in speciation of western Atlantic Halichoeres.…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial DNA and Color Pattern Variation in Three Western Atlantic Halichoeres (Labridae), with the Revalidation of Two Species

Rocha¹

2004

Copeia

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Genetic surveys of widely distributed marine species often find previously undetected biodiversity. In the present study, populations of three species of Halichoeres were sampled across their entire geographical ranges: Halichoeres cyanocephalus and Halichoeres maculipinna were sampled on both sides of the Amazon freshwater outflow, the main biogeographic barrier in the tropical western Atlantic; and Halichoeres garnoti was sampled in the Caribbean and Bermuda. Genetic divergences between populations separated by the Amazon ranged from 2.3% in H cyanocephalus to 6.5% in H. maculipinna. There is inconsistency between color differences and genetic partitions in the species surveyed. The color differences between populations of H cyanocephalus and H maculipinna correspond to deep genetic partitions at the cytochrome b locus. However, genetic similarity at this same locus was observed between populations of H. garnoti with striking color differences. Based on the combination of the observed genetic differences with diagnostic color differences, the BraziUan species Halichoeres dimidiatus (Agassiz) and Halichoeres penrosei Starks, 1913 are revalidated. In addition, a neotype is designated to H cyanocephalus (Bloch, 1791), to clarify its taxonomic status and type locaUty. All species analyzed have a similar larval dispersal potential, but varying degrees of genetic divergences were observed, indicating that benthic stage ecology may also play a role in speciation in this group.

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“…To the north of the study area, Costa et al (2001) considers that the neotectonic evolution is marked by two sets of structures, NW-trending normal faults which control the deposition of Late Tertiary deposits, and E-W trendind rightlateral strike-slip faults controlling the deposition of LatePleistocene to Holocene alluvial deposits. In this context, N-S oriented structures (the Tocantins-Araguaia and parallel faults) behave as reverse faults whereas the NW-oriented structures (as the Picos-Santa-Inês Lineament) behave as normal faults.…”

Section: Study Areamentioning

confidence: 99%

Regional scale analysis of landform configuration with base-level (isobase) maps

Grohmann¹,

Riccomini²,

Chamani³

2011

Hydrol. Earth Syst. Sci.

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Abstract. Base-level maps (or "isobase maps", as originally defined by Filosofov, 1960), express a relationship between valley order and topography. The base-level map can be seen as a "simplified" version of the original topographic surface, from which the "noise" of the low-order stream erosion was removed. This method is able to identify areas with possible tectonic influence even within lithologically uniform domains. Base-level maps have been recently applied in semi-detail scale (e.g., 1:50 000 or larger) morphotectonic analysis. In this paper, we present an evaluation of the method's applicability in regional-scale analysis (e.g., 1:250 000 or smaller). A test area was selected in northern Brazil, at the lower course of the Araguaia and Tocantins rivers. The drainage network extracted from SRTM30 PLUS DEMs with spatial resolution of approximately 900 m was visually compared with available topographic maps and considered to be compatible with a 1:1,000 000 scale. Regarding the interpretation of regional-scale morphostructures, the map constructed with 2nd and 3rd-order valleys was considered to present the best results. Some of the interpreted base-level anomalies correspond to important shear zones and geological contacts present in the 1:5 000 000 Geological Map of South America. Others have no correspondence with mapped Precambrian structures and are considered to represent younger, probably neotectonic, features. A strong E-W orientation of the base-level lines over the inflexion of the Araguaia and Tocantins rivers, suggest a major drainage capture. A N-S topographic swath profile over the Tocantins and Araguaia rivers reveals a topographic pattern which, allied with seismic data showing a roughly N-S direction of extension in the area, lead us to interpret this lineament as an E-W, southward-dipping normal fault. There is also a good visual correspondence between the base-level lineaments and Correspondence to: C. H. Grohmann (guano@usp.br) geophysical anomalies. A NW-SE lineament in the southeast of the study area partially corresponds to the northern border of the Mosquito lava field, of Jurassic age, and a NW-SE lineament traced in the northeastern sector of the study area can be interpreted as the Picos-Santa Inês lineament, identifiable in geophysical maps but with little expression in hypsometric or topographic maps.

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Tectonics and paleogeography along the Amazon river

Cited by 102 publications

References 9 publications

Delineating shallow Neogene deformation structures in northeastern Pará State using Ground Penetrating Radar

Delineating shallow Neogene deformation structures in northeastern Pará State using Ground Penetrating Radar

Mitochondrial DNA and Color Pattern Variation in Three Western Atlantic Halichoeres (Labridae), with the Revalidation of Two Species

Regional scale analysis of landform configuration with base-level (isobase) maps

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