This work constitutes an example of intraplate application of the modern concept of Structural Geomorphology, which characterizes landforms and drainage patterns within the framework of the neotectonics of the Amazon region. The neotectonics conception adopted here comprises the various structural systems, the sedimentary 'sequences, the land systems and the pattern and anomalies of drainage which were developed during the Upper Terciary and Quatemary. Controversy is particularly intensive over the channel of the Amazon river, between the cities of Manaus and Belém, where plains are found in uplifted areas and also a large diversity of drainage patterns and anomalies. The main goal of the work is to establish a correlation between the complex geomorphological patterns and the structures derived from the transcurrent movements of the Miocene-Pliocene and Upper Pleistocene-Holocene. This implies in a revision of the concepts based on morphoclimatic conditions or domain of vertical movements. The scale of the geomorphological problems dictated the methodology, on a regional basis, which led to the characterization of six morphotectonic compartments as follows: Manaus-Nhamundá, Tupinambarana, Baixo Tapajós, Comandai, Gurupá e Marajoara. 1. The Manaus-Nhamundá compartment shows system landforms with hills where remnants of an erosion surface are present; it is found in the sediments of the Alter do Chão Formation and is controlled by compressive structures of the Upper Terciary. The trellis-type drainage pattern dips southeastward and the more important rivers follow NW-SE normal faults of Quatemary age. 2. The Tupinambarana compartment has a NE-SW rectangular shape. It comprises low relief gradients associated to a strong structural control of the drainage seen on the linear channels of rivers, linear borders of lakes and anomalies of the arch- and elbow of capture types which are derived from the NE-SW lineaments connected to less developed E-W lineaments. The NE-SW lineaments are interpreted as dextral strike-slip faults while the E-W lineaments represent normal faults, both as Quatemary age. 3. The Baixo-Tapajós compartment is characterized by relief of various types - cuesta, dome, volcanic and uplifted blocks which are morphostructures in advanced stages of erosion. Relief and drainage show control by two neotectonic systems: NE-SW and ENE-WSW folds of Upper Terciary age which gave rise to a strong relief gradient shown in landform systems with a widespread regional distribution including cuestas and the Monte Alegre dome. The Quaternary structures are defined by triple junctions of normal and strike-slip faults. 4. The Comandai compartment is observed on the northern margin of the Amazon river with cuestas systems, a morphology defined by the channels of the Jaraú river and its tributaries which cut those structures giving a trellis-type pattern.. The other important feature of this compartment is the residual hills system with flat tops at about 300 m and intrenched streams which channels are modelled by structures giving anomalies of the arch- and elbow of capture types. The landform hills forro a planation surface at 100 m with rectilinear slopes giving a dendritic-rectangular pattern of drainage. Structural control of the relief and drainage as well as the anomalies in the channel of the Amazon river are found to be related to the transcurrent branch of the Baixo-Tapajós triple junction. The other interpretation of those structures relates to the origin of the hills to remnants of the Gurupá Arch therefore associated to normal faults of Mesozoic age. 5. The Gurupá compartment shows, as an important feature in the Amazon plain, the archipelago in the mouth of the Amazon river with an anastomotic pattern. Islands here show NE-SW orientation and are rectangular in shape. In the continent, relief is the flat interfluvial surface type in the sandstones of the Alter do Chão Formation and in the sediments of the Barreiras Group. Drainage shows a subdendritic pattern. Tectonic activity is registered since the Mesozoic with NE-SW dextral strike-slip faults along which pull-apart basins were formed. These tectonics were active until the Upper Terciary. The landscape is modelled by dextral strike-slip systems with orientation NE-SW and ENE-WSW normal faults. 6. The Marajoara compartment comprises the Marajó Island and the northeastern region of the State of Pará with estuarine morphology and was subjected to subsidence tectonics since the Mesozoic. NW-SE normal faults were developed during the Upper Terciary and these and dextral strike-slip faults controlled the deposition of the Pirabas-Barreiras sequences. These movements were active still in the Quatemary and explain the coastal landforms. The development of these compartments is not directly related to the evolution of the northern and westem borders of the South-American plate.
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