Tectonics and paleogeography of the Marajó Basin, northern Brazil

João B S Costa,Ruth L Bemerguy,Javier M C Villegas,Yociteru Hasui,Adilson V Soares-Júnior

doi:10.1590/s0001-37652002000300013

Abstract

The Marajó Basin area presents geologic and geomorphologic features chiefly due to the Mesozoic extension and post-Miocene neotectonics. The extension event with an Early and a Late Cretaceous phases originated four sub-basins that constitutes the Marajó Basin, with a thick continental clastic sequence showing marine influence. NW and NNW normal faults and NE and ENE strike-slip faults controlled the basin geometry. The extension, related to the Equatorial Atlantic opening, propagated into the continent along crustal weakness zones of the Precambrian Tumucumaque, Amapá and Araguaia orogenic belts. The neotectonic event is a strike-slip regime which developed transtensional basins filled in by Upper Tertiary shallow marine (Pirabas Formation) and transitional sequences (Barreiras Group), followed by Quaternary fluvial deposits and transitional sequences derived from the Amazon and Tocantins rivers and the Marajoara estuary. The current landscape has a typical estuarine morphology. The coast morphology presents sea-cliffs on transitional Upper Tertiary sequences, while inwards dominate hills sustained by Mid-Pleistocene lateritic crust, with a flat erosive surface at 70 m. In the eastern Marajó Island several generations of paleochannels associated with fluvial-estuarine sequences are recognized, while a fluvial-marine plain is widespread on its western side.

Highlights

Beneath a thick Tertiary sequence in the Marajó Island and adjacent areas there is a large extensional Mesozoic rift system which consists of four major sub-basins (Mexiana to the north, Limoeiro in the center, and Cametá and Mocajuba in the south; Figure 1), evidenced from gravity and magnetic data and detailed seismic interpretation (Rezende and Ferradaes 1971, Schaller et al 1971, Miller and Avenius 1986, Carvajal et al 1989)
The tectonic evolution is better understood if considering important aspects of plate dynamics, basin geometry and rift kinematics to clarify the development of the distinct structural compartments as well as their heritage from Precambrian structures
The overall arcuate shape of the Marajó Rift and complex faulting geometry of the sub-basins are believed to be controlled by the combined weak zones of three distinct Precambrian orogenic belts

Summary

Introduction

Beneath a thick Tertiary sequence in the Marajó Island and adjacent areas there is a large extensional Mesozoic rift system which consists of four major sub-basins (Mexiana to the north, Limoeiro in the center, and Cametá and Mocajuba in the south; Figure 1), evidenced from gravity and magnetic data and detailed seismic interpretation (Rezende and Ferradaes 1971, Schaller et al 1971, Miller and Avenius 1986, Carvajal et al 1989). Northern boundaries, respectively with Mexiana and Cametá sub-basins, are defined by the Arari and Tocantins strike-slip fault zones (Figure 2b).

Results

Conclusion