Evolução holocênica dos canais de marés do Delta do Rio Parnaíba (NE do Brasil): uma abordagem hidroacústica e por sensores remotos orbitais

Abstract

The Parnaíba River Delta (PRD) is located on the Equatorial Margin of Brazil. The PRD consists of a wave-dominated delta with tidal influence, representing a rare example of a depositional system that preserves features in natural state. The present work aimed to understand the Holocene evolution of this delta by correlating surface and subsurface features based on the compilation of digital image processing procedures and concepts of sequence stratigraphy and seismostratigraphy. For this were used radar data from Alos Palsar and Landsat 8 images coupled with high-resolution reflection seismic to develop an altimetric and geomorphologic map of the PRD, as well as a seismic analysis of its tidal channel system. The conversion of ellipsoidal height to orthometric height was done to the Alos Palsar radar data and the statistical analysis of spectral bands constrained the most effective RGB compositions to identify fluvial-lacustrine plains, paleodunes, mangrove, beaches and recent dunes. The seismic analysis was done through the description and analysis of seismic lines on the western side of the PRD. The following criteria was considered: reflector patterns, limit surfaces, paleochannel morphology and filling patterns. An altimetric and geomorphological simplified maps were developed. The results indicated the presence of eight types of seismic facies (four variations of parallel to subparallel reflectors, as well chaotic, oblique prograding, wavy and translucent), two paleochannel morphologies (U and V), five types of filling patterns (onlap, prograding, chaotic, complex and diverging) and two seismostratigraphic units. The analysis and integration of the different information allows us to propose three stages of sea level for the interpreted data set. From the base to the top, they are: low sea level, transgressive and high sea level. The present work consists of a pioneer initiative on the PRD region, since previous works correlating seismostratigraphy and high-resolution reflection seismic were performed only on the offshore portion of the PRD. The results contributed to the advance of the knowledge regarding the geological evolution of the coastal sector of the Equatorial margin that is still poorly understood.