Banca de DEFESA: GENISSON PANTA DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GENISSON PANTA DA SILVA
DATE: 04/03/2022
TIME: 15:30
LOCAL: Webconferência
TITLE:

Geomorphological expression of base level fall in the Lower São

Francisco

KEY WORDS:

fluvial incision, semiarid, morphometry, planation surface.

PAGES: 122
BIG AREA: Ciências Humanas
AREA: Geografia
SUMMARY:

A large number of studies of flat surfaces on high-elevation
passive margins have listed river erosion over bedrock as one of
the determining factors in the long-term evolution of the
landscape. However, in low-elevation hinterlands over exposed
shield, it is often said that rivers play a supporting role in relief
delineation. Rivers, in this context, are routinely described as
transporting agents for pre-weathered material. However,
physical mechanisms involved in the mechanics of river erosion
in rocky beds testifies its importance goes beyond the transport
of sediments. This study aims to analyze the fluvial topography
of bedrock rivers that drain the Southern Sertaneja Depression,
a pervasive, low-elevation flat surface over the Proterozoic
shield that borders the Borborema Plateau, in the semi-arid
region of Northeast Brazil. We sought to investigate the
morphology of the longitudinal profiles, map knickpoints,
estimate the magnitude and spatial distribution of the vertical
incision of river valleys and evaluate the contribution of
structural controls on these morphologies. All these analyzes
were based on morphometric techniques based on a Digital
Elevation Model (DEM), such as the extraction of the
Normalized Steepness Index (K sn ) and the Slope-Length
Relation (SL), in addition to the quantification of the slope angle
of the hillslopes, analysis of photolineaments of relief and
drainage, integral and hypsometric curve, local relief, among
others. The target rivers of this study are all tributaries of the left
bank of the lower course of the São Francisco River, in the
region of its canyon. The hypothesis that guides this study is
that a lowering of the base level generated an incision wave that
is propagating through the São Francisco River and its tributary
network in the flat Proterozoic terrains of the Southern Sertaneja
Depression. With the morphometric analyses, the existence of 

this supposed wave of incision in the tributaries of the São
Francisco was demonstrated. This process produces a clear
pattern of base level fall in the landscape of the study area, with
the increase of the slope of the channels, hillslopes and the
formation of hangig valleys downstream of the main ruptures,
which form a fractal at various scales. The valleys and ridges
are subordinated to the structural heritage of the basement, as
well as the sinuosity of the channels and the confluence angle. It
has been suggested, based on independent evidence, that the
São Francisco epigeny originated in the Eocene and the incision
wave that is observed in the valleys today was formed after this
period.

BANKING MEMBERS:
Externo à Instituição - ANTONIO CARLOS DE BARROS CORRÊA - UFPE
Presidente - 1891214 - KLEYTHON DE ARAUJO MONTEIRO
Externa ao Programa - 1574934 - NIVANEIDE ALVES DE MELO FALCAO