Geochronology of surficial covers on low terreces in the river mouths of Una/Pardo (BA), related to marine transgressions and regressions arising from holocene climate pulses

Author(s)

Vinícius Borges Moreira

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
• Defense date: 2021-12-15

Examining board members

Archimedes Perez Filho; María Victória Soto Bäuerle; Kleython de Araujo Monteiro; Fernando Nadal Junqueira Villela; Regina Célia de Oliveira

• Advisor: Archimedes Perez Filho

Abstract

The occurrence of surficial covers at different levels of low terraces located in the coastal zone can be understood as remnants or testimonies of environmental conditions different from the current one. In this sense, this work aims to analyze its genesis considering the hypothesis of climatic pulsations occurring during the Holocene. Such processes would be responsible for marine transgression and regression, in different magnitudes, originating levels of low terraces and such covers. To test this hypothesis, the hydrographic basins of the Una and Pardo rivers, located in the southern region of Bahia state, were chosen to apply the proposed methodologies. Absolute dating by Optically Stimulated Luminescence - OSL is the main technique to recognize the period of deposition of surficial covers, due to its high degree of chronological accuracy and suitability to the type of material collected. Morphometric analyzes carried out in the lower course of the Una and Pardo rivers, spatialization of terrace levels, granulometric analysis, chemical analysis, morphostratigraphic and morphoscopic analysis of surficial covers are auxiliary methodologies to interpret the characteristics of deposits correlating with variations in the relative sea level, being fundamental to understand the coastal landscape evolution. From the application of these methodologies, the depositional period of staggered marine terraces was characterized and identified, as follows: Level III - elaborated at the end of the Pleistocene and transition with the lower Holocene (40,000 to 9,000 years B.P.); Level II – elaborated in two distinct phases, firstly in the middle Holocene (6,000 to 5,000 years B.P.) and second, more recent phase, during late Holocene (3,000 to 1,000 years B.P.); Level I – formed during the late Holocene with ages obtained (>1000 years B.P.); River terraces (3,870 ± 400 years B.P. and 600 ± 30 years B.P.); And riverside terraces (ages spread throughout the Holocene). From these results, through the technique of modeling environmental systems, it was possible to establish 6 evolutionary stages of the local coastal plain, correlating them mainly to global/local Holocene climatic pulses and, in a secondary way, to other morphogenetic (AU)

• FAPESP's process: 16/21335-9 - GEOCHRONOLOGY OF SURFACE COVERAGES IN LEVELS OF LOW TERRACES IN MOUTH RIVERS UNA / PARDO (BA), RELATED OF TRANSGRESSIONS AND REGRESSIONS MARINE,ASSOCIATE WITH PULSE CLIMATE HOLOCENE
• Grantee: Vinícius Borges Moreira
• Support Opportunities: Scholarships in Brazil - Doctorate