Abstract
Mass-transport deposits (MTDs) may show a variety of deformation aspects, from poorly-deformed layers to highly deformed and homogenized deposits, as a result of the different kinds of mass-transport processes involved in their evolution. Previous studies indicate that the downslope flow transformation of MTDs is characterized by increasing disaggregation, mixing and homogenization of a non-to poorly lithified protolith, which may ultimately generate a homogenite. We here explore the role of deformation processes in the disaggregation and mixing of sediments that tend to lead to sediment homogenization and so may also control the evolution of MTDs. Using the Itararé Group of the Paraná Basin, southern Brazil as our case study, we examine several types of structures in MTDs with varying degrees of mass disaggregation and discuss the role of deformation process in the continuum homogenization of the sediment. Three deformational facies (DF-1, DF-2 and DF-3) were identified and interpreted as recording varying stages of homogenization of sediments (disaggregation and mixing) within the incipient, mature and evolved, flows respectively. These different stages show transitional aspects that indicate a continuum homogenization. The comparison between structural assemblages and the amount of matrix in the three different deformational facies indicates a close relationship between styles of deformation and the homogenization expected for mass flows. The processes that promoted disaggregation include boudinage, faulting, layer-parallel shearing and marginal deformation of intrabasinal clasts, while mixing processes that generate matrix include shearing and liquefaction/fluidization of sediments.
Original language | English |
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Article number | 104033 |
Journal | Marine and Petroleum Geology |
Volume | 112 |
Early online date | 10 Sept 2019 |
DOIs | |
Publication status | Published - 12 Feb 2020 |
Bibliographical note
This contribution is part of PhD research performed by the first author in the Postgraduate Program in Geology at UFPR (Federal University of Paraná, Brazil) with scholarship provided by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil). The study was funded by Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazil, CNPq grants 461650/2014-2 and PQ 302842/2017-9). We thank the anonymous reviewers and editor Key Ogata for constructive comments.Keywords
- Itararé group
- Paraná Basin
- Sedimentary matrix
- Submarine mass-flows
- Syn-sedimentary deformation