--> Tectonostratigraphic modelling of sedimentary units overlying the Volcano-sedimentary Complex based in Landsat Imagery and altimetry data (Iberian Pyrite Belt, Portugal)

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Tectonostratigraphic modelling of sedimentary units overlying the Volcano-sedimentary Complex based in Landsat Imagery and altimetry data (Iberian Pyrite Belt, Portugal)

Abstract

This work refers to the tectonostratigraphic modelling of the sedimentary units overlying the Volcano-sedimentary Complex, and usually refered as Paraíso Formation (Iberian Pyrite Belt, South Portuguese Zone). This unit is represented by interstratified fine sandstones and black shales, and it was dated from late Famennian to early Visean based on its fauna and microfauna.

The work was carried out using the interpretation of satellite images and other data, namely Landsat 8, and altimetry data from the topographic map (1:25 000).

Landsat imagery, through spectral transformations methods (correlation coefficient, band ratio, principal component analysis), allowed the creation of RGB composite images based on Short Wave Infrared (SWIR), Near Infrared (NIR) and Red bands. Those images were filtered and treated by using the spectral signature of distinctive elements of the fracture zones. Through visual interpretation of those images, it was created three directional filters (N-S, NW-SE and NE-SW) corresponding to the direction of the structures represented in the Geological Map of Portugal (1:500 000). Moreover, it was possible to delimitate the main alignments of the study area, within the raster resolution, based on the visual interpretation of discontinuities between surface features. In rugged areas, the altimetry data enabled the determination of direction of the structural accidents, based on the analysis of slopes.

The obtained alignments were then correlated with available wells data. From the relation between strike and dip, it was possible to check the typology of each alignment. Their geostatistic analysis has enabled to classify those alignments into several families of different ages, as well as the determination of paleostress fields. Both data were integrated with paleogeographical data, which have allowed the creation of a palinspatic model representing the geodynamic constraints that have affected the studied geological units.

Taken the approximate thickness of the Paraíso Formation into account, the proposed tectonostratigraphic modelling can be a useful tool to ground both maturation models and hydraulic fracturing models, as this formation shows some potential for unconventional hydrocarbon resources exploration.