Abstract
Abstract. Joint systems in the eastern portion of the Ebro Basin of the eastern Pyrenees enjoy near continuous exposure from the frontal portion of the belt up to the external portion of its associated foredeep. Utilizing orthophoto mosaics of these world-class exposures, we have manually digitized over 30 000 joints within a 16 km×50 km study area. The mapped traces exhibit orientations that are dominantly perpendicular to the trend of the belt (transverse) and, subordinately, parallel to the belt (longitudinal). In particular, joints systematically orient perpendicular to the trend of the belt both in the frontal folds and in the inner and central portion of the foredeep basin. Longitudinal joints occur rarely with a disordered spatial distribution, exhibiting null difference in abundance between the belt and the foredeep. Joint orientations in the external portion of the foredeep become less clustered, with adjacent areas dominated by either transverse or oblique joints. Our data indicate that joints in the studied area formed in the foredeep in response to a foredeep-parallel stretching, which becomes progressively less intense within the external portion of the foredeep. There, the minimum stress direction becomes more variable, providing evidence of the poor contribution of the forebulge-perpendicular stretching on stress organization.
Highlights
IntroductionFractures can be effective pathways for fluid flow (e.g., Laubach et al, 2019), impacting the production of hydrocarbons (Barr et al, 2007; Engelder et al, 2009; Questiaux et al, 2010) and geothermal water (Haffen et al, 2013; Vidal et al, 2017), the pathways and fates of contaminants released from deep geological radioactive waste repositories (Berkowitz et al, 1988; Iding and Ringrose, 2010), and the sustainable management of groundwater (Masciopinto and Palmiotta, 2013)
Both Mesh 1 and Mesh 2 have Rπ > 0.5 across almost the entire study area, with the only exception being in its NW corner
In the central portion of the study area, the difference between Rπ and Rπ/2 is less pronounced in Mesh 1 than Mesh 2
Summary
Fractures can be effective pathways for fluid flow (e.g., Laubach et al, 2019), impacting the production of hydrocarbons (Barr et al, 2007; Engelder et al, 2009; Questiaux et al, 2010) and geothermal water (Haffen et al, 2013; Vidal et al, 2017), the pathways and fates of contaminants released from deep geological radioactive waste repositories (Berkowitz et al, 1988; Iding and Ringrose, 2010), and the sustainable management of groundwater (Masciopinto and Palmiotta, 2013). Layer bending and stretching during the growth of thrust-related anticlines have conventionally been invoked as the principal causative process for the development of joints oriented approximately parallel (e.g., Ramsay, 1967; Murray, 1968) and perpendicular (e.g., Dietrich, 1989; Lemiszki et al, 1994) to the trend of the belt and of the thrust-related anticlines. S. Tavani et al.: Transverse jointing in foreland fold-and-thrust belts ing and thrusting within the foreland region (e.g., Doglioni, 1995; Zhao and Jacobi, 1997; Tavarnelli and Peacock, 1999; Lash and Engelder, 2007; Branellec et al, 2015; Basa et al, 2019; Giuffrida et al, 2019; Martinelli et al, 2019; Carrillo et al, 2020), where joints are layer-perpendicular and commonly oriented parallel (longitudinal) and perpendicular (transverse) to the belt–foredeep–forebulge trend (Tavani et al, 2015)
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