Faults in deep marine siliciclastic rocks are often characterized by great variability in fault zone architecture and relative permeability properties. Siliciclastic rocks found in turbidite successions are commonly represented by alternating layers of various thickness and grain size, which form successions with contrasting mechanical properties. For example, the alternation of sandstone and mudstone layers is responsible for the simultaneous occurrence of brittle (cataclasis) and ductile (clay smear) deformation. In this study, we will investigate the turbidite successions outcropping in Tuscany, Italy, as the study areas contains several faults with varying values of displacement that cut through heterolithic layers. Results of field and laboratory analysis are consistent with both bed thickness and grain size distribution of alternating beds dictating the fault zone architecture in terms of fault core composition and texture, damage zone thickness, fracture intensity and height. Furthermore, presence of thin siltstone/shale layers in alternating patterns with thicker sandstone bed intervals likely enhanced the development of clay smear structures in the investigated outcrops. The analysis of deformation mechanisms and resulting fault zone architecture carried out in the selected siliciclastic rocks allow to better understand the role of inherited depositional, diagenetic, and structural heterogeneities on fault zone permeability properties.
Fault zone evolution and architecture in siliciclastic turbidites and their impact on hydraulic behaviour
Riegel, H;Volatili, T;Jablonska, D;Di Celma, C;Tondi, E
2019-01-01
Abstract
Faults in deep marine siliciclastic rocks are often characterized by great variability in fault zone architecture and relative permeability properties. Siliciclastic rocks found in turbidite successions are commonly represented by alternating layers of various thickness and grain size, which form successions with contrasting mechanical properties. For example, the alternation of sandstone and mudstone layers is responsible for the simultaneous occurrence of brittle (cataclasis) and ductile (clay smear) deformation. In this study, we will investigate the turbidite successions outcropping in Tuscany, Italy, as the study areas contains several faults with varying values of displacement that cut through heterolithic layers. Results of field and laboratory analysis are consistent with both bed thickness and grain size distribution of alternating beds dictating the fault zone architecture in terms of fault core composition and texture, damage zone thickness, fracture intensity and height. Furthermore, presence of thin siltstone/shale layers in alternating patterns with thicker sandstone bed intervals likely enhanced the development of clay smear structures in the investigated outcrops. The analysis of deformation mechanisms and resulting fault zone architecture carried out in the selected siliciclastic rocks allow to better understand the role of inherited depositional, diagenetic, and structural heterogeneities on fault zone permeability properties.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
