Abstract We present the results of meso-and micro-structural analyses performed on fault-related soft-sediment deformation structures affecting poorly lithified, high-porosity siliciclastic sediments in the Crotone Basin, Southern Italy. The investigated extensional fault zone has a total displacement of ~90 m and juxtaposes marine clayish sediments in the hanging wall against arkosic to lithic arkosic sandstone in the footwall. In the footwall damage zone, deformation is achieved by a network of conjugate deformation bands, whereas the foliated fault core hosts cm-thick gouges. Deformation bands and black gouges accommodated displacement between 0.2 and 20 cm. Microstructural observations and quantitative image analysis pointed out that particulate flow operated during the early stages of faulting, followed by cataclasis after significant porosity loss. Mineralogy of clasts controlled grain-scale deformation mechanism: following this, feldspar experienced extensive intragranular crushing, while quartz grains were deformed mainly by splitting and abrasion. Permeability of pristine sandstone spans from 5.4 × 104 to 1.4 × 105 mD, while inside deformation bands is reduced by 1-2 orders of magnitude, reaching 3-4 orders of magnitude within fault gouges. Permeability drop inside the fault zone is related to the accommodated displacement along each deformation structure, potentially leading to hydraulic compartmentalization of high-porosity sandstone reservoir.

中文翻译：

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在浅埋深变形的弱岩化砂岩中变形带和凿的位移相关的微观结构和岩石物理特性（意大利克罗托内盆地）

摘要 我们介绍了对断层相关的软沉积变形结构进行的细观和微观结构分析的结果，这些变形结构影响了意大利南部克罗托内盆地的低岩化、高孔隙度硅质碎屑沉积物。所调查的伸展断层带总位移约为 90 m，上盘中的海相粘土沉积物与下盘的长石至岩屑长石砂岩并置。在下盘损伤区，变形是通过共轭变形带网络实现的，而叶状断层核心则有厘米厚的凿孔。变形带和黑色凿孔可容纳 0.2 至 20 厘米的位移。微观结构观察和定量图像分析指出，颗粒流在断层早期运行，在显着的孔隙度损失之后发生碎裂。碎屑的矿物学控制了颗粒尺度变形机制：在此之后，长石经历了广泛的粒内破碎，而石英颗粒主要通过劈裂和磨损变形。原始砂岩渗透率从5.4×104到1.4×105 mD，变形带内部减少1-2个数量级，断层泥内达到3-4个数量级。断层带内的渗透率下降与沿每个变形结构的位移有关，可能导致高孔隙度砂岩储层的水力分区。而石英颗粒的变形主要是通过劈裂和磨损。原始砂岩渗透率从5.4×104到1.4×105 mD，变形带内部减少1-2个数量级，断层泥内达到3-4个数量级。断层带内的渗透率下降与沿每个变形结构的位移有关，可能导致高孔隙度砂岩储层的水力分区。而石英晶粒的变形主要是通过劈裂和磨损。原始砂岩渗透率从5.4×104到1.4×105 mD，变形带内部减少1-2个数量级，断层泥内达到3-4个数量级。断层带内的渗透率下降与沿每个变形结构的位移有关，可能导致高孔隙度砂岩储层的水力分区。