The temporal relationship between joints and faults

Examples are presented of three temporal relationships between joints and f aults: joints that pre-date Faults. joints that are precursors to, or synch ronous with, faults: and joints that post-date faults. Emphasis is placed o n strike-slip faults in carbonate beds, but other examples are used. Genera l rules are given for identifying the thr rr temporal relationships between joints and faults. Joints that formed before faults can be dilated, sheare d or affected by pressure solution during faulting, depending on their orie ntation in relation to the applied stress system. Faulted joints can preser ve come original geometry of a joint pattern. with pinnate joints or veins commonly developing where faulted joints interact, Joints formed synchronou sly with faults reflect the same stress system that caused the faulting, an d tend to increase in frequency toward faults. In contrast, joints that pre - or post-date faults tend not to increase in frequency towards the fault. Joints that pout-date a fault may cut across or. abut the Fault and fault-r elated veins, without bring displaced by the fault. They may also lack dila tion near the fault, even if the fault has associated veins. Joints formed either syn- or post-faulting may curve into the fault. indicating stress pe rturbation around the fault. Different joint patterns may exist across the fault because of mechanical variations. Geomrtric features map therefore be used in the field to identify the temporal relationships between faults an d joints, especially where early joints affect or control fault development , or where the distribution of late joints an influenced by faults. (C) 200 1 Elsevier Science Ltd. All rights reserved.