Scaling relationships of joint and vein arrays from The Burren, Co. Clare,Ireland

We present a study of the systematics of veins and joints in Carboniferous limestones of The Burren. Ireland. Scaling relationships were established f or fracture arrays mapped from low elevation aerial photographs that image fractures on numerous limestone pavements for areas up to ca 1 km(2). The v eins and joints occur in the same sequence. but have contrasting scaling pr operties. The veins strike north-south and cut many beds to form vertically persistent. non-stratabound arrays. They are strongly clustered and have s cale invariant geometric properties. Vein geometries suggest they grew sub- critically under relatively high differential stresses, during north-south directed Variscan compression. The joints form stratabound arrays, with reg ular spacings that scale with bed thickness. They show greater strike varia tion than the veins and have lognormal length distributions. The joints for med during uplift, under low-differential stress conditions. The contrastin g scaling properties of the joints and veins are attributed to different ov erburden stresses at the time of formation. The veins formed at greater dep ths than the joints, in conditions that favoured fracture propagation acros s mechanical discontinuities, resulting in the development of non-stratabou nd scaling properties. (C) 2001 Elsevier Science Ltd. All rights reserved.