In the Mt. Morgan district the Upper Palaeozoic sediments of the northern portion of the Yarrol Basin are exposed. By means of the several fossil horizons contained in them, the sequence has been divided into seven faunal zones ranging in age from Frasnian to late Visean. The individual formations are described, and the progressive change in their lithology from strongly felspathic to more quartzose rocks, has been used in an interpreation of the tectonic factors which controlled this sedimentation. A narrow granite batholith and associated hypabyssal material is intruded into the sedimentary formations. The whole area has been affected by two systems of normal faults; the N.E. system caused the downthrow of the northern blocks, resulting in the eastward displacement of the gently dipping northern beds. Fresh-water Mesozoic sediments were deposited unconformably on the older beds in the basin so formed.