Using a combination of optical microscopy and X-ray texture goniometry, an integrated microstructural and crystallographic fabric study has been made of quartz mylonites from thrust sheets located beneath, but immediately adjacent to, the Moine thrust in the Assynt and Eriboll regions of NW Scotland. A correlation is established between shape fabric symmetry and pattern of crystallographic preferred orientation, a particularly clear relationship being observed between shape fabric variation and quartz a-axis fabrics.

Coaxial strain paths dominate the internal parts of the thrust sheets and are indicated by quartz c- and a-axis fabrics which are symmetrical with respect to foliation and lineation. Non-coaxial strain paths are indicated within the more intensely deformed quartzites located near the boundaries of the sheets by asymmetrical c- and a-axis fabrics. These kinematic interpretations are supported by microstructural studies. At the Stack of Glencoul in the northern part of the Assynt region, the transition zone between these kinematic (strain path) domains is located at approximately 20 cm beneath the Moine thrust and is marked by a progression from symmetrical cross-girdle c-axis fabrics (30cm beneath the thrust), through asymmetrical cross-girdle c-axis fabrics to asymmetrical single girdle c-axis fabrics (0·5 cm beneath the thrust).

Tectonic models (incorporating processes such as extensional flow, gravity spreading and tectonic loading) which may account for the presence of strain path domains within the thrust sheets are considered, and their compatibility with local thrust sheet geometries assessed.

A stem-base of Oxroadia gracilis is described showing 12 distal rhizophores and 72 roots. The rhizophores branch in a manner interpreted as dichotomy in successive planes at right angles. Each has a siphonostele which may possess medullary tracheids. Root-traces are monarch and wedge-shaped in section and their departure leaves ramular gaps in the siphonostele. The largest root may have functioned as a tap-root formed earlier than the rhizophores and exogenous. Only two out of ten known rooting specimens show rhizophores.

An aerial stem with leaves shows secondary xylem up to the level of the probable second dichotomies.

Leaves have slightly decurrent clasping bases forming low cushions and are recurved. Ligules (when preserved) occur in deep cavities of leaf-bases. In the apical region young leaves are small, recurved, and grooved distally below, giving a pseudo-forked appearance in cross sections of the stem.

Only incomplete strobili are known.

Comparisons are made with ‘Lepidodendron’ saalfeldense Solms-Laubach, and Trabicaulis ftabellilignis Meyer-Berthaud; these are considered co-generic.

Oxroadia is recorded from the Oil-Shale Group (late Viséan or Asbian) near Kinghorn, Fife, Scotland; and from the Cementstone Group (late Tournaisian or Courceyan) East Lothian, Scotland; Berwickshire, Scotland; and Northumberland, northern England.

Detailed mapping, stratigraphic logging and structural analysis of the Hawasina Window culmination in the central Oman Mountains of Arabia reveals an extremely complex thrust geometry and structural history. The initial thrust sequence involved a southwestward propagating stacking during telescoping of the Arabian continental margin slope (Sumeini complex), and time-equivalent, more distal Tethyan basin (Hawasina and Haybi complexes) facies rocks. The Semail thrust, carrying the 12 km-thick ophiolite sequence, progressively overlaps Haybi and Hawasina duplexes towards the SW. Late stage “leap-frog” thrusts have punched Sumeini duplexes higher up into the earlier thrust stack locally reversing the normal stacking order. SW-directed thrusts and SW-facing folds in the SW and NE-directed backthrusts and NE-facing backfolds in the NE have created a fan structure cored by the Jebel Rais “pop-up” composed of Sumeini slope facies rocks.

The palaeogeographic presence of a large NE-facing promontory in the Cretaceous shelf edge is inferred beneath the Window. The frontal ramp of this promontory was sufficiently large to inhibit the overthrusting of large volumes of Hawasina and Haybi complex rocks. The whole central part of the Window shows NE-facing and verging backfolds and backthrusts affecting all duplexes from the lowest Sumeini up to the Semail ophiolite. The promontory is bounded by major lateral ramps to the NW (Wadi Shafan area) and SE (Jebel Milh area). A map and four balanced cross-sections are presented here to promote a complex model for the structural evolution of the Hawasina Window.

Four tiny obvious larvae unassignable to larger “Orsten” arthropods are described and reconstructed. Two of them have a naupliar appearance and may belong to crustaceans, whereas the other two represent as yet unknown types of euarthropodan larvae.