Illite crystallinity data from the Lesser Himalaya of Garhwal show that the upper Paleocene-lower Eocene Subathu Formation, deposited immediately prior to or early in the Himalayan collision, has not suffered significant regional metamorphism. The regional metamorphism in the upper Precambrian–lower Palaeozoic Lesser Himalaya must therefore be precollisional. Illite crystallinity results from Lesser Himalayan fossiliferous Permian strata show grades of metamorphism intermediate between upper Paleocene–lower Eocene and Proterozoic–lower Palaeozoic strata indicating a pre-Permian regional metamorphism for the latter.

K–Ar whole rock cooling ages provide supporting evidence for pre-collisional regional metamorphism in the Lesser Himalaya. Slates and phyllites below the Main Central Thrust (MCT) show pre-Cenozoic whole rock ages, as old as Ordovician (486 Ma). Whilst resetting of K–Ar whole rock ages has occurred locally in pervasively cleaved Palaeozoic strata (near thrusts?), fracture cleaved Permian and upper Paleocene–lower Eocene sediments give whole rock ages compatible with diagenesis. The illite crystallinity results confirm that these sediments have not been heated above mica blocking temperatures.

Muscovite 40Ar–39Ar and K–Ar mineral ages within the 5 km thick MCT zone are as young as 8 Ma indicating that temperatures of above ~ 350°C were maintained in the MCT zone for over 10 Ma after high temperature (~ 550°C) shearing on the MCT. This heating did not affect the MCT footwall Lesser Himalaya to any regional extent, where pre-Permian low grade regional metamorphism has not been overprinted.

Meta-sediments in the Larsemann Hills that preserve a coherent stratigraphy, form a cover sequence deposited upon basement of mafic–felsic granulite. Their outcrop pattern defines a 10 kilometre wide east–west trending synclinal trough structure in which basement–cover contacts differ in the north and the south, suggesting tectonic interleaving during a prograde, D1 thickening event. Subsequent conditions reached low-medium pressure granulite grade, and structures can be divided into two groups, D2 and D3, each defined by a unique lineation direction and shear sense. D2 structures which are associated with the dominant gneissic foliation in much of the Larsemann Hills, contain a moderately east-plunging lineation indicative of west-directed thrusting. D2 comprises a colinear fold sequence that evolved from early intrafolial folds to late upright folds. D3 structures are associated with a high-strain zone, to the south of the Larsemann Hills, where S3 is the dominant gneissic layering and folds sequences resemble D2 folding. Outside the D3 high-strain zone occurs a low-strain D3 window, preserving low-strain D3 structures (minor shear bands and upright folds) that partly re-orient D2 structures. All structures are truncated by a series of planar pegmatites and parallel D4 mylonite zones, recording extensional dextral displacements.

D2 assemblages include coexisting garnet–orthopyroxene pairs recording peak conditions of ∼ 7 kbar and ∼ 780°C. Subsequent retrograde decompression textures partly evolved during both D2 and D3 when conditions of ∼ 4–5 kbar and ∼ 750°C were attained. This is followed by D4 shear zones which formed around 3 kbar and ∼ 550°C.

It is tempting to combine D2–4 structures in one tectonic cycle involving prograde thrusting and thickening followed by retrograde extension and uplift. The available geochronological data, however, present a number of interpretations. For example, D2 was possibly associated with a clockwise P–T path at medium pressures around ∼ 1000 Ma, by correlation with similar structures developed in the Rauer Group, whilst D3 and D4 events occurred in response to extension and heating at low pressures at ∼ 550 Ma, associated with the emplacement of numerous granitoid bodies. Thus, decompression textures typical for the Larsemann Hills granulites maybe the combined effect of two separate events.

The westward continuation of the Highland Border fault of Scotland (HBFZ) into Ireland is problematic. It is widely thought to follow a pronounced magnetic and gravity lineament, the Fair Head-Clew Bay Line (FCL). The advantage of this interpretation is that it places all the Ordovician ophiolitic complexes and associated sedimentary basins to the south of the FCL, which would represent the contact between Laurentia and the outboard terranes. Its main shortcomings are that both the deep structure and timing of strike-slip are different on the HBFZ and FCL. In Ireland the FCL is a north-dipping feature that can be traced to the Moho on BIRPS profiles, while the HBFZ has no such signature. Terrane amalgamation in western Ireland was completed by the late Ordovician, while in Scotland the Midland Valley terrane did not finally dock until the early Devonian. These considerations suggest that in western Ireland a branch of the HBFZ exists, which was active in post-Ordovician time and must lie south of Connemara. An examination of Irish geological, geophysical and image-processed magnetic data shows that a profound lineament can be traced from Antrim to Galway Bay (the Antrim–Galway Line). Stitching plutons date movement on it as pre-405 Ma. We propose that the Antrim–Galway Line represents the continuation of the Scottish HBFZ, while the FCL is a preserved Ordovician splay of the HBFZ system whose northdipping geometry is a product of Ordovician collapse of the orogen in western Ireland.

A new lithostratigraphy is presented for the Skiddaw Group (lower Ordovician) of the English Lake District. Two stratigraphical belts are described. Five formations are defined in the Northern Fells Belt, ranging in age from Tremadoc to early Llanvirn. They are all mudstone or sandstone dominated, of turbidite origin; in ascending order they are named the Bitter Beck, Watch Hill, Hope Beck, Loweswater and Kirk Stile formations. Two formations are defined in the Central Fells Belt, ranging in age from late Arenig to Llanvirn. These are the Buttermere Formation – a major olistostrome deposit – overlain by the Tarn Moor Formation, consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds. A revised graptolite and new acritarch biostratigraphy for the Skiddaw Group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub-assemblages. The provenance of the group is assessed from detailed petrographical and geochemical work. This suggests derivation, in the early Ordovician, largely from an old inactive continental arc terrane lying to the southeast, with the appearance of juvenile volcanic material in the Llanvirn. Comparisons and correlations of the Skiddaw Group are made with the Isle of Man and eastern Ireland.

The type specimen of Regnosaurus northamptoni Mantell, a partial right mandible, is redescribed and compared with a wide variety of dinosaurian taxa. We suggest that Regnosaurusis not an ankylosaur or a sauropod as previously thought, but represents the fragmentary remains of a ‘primitive’ stegosaur. Regnosaurus and Huayangosaurus share two derived characters, suggesting that these two genera should be provisionally regarded as sister taxa. The implications of these findings for stegosaur evolution and biogeography are discussed briefly.

The Fenland basin is filled with unconsolidated Holocene marine and freshwater deposits. Stratigraphic studies of the basin date back to 1877. This paper reviews the various lithostratigraphic schemes which have been proposed. Particular attention is paid to the presently accepted lithostratigraphy. Examples and a case study of a newly surveyed area are used to highlight its failings. Many of the difficulties experienced in Fenland are common to problems of lithostratigraphic classification in coastal lowland environments, as is demonstrated by reference to recent debate in the southeastern North Sea. In Fenland, as a result of the shortcomings of the various schemes, it is proposed that a new lithostratigraphy with formal stratotypes is devised. Suggestions are made as to the form this new stratigraphy could take. In the meantime, an informal lithostratigraphy should be adopted which has no regional or chronostratigraphic connotations.