The first section of the paper is concerned with a detailed account of the structure of the classic Schiehallion area. The account is extended to the flat belt via the Glen Lyon-Ben Lawers area. It is demonstrated that major D1 folds involve the whole of the Appin and Argyll groups and now face SE. However, the original D1 folds were probably open upward-facing folds which have been refolded and modified by the dominant D2 deformation. D2 is represented by an antiformal complex which culminates downwards in the Boundary Slide, a zone of strong deformation associated with NW translation of Dalradian over the ‘young Moine’ rocks. D3 has been responsible for the rotation of the originally flat D2 structures into their present ‘steep’ attitudes N of Glen Lyon. D4 is represented by the strike-swing of the lower Dalradian formations, possibly related to early movements on the two major faults that bound the area. The concept of a D1 Tay Nappe which roots in the ‘young Moine’ to the N is retained, although the scale and flat attitude of that fold is regarded as in part a product of D2.

The Topsails igneous terrane of western Newfoundland contains several intrusive and volcanic suites underlain and separated by screens of older intrusive rocks. The heterogeneous Hungry Mountain complex yielded U-Pb zircon upper and lower intercept ages of 2090 ± 75 Ma and 467 ± 8 Ma, demonstrating a significant inherited component of Aphebian age, while an adjacent suite of relatively massive granodioritic to granitic rocks yielded a slightly discordant U-Pb zircon age of 460 ± 10 Ma. The 438 ± 8 Ma age of the Rainy Lake complex, a suite of island arc type intrusive rocks, suggests it forms part of a Silurian magmatic episode, which also included Springdale Group bimodal volcanics (429 ± 4 Ma), and peralkaline granite and subvolcanic porphyries which intrude the Springdale Group (429 ± 3 Ma and 427 ±3 Ma, respectively). Most igneous units contain a slight component of inherited zircon, but initial 87Sr/86Sr ratios (average 0·704) are similar to calculated ‘Bulk Earth’ values at this time.

Available data suggest that the Topsails terrane formed an oceanic tract with active volcanic island arcs when obduction commenced in early Ordovician time. The subsequent magmatic history, including the major but short-lived early Silurian magmatism, can be directly or indirectly related to obduction processes, including over-riding of the Topsails terrane by ophiolitic allochthons. There is no evidence of any Acadian (Devonian) igneous activity in the Topsails terrane.

The Dinantian Lower Oil-Shale Group of the Edinburgh area records the evolution of a SW–NE trending basin within an area of fluvial-dominated deltaic sedimentation, with rare marine incursions from the E. The sequence at Granton records the abandonment of a delta lobe, with deltaic sandstones overlain by lagoonal mud-shales. These thinly-laminated non-bioturbated mud-shales record low-energy, stagnant conditions. Fish, ostracodes and conchostracans inhabited the lagoon at this time.

Within the mud-shale sequence is the dolomitic Granton “shrimp-bed” which contains fenestrae, possible gypsum pseudomorphs and in situ shrinkage breccias suggesting periods of emergence. The “shrimp-bed” contains a number of laminae packed with soft-bodied fossils including marine forms, which resulted from brief marine incursions into the stagnant lagoon. The fluctuating salinity conditions seem to have favoured the development of an unusual fauna of shrimp-like crustaceans, fish, conchostracans, ostracodes and bellerophontid gastropods. This fauna appears to have suffered periodic mass mortalities during marine incursions which brought orthocone cephalopods, polychaete worms and conodonts into the lagoon, according to our current knowledge of the distribution of these marine taxa in the sequence.

The Granton sequence displays a variety of ductile and brittle deformation features most of which can be attributed to local SW-directed extension related to regional dextral strike-slip across the Midland Valley of Scotland.

A zircon age of 429 + 6, −5 Ma on felsic volcanic rocks of the Springdale Group, a sequence of bimodal volcanic rocks and redbeds, establishes a Llandovery age for this group. Similar sequences from other parts of the Dunnage and Humber zones of Newfoundland also give Llandovery fossil or radiometric ages, demonstrating temporal correlation among lithologically similar sequences in these zones.

Distinctive sequences of bimodal, subaerial rhyolite and basalt with associated subaerial to shallow marine sedimentary rocks within the Avalon and Meguma zones of Nova Scotia give fossil or radiometric ages demonstrably or arguably very close to the age of the Springdale Group. These sequences suggest an overlap assemblage fixing the minimum age of accretion of the Avalon and Meguma zones to North America. The age and the magmatic and sedimentary character of the assemblage are compatible with origin on or from continental crust, implying that the Iapetus ocean was closed prior to Early Silurian time. If these considerations are correct, the Devonian Acadian orogeny must involve either thermal and mechanical readjustments subsequent to the closing of the Iapetus ocean, or a completely separate episode of plate motion.

Deposits of windblown sand up to 4 m thick on the Torridon Sandstone massif of An Teallach are shown to be of predominantly niveo-aeolian origin, a form of sedimentation hitherto unrecognised in upland Britain. Sand grains weathered from bedrock and from exposed clasts on plateau areas are blown on to the winter snowpack on surrounding slopes. When the snow melts, the grains are lowered on to the underlying vegetation, which traps the sand and thus allows a stable deposit to accumulate. The deposits formed in this way are massive, poorly sorted and coarser than most aeolian deposits, comprising mainly medium sand (212–600μm) with a substantial proportion of coarse sand and even very small pebbles. The coarseness and poor sorting of the sands reflect the size of grains available for transportation, the strength of the wind, short transport distances and admixture of different grades of sand during deposition. Sand accumulation began in the Early Flandrian before c. 7900 BP, but was eventually much reduced by the establishment of vegetation cover over the plateau source area. Recent disruption of this vegetation cover triggered either by increased storminess or overgrazing resulted in extensive erosion of sand deposits on the plateau and their redeposition on surrounding slopes. Niveo-aeolian deposition continues on lee slopes at present, but is offset by erosion of unvegetated scarps at the margins of the deposits.