Microfossil (pollen and diatom) evidence is presented from sites in the Forth valley, south-central Scotland, where alternating organic and estuarine minerogenic deposits record the influence of the changing Holocene sea level. Radiocarbon dating confirms the age of the Main and Low Buried Beaches, and of the Main Postglacial Transgression, in different parts of the Forth valley. Radiocarbon dates on shells from beds in the carse sediment and a Mesolithic shell midden near Grangemouth relate to the falling sea level in the 4th and 5th millennia BP. Sea-level curves are constructed for the western and eastern Forth valley.

Carboniferous sandstones from within the thermal aureoles of igneous intrusions in the Midland Valley of Scotland sometimes have a strong, black colour and are termed ‘black sandstones’. Tait (1926) concluded that the black sandstones are the products of the thermal metamorphism of petroliferous sandstones, a theory which is discussed here in the light of modern petrological and geochemical techniques.

The black colour of the sandstones is due to an amorphous, opaque bitumen which usually coats illitic clays, fills porosity and was mostly emplaced at a fairly late diagenetic stage. This solid bitumen has a low reflectance (c. 0·15% R0), no fluorescence under blue-light excitation, is insoluble in organic solvents, is isotopically heavy and has a very low H/C atomic ratio. These data, together with the field relationships of the black sandstones and igneous intrusions, suggest that the bitumen was formed by the thermal alteration of hydrocarbons, as described by Tait (1926), rather than by other possible mechanisms such as the deasphalting of an oil, or the generation of hydrocarbons from organic-rich rocks heated by igneous intrusions, followed by fractionation during migration. This conclusion suggests that by the time of emplacement of the quartz-dolerite intrusions, and some of the alkali-dolerite sills, there had been widespread generation and migration of hydrocarbons which possibly could have been preserved to the present day where not thermally altered.

Mass balance equations are derived which link the ratios Ts/ (suspended load/dissolved load from chemical weathering) and Tb/Ts (bed load/suspended load), with any two geochemical components present in the source rock and the alluvial system. If the dissolved load is unknown the ratios can be estimated from the relatively insoluble silica and alumina. The ratio Ts/, which for large river basins depends on climate and relief, can thus potentially be determined from ancient alluvial sequences.

The equations help define the source composition of a group of 13 modern rivers for which Ts, and alluvial geochemistry are known. These rivers together drain 27% of the continental surface. For a source area with the average continental sandstone to shale ratio of 0·6 the observed average value of Ts/ is obtained when limestone, sandstone and shale are present in the proportions 6·7:21·6:35·7. The figure of 64% sediment in the source area is very similar to the 66% determined by Blatt and Jones (1975) from geological maps of the continents. The equations also show that average bed load transport rate into these 13 basins is about 27% of total transport, and into the Amazon basin about 37%. Bed load transport rates out of the basins, into the sea, are relatively very small.

In the Southern Uplands of Scotland, the youngest greywackes along the SE margin of the Northern Belt are shown to be of Ashgill age. Mudstones interbedded with the dominantly quartzose greywackes of the Shinnel Formation have yielded Dicellograptus anceps, indicating the anceps Biozone. In addition, the newly-defined mafic-rich Glenlee Formation, lying to the SE of the Shinnel Formation in the New Galloway-Moniaive area, has yielded fossils of the pacificus Subzone, the upper subzone of the anceps Biozone. Since the oldest greywackes of the Central Belt, separated from the Northern Belt by the Orlock Bridge Fault, are now confirmed as of basal Silurian acuminatus Biozone age, the stratigraphical break across the Orlock Bridge Fault is greatly reduced, lending support to the ‘single terrane’ model for the Southern Uplands.