Trends in major ionic components of bulk precipitation were analysed for two sites, Faskally and Loch Ard forest in Scotland, for the period 1972-2000. The pattern of change was not linear. Large reductions in sulphur deposition occurred in the early 1980s and, to a lesser extent, during 1995-2000, with a period of relative stability between 1988-95. pH increased significantly at both sites but nitrate and ammonia only increased significantly at Loch Ard forest. Long-term chemical data from a total of 37 streams and lochs in four selected regions of Scotland were analysed over three time periods (all available data (mostly 1978-2000), 1988-98 and 1995-2000) to match the deposition patterns. For the whole study period a significant decline in non-marine sulphate was found at all sites while the most consistent increases in pH and alkalinity were recorded at all the high elevation loch sites in the Galloway area. Significant reductions in toxic forms of aluminium were also recorded, mostly at sites where pH had increased. Nitrate trends were equivocal except for catchments with clear-felling operations. For these sites, negative trends were found where felling occurred in the 1980s, while positive trends were found at sites with felling in the 1990s. With the exception of one site, dissolved organic carbon concentrations increased significantly with moorland sites showing smaller increases than forested sites. Associated with this change was a significant increase in complexed forms of aluminium. Trends for the 1988-98 period were much smaller than those for the whole study period and in many cases were insignificant. This contrasts with the 1995-2000 period when large and significant reductions in sulphate and nitrate were recorded along with increases in marine salts, probably as a result of climatically related events. Qualitative, experimental and monitoring data from lochs in the Galloway area revealed evidence of recovery of fish populations. Interpretation of chemical and biological trends was clearly influenced by the choice of the time series, especially in relation to deposition and climatic changes. Nevertheless, all the fresh waters included in this study are currently in the best ecological condition since the 1970s in the context of recovery from acidification.

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Note: Most sedimentary bedrock in the map area is concealed by colluvium (Qc). The main purpose of the map is to show the distribution and structure of the bedrock. Thus, only a fraction of the colluvium was mapped where it is thickest. Colors of rocks, soils, alluvium, and weathering products were selected using a Munsell Soil Color chart and the Rock-Color Chart (Goddard and others, 1948). Sedimentary rock names follow the field classification of C. M. Gilbert (as illustrated in Williams and others, 1958, p. 270) Qal Alluvium (Holocene)~Low-level deposits on floodplains and in channels that consist of gravel and sand, silt, and clay mixed in varying proportions. At edges of floodplain, grades into colluvium (Qc) and fan alluvium (Qafl). Midway Valley floodplain deposits are dark brown (7.SYR 3/2) to strong brown (7.5YR 4/6); thick to thin-bedded; lenses of fine pebbles. The channel contains basalt and limestone gravel (2-50 cm in diameter) in a matrix of coarse sand, with subordinate light-gray (N7) ash-flow tuff of Isom Formation of latest Oligocene age (1-10 percent), white chalcedony (1-2 percent), and well rounded black chert pebbles (2-3 percent). The channel in Deer Valley is small or absent; floodplain alluvium is silty clay to clayey silt, yellowish red (5YR 5/8), slightly sandy, laminated to massive, and contains lenses, 2-40 cm thick, of angular limestone pebbles and some cobbles. Floodplain alluvium of Mill Creek (southwest quarter of quadrangle) is medium gray (N5), sandy and clayey silt to silty clay; thin interbeds of pebbles (limestone, basalt and sandstone); is terraced behind old beaver dams in places. Base covered; estimated thickness 2-5 m Qaf 1 AIIuvial-fan deposits (Holocene)~Fans around Navajo Lake: upper fan, chiefly clast-supported coarse gravel of limestone and minor sandstone and conglomerate containing some sandy matrix; middle to lower fan, pebbly sand to sandy pebble gravel, angular fine limestone pebbles, scarce small cobbles (8 cm in diameter); reddish yellow (5YR 6/6), poorly sorted, loamy quartz fine sand; distal fan is silty, slightly pebbly and clayey, very fine to coarse quartz and limestone sand, crudely stratified. Some hard layers 10-20 cm thick are cemented by calcium carbonate. East of dam, alluvium interfingers and grades to lake sediment (Qla) toward axis of valley; along shore it interfingers and grades to lake gravel (Qlg). At west end of Midway Valley, scarce ash-flow tuff (Isom Formation) gravel 20-80 cm in diameter occurs in moderate brown (5YR 4/4), silty fine sand matrix. On and south of plateau escarpment (Pink Cliffs), alluvium is dark-yellowish-brown (10YR 4/4) sand, silt, poorly to moderately well-sorted sand, pebbly sand, and silt, intermixed and interbedded. Thickness estimated to be 5-7 m at mid-fan Qat1 Alluvial-terrace deposits (Holocene)-In Midway Valley, sandy, poorly sorted, resistant gravel of basalt, ash-flow tuff of the Isom Formation, chalcedony, and sparse, round, chert and quartzite pebbles. Top of terrace is 1-2 m above stream channel. On Mill...

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