The Upper Old Red Sandstone in the south west Scottish Borders was deposited as a fluviatile sequence in an interior alluvial basin named the Border Basin. High and low sinuosity streamu deposited sandstones and pebbly sandstones as point bars and channel bars. Thick flood deposits accumulated in persistent floodbasins. The streams flowed from the south west and brought in detritus from sourcelands in Galloway. A coarsening-up trend within the Upper O. R. S. may have resulted from increased stream gradients caused by gradual isostatic uplift in the hinterlands. The overlying Tournaisian sediments in the Langholm and Newcastle areas were deposited in the newly formed and subsiding Northumberland Basin. The Whita fluvio-deltaic system, draining the southern Uplands to the north, dominated sedimentation during the early part of the Tournaisian. Interior and marginal (coastal plain) fluviatile facies occur in the Langholm area and deltaic facies occur in the Bewcastle area. In the upper Tournaisian the Bcwcastle deltaic system, flowing from the north east, was dominant. In both delta systems periods of delta advance, during which pro-delta, delta front and on-delta facies were deposited, were followed by delta abandonment, slow subsidence and gulf carbonate sedimentation. Carbonate sedimentation included stromatolite and serpulid growth and formation of a range of marginal and offshore marine facies. Objective carbonate facies divisions are made using Q-mode cluster analysis. Tournaisian stromatolites are composed of detrital/micrite laminae formed by filamentous blue-green algae and calcareous algal filament laminae formed by encrusting Codiacean algae. biostromes with dome, blister, polygonal, pillar and club growth forms grew in shallow subtidal through to intertidal environments. Biostromes with blister, cusp and crinkle growth forms grew in high intertidal and supratidal environments with gypsum crystals and non-ferroan dolomites forming in the shallow subsurface. Bioherms and oncolitcs grew in sheltered subtidal and agitated shoal water environments respectively. Serpulid biofacies occur as autochthonous biostromes, bioherms and a single reef. Thu Birrenswark Lavas, which separate the radically different Upper O. R. S. and Tournaisian palaeogeographies, provide the key to the initiation and origin of the Northumberland Basin. These bazalts show evidence of fissure eruption and probably formed by partial melting of the upper mantle along the northern basin margin. Partial melting caused upwarp, tensional stress and basin subsidence by normal faulting. Substidence established a southerly in the central Southern Upland: and enabled the plantaion of the Southern Uplands by the Lower Visean.