Abstract Two lava flows with interbedded palaeosols outcrop c. 40 km SW of Mount Kenya, near the Amboni River north of Mweiga, Kenya along the Nyeri/Thompson Falls Road, at 0°18′S; 37°48′E. These flows, overlain by loess, are principally trachyandesite and form the base of the Mount Kenya Volcanic Series which, in the early literature, is described as being of probable Miocene/Pliocene age. Here we report 39 Ar/ 40 Ar dates ( c. 5.2–5.5 Ma) and reversed magnetizations which establish a Latest Miocene to Earliest Pliocene age for these flows. Weathering characteristics of palaeosols interbedded with the lavas indicate generally dry climatic conditions during the Late Miocene, punctuated with humid events during the Pliocene and Quaternary. These Late Miocene–Quaternary palaeosols depict a relatively long and complex weathering history, followed by loess deposition. The palaeosols appear to have been episodically deflated, initially in phase with the deposition of lavas when surfaces were devoid of vegetation and later during periods of climatic deterioration when wind systems intensified. Such weathering histories within palaeosol profiles are also documented on nearby Mount Kenya, where well-weathered lower palaeosol horizons developed on Matuyama-age tills are overlain by much younger less-weathered horizons developed on Brunhes-age loess. The geochronology of Late Miocene lavas reported here provides maximum ages for weathering histories of palaeosols formed in a xeric tropical highland climate.

Abstract Glacier process models of till genesis cannot fully explain the properties of tills in Maritime Canada. A succession of local ice caps, called the Appalachian Ice Complex, developed during the last glaciation and were drained by ice streams into the submarine channels bordering the region. The migration of these centres produced areas with widely differing flow patterns, landform assemblages and deposits. Early regional phases of ice flow were characterized by wide, rapidly-flowing ice-streams that formed thick exotic, silty tills. In later phases, ice divides developed over highland areas underlain by metamorphic and igneous rocks, forming stony local tills. Terrain zones characterized by distinct transport histories and depositional sequences were produced by the interplay and migration of regional ice sheets and local ice caps. The interaction of local glaciers and previously deposited tills formed hybrid tills through two reworking processes: inheritance and overprinting. Inheritance is incorporation of till components and/or fabric into a younger till by erosion and entrainment of material from an older till. Overprinting is the injection or imprint of matrix, clasts or fabric on older tills by overriding ice. Glacial dispersal of rocks, minerals and trace elements in this complex glaciated terrain is controlled by the location of former ice divides. Simple unidirectional trains are preserved in relict terrains under divides. In ice marginal areas, reworking processes result in complex dispersal fans produced by smearing and widening of previously formed trains and fans. These dispersal fans can be modelled by vector addition of discrete flow events within each dispersal zone. A simple empirical model of glacier dispersal is presented using exponential decay and uptake algorithms, and incorporating the reworking of older till material.

Location The upper flow units of the North Mountain Basalt Forma tion extend in continuous exposure for 124 mi (200 km) along the Bay of Fundy. The massive lower unit is exposed at several places along the escarpment face of the North Mountain cuesta, and continuously along Saint Mary's Bay (Fig. 1). The five stops described here center on the remarkable exposures near Scots Bay and along the North Shore of the Minas Basin, where structuraland stratigraphic relations are well displayed. Stops are situatedon the Parrsboro and Wolfville 1:50,000-scale map sheets 21-H8and 2 i-Hi, National Topographic System, available from the Canada Map Office, 615 Booth Street, Ontario K1A 0E9. The Geology Map of The Cobequid Highlands (sheet 2), and the Geological Highway Map of Nova Scotia (Bujak and Donahoe,1980) both available from the Nova Scotia Department of Minesand Energy, Halifax, are useful for locating optional sites. Caution. The tidal range of the Bay of Fundy region attains 50 ft (15 m). Shoreline field studies are severely constrained bythe times of the tides, which vary daily. Consult the publishedcurrent tide tables or daily Halifax newspaper to plan for a dayhaving an early morning high tide. The shore should be vacatedwell before high tide to pass promontories that flood early. North Mountain and Scots Bay Syncline Stop 1 is a road cut and quarry at the base of the ridge,2.5 mi (4 km) north of Sheffield Mills on the road to Glenmont (Fig. 2). Stop 2 is on the intertidal shelf at

Location The Bay of Islands Complex forms a discontinuous north easterly trending belt of mafic-ultramafic massifs approximately 60 mi ( 100 km) long and 15 mi (25 km) wide on the west coast of Newfoundland (Fig. 1). The northernmost of the massifs, Table Mountain, lies within the Gros Morne National Park and can be reached by motor vehicle from the main Northern Penin-sula highway (Newfoundland 430) and the Bonne Bay road (Newfoundland 431). Visitors should turn left onto Newfound-land 431). Visitors should turn left onto Newfound-sures described in this guide will be found on the hills to the south of this road between a distance of 2 mi (3 km) and 6 mi ( 10 km) from the turn-off (Fig. 2). Local access is by foot since many outcrops are on the mountain top, which is, however, flat and easily traversed. Paths of easiest access to specific locations are shown in Figure 3. Park rangers are available to lead field excur sions and permits must be obtained if specimens are to be taken. Permits may be applied for by writing to Parks Canada Atlantic Regional Office, D.O.E. Historic Properties, Upper Water Street, Halifax, Nova Scotia, B3J 1S9. It is also advisable to inform Park Headquarters in Rocky Harbour if an extended stay on the moun tain is planned. This guide describes two major outcrop sections separated by a distance of approximately 2.5 mi (4 km) driving.