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The history of alluvial fan and terrace formation within a stretch of the Ouarzazate basin along the southern margin of the Central High Atlas is reconstructed using geomorphological and [sup.10]Be terrestrial cosmogenic nuclide (TCN) methods. Alluvial fan and terrace incision was controlled partially by a drop in base level during the Pliocene or early Pleistocene as the outlet channel, the Draa river, progressively cut through the Anti-Atlas to the south of the Ouarzazate foreland basin, the drainage of which started to become external after a long period of internal drained conditions. The alluvial fans and terrace surfaces have abandonment ages that date to at least the past four glacial cycles. Their formation was strongly modulated by climate on glacial--interglacial time scales as base level dropped. This demonstrates a strong climatic control on sediment transfer and landscape denudation during the Quaternary and provides a model for understanding sediment transfer in other intracontinental mountain belts. Furthermore, these data show that mean rates of fluvial incision in this region range between 0.3 and 1.0 mm [a.sup.-1] for the latter part of the Quaternary. This study provides the first comprehensive TCN chronology for the Atlas Mountains, and it illustrates the applicability and limitations of TCN methods.

Large fans and terraces are frequent in the Khumbu Himal within the high Himalayan valleys south of Mt. Everest. These features are composed of massive matrix- and clast-supported diamicts that were formed from both hyperconcentrated flows and coarse-grained debris flows. Cosmogenic radionuclide (CRN) exposure ages for boulders on fans and terraces indicate that periods of fan and terrace formation occurred at c. 16, c. 12, c. 8, c. 4 and c. 1.5 ka, and are broadly coincident with the timing of glaciation in the region. The dating precision is insufficient to resolve whether the surfaces formed before, during or after the correlated glacial advance. However, the sedimentology, and morphostratigraphic and geomorphological relationships suggest that fan and terrace sedimentation in this part of the Himalaya primarily occurs during glacier retreat and is thus paraglacial in origin. Furthermore, modern glacial-lake outburst floods and their associated deposits are common in the Khumbu Himal as the result of glacial retreat during historical times. We therefore suggest that Late Quaternary and Holocene fan and terrace formation and sediment transfer are probably linked to temporal changes in discharge and sediment load caused by glacier oscillations responding to climate change. The timing of major sedimentation events in this region can be correlated with fans and terraces in other parts of the Himalaya, suggesting that major sedimentation throughout the Himalaya is synchronous and tied to regional climatic oscillations. Bedrock incision rates calculated from strath terrace ages average c. 3.9 mm [a.sup.-1], suggesting that the overall rate of incision is set by regional uplift.

The Barkol Tagh and Karlik Tagh ranges of the easternmost Tien Shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range. Barkol and Karlik Tagh and lesser ranges to the north are bounded by active thrust faults that locally deform Quaternary sediments. Major thrusts in Karlik Tagh connect along strike to the east with the left-lateral Gobi-Tien Shan Fault System in SW Mongolia. From a Mongolian perspective, Karlik Tagh represents a large restraining bend for this regional strike-slip fault system, and the entire system of thrusts and strike-slip faults in the Karlik Tagh region defines a horsetail splay fault geometry. Regionally, there appears to be a kinematic transition from thrust-dominated deformation in the central Tien Shan to left-lateral transpressional deformation in the easternmost Tien Shah. This transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the NNE-directed maximum horizontal stress in the region and the pre-existing basement structural grain, which is northwesterly in the central Tien Shan (orthogonal to [SH.sub.max]) but more east-west in the eastern Tien Shan (acute angular relationship with [SH.sub.max]). Ar-Ar ages indicate that major range-bounding thrusts in Barkol and Karlik Tagh are latest Permian-Triassic ductile thrust zones that underwent brittle reactivation in the Late Cenozoic. It is estimated that the modern mountain ranges of the extreme easternmost Tien Shah could have been constructed by only 10-15 km of Late Cenozoic horizontal shortening. Keywords: Tien Shan, Cenozoic, tectonics, intracontinental belts.

Bedrock and Quaternary alluvial fans in the forelands of the northern Gobi Altai have been faulted and warped by foreland-propagating thrust faults to form elongate hills known as forebergs. Forebergs near Bogd town, north of Arsta Bogd, and at Ih Hetsuu, north of Baga Bogd were mapped and their formation constrained using luminescence dating of lacustrine and fanglomerates sediments to give localized uplift rates of c. 0.05 m [ka.sup.-1], and between c. 1.6 and 4.1 m [ka.sup.-1], respectively. Comparisons between vertical surface rupture during the 1957 Gobi Altai earthquake with the age and amount of uplift of lacustrine sediments provide a tentative estimate of between 1288 [+ or -] 382 to 497 [+ or -] 120 years for the average recurrence interval of great earthquakes in the Baga Bogd region. These localized uplifts rates support the view that the Gobi Altai Mountains probably took between 50 and 25 million years to form and were, therefore. coeval with the uplift of the Himalayas and the Tibetan Plateau. Keywords: Gobi Altai, Mongolia, earthquakes, luminescence dating, uplift rates.