Surveys of emergent terraces and U-series ages for ten sites along the coast of East Timor provide estimates of late Quaternary differential vertical strain in the most mature region of the Banda Arc-continent collision complex. Over a distance of ~180 km vertical displacement rates vary between 0.0 and 1.6 meters per 1000 years for the last 150,000 years. Two models of terrace formation (constructional and erosional) are applied to interpret terrace ages from coral ages and to estimate uplift rates. The highest uplift rates are from three sites over a distance of 15 km along the coast. Uplift rates were estimated from corals approximately 20 m above mean sea-level that yield ages of c. 54–74 ka, which correspond to the 3a (c. 49-52 ka) sea-level highstand and a possible highstand or standstill in regression between the 5a sea-level highstand and the 4 sea-level lowstand . These ten sites and resulting variable uplift rates are used constrain a wavelength of deformation due to the fact that recognizable terraces along the coast are not consistent. Terraces cannot be correlated over distances greater than 10 km, vary between 2 to 25 in number, and reach varying altitudes between ~100 and 600 meters above sea-level. The results propose that along an east-west transect a background surface uplift rate increases from 0.1 meter per 1000 years near Subau to 0.5–0.6 meters per 1000 years west of Baucau and remains at that rate for over 170 km. This would indicate a broad wavelength of deformation, possibly related to lithospheric scaled processes. However, superimposed on this background uplift rate is a shorter wavelength (< 15 km) of uplift with a mean of 1.2 meters per 1000 years and peak surface uplift at 1.6 meters per 1000 years. Another interpretation proposes the possibility of at least three shorter wavelength features. The shorter wavelength is likely associated to deformation in the upper crust. This study associates the crustal deformation to Quaternary movement along retro-wedge thrust faults at depth, which indicates active crustal shortening in Timor region.

Debate persists on the timing, magnitude and style of crustal shortening, uplift and basin evolution in the Andes. Many studies suggest that the central Andes, including the Altiplano plateau, were gradually uplifted as a result of protracted Cenozoic retroarc shortening. However, recent isotopic studies conclude that the Andes instead rose in pulses, with the most significant event occurring at 10-6 Ma. Many researchers attribute these rapid pulses of uplift to lower lithosphere delamination events. A better understanding of the history of Cenozoic crustal shortening is essential for determination of the mechanism(s) of Andean uplift. The well-exposed Cenozoic San Jerónimo Group was studied in the Ayaviri basin of the northern Altiplano in southern Peru. The 3-5 km-thick succession is situated at 3900-4800 m elevation, between the Western Cordillera magmatic arc and the Eastern Cordillera fold-thrust-belt. New detrital zircon U-Pb geochronological results from four sandstones and one reworked tuff in the San Jerónimo succession show large age populations indicative of syndepositional volcanism between approximately 38 and 27 Ma. A 1600-m-thick magnetostratigraphic section further constrains the depositional timing and accumulation rate of the upper portion of the succession. Sedimentological observations show a rapid transition from cross-stratified braided-fluvial sandstones to proximal channel-fill and alluvial-fan conglomerates at ~30 Ma. Paleocurrent measurements show important temporal and spatial variations in sediment dispersal patterns while conglomerate clast counts show an upsection transition from almost exclusively volcanic input to increasing contributions of clastic, quartzite, and limestone detritus. The corresponding shifts in depositional environment and sediment provenance are attributed to the activation of new thrust structures in close proximity to the basin, namely the Pucapuca-Sorapata fault system, indicating the presence of an eastward advancing fold-thrust belt dating to at least 38 Ma and reaching the Ayaviri basin within the northern Altiplano plateau at ~30 Ma. / text