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The Beyşehir-Hoyran-Hadim Nappes crop out over 700km, from east to west in the Pisidian and Central Taurus Mountains of southern Turkey. During this study, field obsevations of lithological, structural and sedimentological features are combined with igneous geochemical data derived from samples collected to help redefine a series of tectono-stratigraphic units and also determine the origin of the Beyşehir-Hoyran-Hadim Nappes. Above a regionally autochthonous Tauride carbonate platform, the Beyşehir-Hoyran Nappes begin with Ophiolitic Melange, consisting of blocks of neritic and pelagic limestone, basalt, serpentinite, radiolarian chert and, in places, amphibolite-grade metamorphic sole-type rocks, together set in a highly sheared siltstone and mudstone matrix. Locally, large slices of serpentinized harzburgite are incorporated in the melange. The peridotite sheets include lenses of chromitite and dunite and are cut by a series of dolerite dykes. The higher thrust sheets in the Hadim area begin with the Korualan Unit; a thrust sheet (ca. 400m thick) of mainly redeposited carbonates, quartzose sandstones and mudstones of Mid-Late Triassic age, interpreted as a proximal slope/base-of-slope succession. Regionally above is the Huğlu-type Unit; a thrust sheet (ca. 1 km thick) of Mid-Late Triassic intermediate-acidic extrusives, volcaniclastics and minor pelagic carbonates, interpreted as a continental rift. Post-rift subsidence in this thrust sheet is recorded by thin (<100m thick) Upper Triassic-Upper Cretaceous pelagic carbonate and radiolarian chert, depositionally above. The uppermost thrust sheet, the Boyali Tepe-type Unit, comprises broken formation and melange, including Jurassic shallow-water carbonate, Ammonitico Rosso condensed pelagic limestone, radiolarian chert and Upper Cretaceous pelagic limestone, representing a Bahaman-type carbonate platform which subsided in Early Jurassic time. Anastomosing zones of tectonic-sedimentary melange separate these higher units. The Beyşehir-Hoyran Nappes document Triassic rifting and Jurassic-Cretaceous passive margin subsidence bordering the Northern Neotethyan Ocean. The Late Cretaceous harzburgitic ophiolite probably formed above a northerly dipping subduction zone within the Neotethyan ocean basin. Ophiolitic melange formed along the leading edge of the overiding plate. The ophiolite was emplaced southwards onto the northern margin of the Tauride platform in latest Cretaceous time, probably during collision of the passive margin with a trench. The nappe pile and underlying platform (Hadim Nappe) were thrust ca. 150km further south in Late Eocene time during regional continental collision and suture zone tightening. Several alternative palaeo-tectonic models are considered and tested in the light of data presented from this study. Assuming ‘in-sequence’ thrusting, the Beyşehir-Hoyran Nappes restore to a location north of a northerly Neotethyan spreading axis. More probably, they originated near the south margin of the northern Neotethys, but reached their position by ‘out-of-sequence thrusting’. Formation within a localised southerly strand of the northern Neotethys (Inner Tauride ocean) is more probable than within the main Neotethys further north. Wider implications for the Tethyan ocean as a whole and several other orogenic belts are also considered.

The Indo-Asian orogen is the world’s largest region of high topography, which affects both regional climate and mammalian speciation. How and when it achieved modern elevations and crustal thicknesses remains controversial, though there is agreement that ~40-50 Ma collision between India and Asia led to widespread crustal thickening and some amount of elevation gain since that time. Development of pre-collisional topography, the structural mechanisms of crustal thickening since collision, and the role of mantle lithosphere removal in producing elevation gain are common processes by which we interpret the topographic history of the orogen. In chapter 2, I address pre-collisional topography by reconstructing crustal volume before collision using total plate convergence estimates since 40 Ma. Results show that modern crustal volumes are 30% less than those estimated for 40 Ma using a pre-collisional crustal thickness of ~40 km (global average). I argue that this imbalance can be eliminated if the majority of Asian and Indian crust now found within the boundaries of the orogen was 23-32 km thick and consequentially at low elevations prior to collision. Chapter 3 focuses on mechanisms of recent faulting from a rare occurrence of thrusting at high elevation in the Guaizi Liang of the northern Tibetan Plateau. (~5000 m asl). We document 9 km (20%) shortening since Pliocene time and Quaternary shortening rates of 1.7 mm/yr based on balanced cross-sections and 36Cl cosmogenic radionuclide dating of a folded alluvial surface. Observed structural trends suggest that thrust faulting is related to simple shear between the Altyn Tagh and Kunlun/Manyi strike-slip faults, which need not produce crustal thickening. In chapter 4, I investigate the modification of the mantle lithosphere through a compilation of new and published geochemistry data from volcanic rocks across the plateau. I interpret slab flattening to have occurred at 40-30 Ma to drive widespread metasomatism of the Asian lithospheric mantle by melts from subducted Indian sediments. Removal of the slab at 30 Ma generated widespread volcanism across the plateau and likely thinned or removed them mantle lithosphere. Termination of volcanism in the southern Tibetan Plateau suggests renewed Indian underthrusting since 15 Ma.

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.

The kinematics and architecture of orogenic systems may be heavily influenced by climate, but little research has focused on the long-term effects of glacial erosion on orogenesis. Low-temperature thermochronometry and subsidiary structural, earthquake relocation, and offshore seismic reflection data from the St. Elias orogen are the basis for a new architectural model and demonstrate an association between glacial denudation and orogenic evolution. These data show that exhumation and deformation within the St. Elias orogen are focused across a thin-skinned fold and thrust belt on the windward flank, whereas the leeward flank functions as a deformational backstop. A previously unrecognized structure beneath the Bagley ice field separates these domains with south-side-up motion. This structure is interpreted to be a backthrust, making the orogen doubly-vergent. Suggestive of accelerated fault motion in response to climate change, bedrock cooling rates within the hanging wall of the backthrust and across the entire subaerial wedge accelerated ~ten-fold coeval with the onset of intense glacial conditions. Within the orogenic wedge, the zone of highest Quaternary exhumation (5 km/myr (±25%)) is focused around a narrow zone where the glacial equilibrium line altitude (ELA) intersects mean topography. This zone of rapid exhumation, not present prior to the onset of intense glacial conditions, cuts across the structural trend of the orogen and is more narrowly focused than the zone of orographic precipitation. Augmented glacial erosion around glacial ELA also coincided with a regional shift in deformation away from prominent forethrusts including the North American-Yakutat terrane suture (Chugach St. Elias fault) and the seaward deformation front (Pamplona zone). Accelerated denudation across the subaerial wedge thus appears to have forced the redistribution of strain along the backthrust and a series of forethrusts that lie beneath the zone of highest glacial flux, which in turn are systematically truncated by the backthrust. In a cause and effect response, the expansion of glaciers therefore appears to have resulted in an orogen scale structural reorganization and a narrowing of the orogenic wedge to preserve topographic slope. The focusing of long-term erosion around glacial ELA and the structural response of the orogenic wedge to Cenozoic climate change have not previously been observed in a real-world orogenic system and imply a high degree of coupling between climate and tectonics in this glacially-dominated orogen.