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The New Guinea region evolved within the obliquely and rapidly converging Australian and Pacific plate boundary zone. It is arguably one of the most tectonically complex regions of the world, and its geodynamic evolution involved microplate formation and rotation, lithospheric rupture to form ocean basins, arc-continent collision, subduction polarity reversal, collisional orogenesis, ophiolite obduction, and exhumation of (ultra)high-pressure metamorphic rocks. We describe the major onshore and offshore tectonic and geologic components, including plate boundaries, seismicity, faults, and magmatism, and we integrate these with emerging ideas about mantle dynamics to evaluate the Cenozoic tectonic evolution of New Guinea. Future research opportunities to resolve the mantle structure beneath New Guinea will enable mantle dynamics to be linked to lithospheric and surface processes. Virtually all plate tectonic and mantle processes have been active in the New Guinea region throughout the Cenozoic, and, as such, its tectonic evolution has global significance.

Apatite fission track thermochronology (AFTT) on granitic samples collected in the central Alaska Range in conjunction with geologic constraints from basins to the north (Nenana Basin) and south (Cook Inlet) of the range is used to constrain the timing, amount, rate, and pattern of surface uplift, rock uplift, and denudation since the late Miocene. The conversion from a thermal frame of reference (apatite fission track data) to an absolute frame of reference (with respect to mean sea level), which requires constraining the paleoland surface elevation, the paleomean annual temperature, and the paleogeothermal gradient, is evaluated and shown to be viable in the context of an exhumed apatite partial annealing zone (PAZ). Apatite ages at Denali (Mount McKinley) range from 16 Ma near the summit (∼6 km elevation) to 4 Ma at ∼2 km elevation. A distinctive break in slope in the apatite age profile at an elevation of 4.5 km, also marked by a change in confined track length distributions, marks the base of an exhumed apatite PAZ. Rock uplift and denudation are greatest at Denali, decreasing southward away from the McKinley strand of the Denali fault system as shown by progressively older apatite ages (7–35 Ma) from a suite of samples along the Kahiltna Glacier. A correlative decrease in topography occurs southward from the fault. The central Alaska Range lies within an arc defined by the Denali fault, with the highest peaks (including Denali) concentrated at the arc apex. Patterns of rock uplift and denudation within the central Alaska Range mimic topography. Between early and late Miocene, and possibly earlier, the central Alaska Range was most likely an area of relative tectonic and thermal stability. Rock uplift, denudation, and mean surface uplift of the Denali region began by the Late Miocene (∼5–6 Ma), being ∼8.5 km, ∼5.7 km, and ∼2.8 km, respectively, at average rates of ∼1.5 km/m.y., ∼1 km/m.y., and ∼0.5 km/m.y. The amount of rock uplift, denudation, and surface uplift decreases to ∼3 km, ∼2 km, and ∼1 km at Little Switzerland, some 45 km south of the Denali fault. We conclude that the topographic and rock uplift patterns of the central Alaska Range, the shape and proximity of the McKinley strand of the Denali Fault to these patterns, the timing of the onset of rock uplift and denudation at ∼5–6 Ma, and a significant change in relative plate motion between North America and the Pacific plates circa 5.6 Ma are all inherently related.

As lithospheric plates are subducted, rocks are metamorphosed under high-pressure and ultrahigh-pressure conditions to produce eclogites and eclogite facies metamorphic rocks. Because chemical equilibrium is rarely fully achieved, eclogites may preserve in their distinctive mineral assemblages and textures a record of the pressures, temperatures and deformation the rock was subjected to during subduction and subsequent exhumation. Radioactive parent-daughter isotopic variations within minerals reveal the timing of these events. Here we present in situ zircon U/Pb ion microprobe data that dates the timing of eclogite facies metamorphism in eastern Papua New Guinea at 4.3 +/- 0.4 Myr ago, making this the youngest documented eclogite exposed at the Earth's surface. Eclogite exhumation from depths of approximately 75 km was extremely rapid and occurred at plate tectonic rates (cm yr(-1)). The eclogite was exhumed within a portion of the obliquely convergent Australian-Pacific plate boundary zone, in an extending region located west of the Woodlark basin sea floor spreading centre. Such rapid exhumation (> 1 cm yr(-1)) of high-pressure and, we infer, ultrahigh-pressure rocks is facilitated by extension within transient plate boundary zones associated with rapid oblique plate convergence.