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The Jehol Biota is famous for its diversity of Early Cretaceous fossils preserved under large amounts of pyroclastic materials. However, the precise determination on the ages of volcanoclas...

Several competing hypotheses have been proposed to explain east-west extension observed across the Himalayan orogen, based primarily on observations from the western and central Himalaya. They make predictions for the temporal and spatial patterns of deformation in the eastern Himalaya. These tectonic models include radial spreading or oroclinal bending of the Himalayan arc, oblique convergence of the Indian continent, tearing or lateral detachment of the Indian slab and eastward flow of lithosphere. Here, for the first time we constrain the activity history of the Cona rift, the only north-trending rift currently recognized in the eastern Himalaya, based on biotite and K-feldspar 40Ar/39Ar and zircon and apatite (U–Th)/He thermochronology, to evaluate these proposed rifting mechanisms. Low-temperature thermochronological results suggest that the Cona rift is the youngest rift system in the Himalayas: after a slow phase of exhumation since ∼14 Ma (∼0.2–0.13 mm/yr), normal faulting initiated here at ∼3.0–2.3 Ma with a fault slip rate of ∼3.8–1.6 mm/yr and a horizontal extension magnitude of ∼2–5 km. Analysis of rifting across the Himalayas shows that rift initiation ages young eastward, which is matched by eastward decreasing rift-extension magnitudes. Monotonically eastward younging rift development is consistent with the tectonic model involving eastward lithospheric flow driven by Indian slab dynamics and coupled asynchronous gravitational potential energy gradients.

The formation of the Yarlung Tsangpo river system is commonly thought to be controlled by tectonic processes initiated several million years ago. However, climate change may also play an important role in guiding drainage evolution. Here we reconstruct the drainage history of the Yarlung Tsangpo Gorge using field observations, age constraints from optically stimulated luminescence and radiocarbon dating, paleosalinity reconstruction and grain size analysis of lacustrine deposits, and river valley characteristics. Field observations, clay boron-derived paleosalinity reconstruction and grain size analysis of lacustrine deposits demonstrate that a closed inland saline lake existed upstream of the Yarlung Tsangpo Gorge, implying that cutting of the gorge postdated this paleolake. Optically stimulated luminescence and radiocarbon dating suggest that the paleolake formed at least 51 ka and terminated after ~13 ka. With a shift in global climate following the Last Glacial Maximum, the paleolake drained by river capture, and the gorge entrenchment commenced at the village of Jiala northwest of the Namche Barwa peak, approximately 13–10 ka ago. The evolution of the Yarlung Tsangpo occurred on a remarkably short timescale of just tens of thousands of years. In response to drainage system reorganization, the Yarlung Tsangpo incised at an average rate of at least 26 mm/yr. The rapid fluvial incision initiated at Jiala ~13 ka ago propagated rapidly upstream at ~2.12 m/yr. The Yarlung Tsangpo knickpoint has not stabilized, but will likely continue to migrate upstream.

We conducted biotite 40Ar/39Ar thermochronological research in the eastern Himalayan syntaxis and the neighboring Mesozoic and early Cenozoic Gangdese batholith belt with the aim of exploring the overall cooling pattern and thermal evolution of this remote region in the Himalayan orogen. A compilation of our newly acquired ages with existing data reveals a new temporal-spatial pattern. First, a temporal gap at 13–7 Ma exists in the cooling history of the study area, with ages 13 Ma in the Gangdese belt. The gap could be a manifestation of a renewed rapid cooling of the syntaxis since ∼7 Ma within a general region of slow cooling. Second, the isochron contours of the cooling ages have an annulus shape, with a younging trend toward the Namche Barwa–Gyala Peri peaks at the core of the syntaxis at 7–4 and 4–2 Ma and along the margins of the syntaxis at 2–1 Ma. This pattern may be a result of a regionally progressive cooling from the margin to the core of the syntaxi...

We determined detailed U–Pb ages for zircons in migmatitic granites densely exposed in the Namche Barwa peak (NBP) area, the core area of the eastern Himalayan syntaxis (EHS). The cores of these zircons show ages ranging from 863 to 1,256 Ma, with high Th/U ratios. These ages correspond to the crystallization age of the Proterozoic Indian continental basement. The majority of zircon rims from these migmatitic granites yield a significant age peak at about 8 Ma with an increase in Th/U ratios, suggesting that a large-scale partial crustal melting event occurred at 8 Ma in the NBP area. Because thermochronologic results have demonstrated that a rapid denudation started around 8 Ma, we interpret this large-scale partial melting of the crust as a decompression melting caused by rapid denudation in the NBP area. The rapid denudation at 8 Ma probably resulted from the combination of tectonic activities and surface erosion.

In this paper, we report thermochronological data from the southwest slope of Namche Barwa Peak, the core region of the eastern Himalayan syntaxis. The data include apatite fission track (AFT) ages of ten bedrock samples ranging from 0.5 ± 0.1 to 3.5 ± 0.5 Myr and biotite 40Ar/39Ar ages from 2.53 ± 0.14 to 5.57 ± 0.19 Myr, corresponding to elevations from 5370 to 3060 m. These ages are characterized by inverted age-elevation relationships (AERs), and the AERs of the AFT ages and the biotite 40Ar/39Ar ages are approximately parallel. Numerical modeling suggests that a possible change in the surface topography or faulting in this region could not have led to the observed inverted AERs. These observed ages demonstrate that a field of nonuniform exhumation rates existed in the relatively shallow crust (above the 110 °C isotherm) of the Namche Barwa Peak region. The exhumation rates increase significantly from 0.3 km/Myr to 5 km/Myr with increasing proximity to the peak. However, the exhumation rates in the relatively deep crust (below the 110 °C isotherm) of the same area are uniform at approximately 1.7 km/Myr. This distinctive exhumation field and the strong spatial correlation between the intense glacial erosion and high rock exhumation rate of Namche Barwa Peak suggest that glacial erosion most likely drives the rapid exhumation of Namche Barwa Peak.

Based on metamorphic studies of the Yadong high-pressure (HP) granulite and multiple thermochronological investigations of granitoids from both upper and lower parts, the Yadong section in the eastern Himalaya constrains the Cenozoic tectonic evolution of the Greater Himalayan Sequence (GHS). The Yadong HP granulite, located at the top of the GHS, underwent a peak-stage HP granulite facies metamorphism and two stages of retrograde metamorphism. Granulite and hornblende facies retrograde metamorphism took place at 48.5 and 31.8 Ma, respectively, marking the time of exhumation of the subducted Indian slab to lower and middle crustal levels. Subsequently, an average young zircon U–Pb age obtained from the Yadong HP granulite indicated that this unit was captured by its surroundings in a partially molten condition at 16.9 Ma. In addition, three granitoids from both the lower and the upper parts of the GHS yielded biotite 40Ar/39Ar ages of 11.0, 11.3, and 11.5 million years. These consistent ages suggest that ...